bluuebunny/crossref_metadata_2025 huggingface dataset:
Mapping of the full profile of T cell allorecognition regions on HLA‐DR2β subunit
Authors: Ulrich Robert G. , Zouhair Atassi M.
Published: March 2007

Alloreactive human T cell lines were developed by repeated in vitro restimulation with alternate allogeneic cells of similar DR2 serotype, but differing at other HLA loci. These polyclonal T cells recognized DR specificities in common with all DR2 serotypes. The allorecognition profiles of DR2β by the T cell lines were mapped by consecutive uniform‐sized overlapping peptides encompassing the entire extracellular and intracellular regions of the DRP subunit. It was found that the T cell allorecognition sites are focused around the first and third polymorphic regions of the N‐terminal domain, and interestingly, include conserved areas in the DRβ second domain as well as the intracellular segment β222–237. These findings have important implications for allorecognition. Comparison with the previous analysis of antibody‐binding regions of DR2β revealed some similarities and differences in the antibody and T cell alloresponses to this histocompatibility antigen.
Autoimmune diseases linked to abnormal K+ channel expression in double‐negative CD4−CD8− T cells
Authors: George Chandy K. , Cahalan Michael D. , Grissmer Stephan
Published: March 2007

Using the patch‐clamp technique in combination with fluorescence microscopy we have found an abnormality in voltage‐gated K+ channel expression in T cells that represents the first molecular marker linking three disparate autoimmune diseases in mice. CD4−CD8−Thy‐1.2+ (double‐negative or DN) lymphocytes from every known murine model for systemic lupus erythematosus, type‐1 diabetes mellitus and experimental allergic encephalomyelitis exhibit abnormally high numbers of an unusual K+ channel, termed type l compared to their phenotypic counterparts in normal mice. Other T cell subsets from these diseased mice retain their normal pattern of K+ channel expression. The unique K+ channel phenotype of DN T cells arises in parallel with the onset of autoimmunity. Although mitogen‐activated T cells and rapidly proliferating thymocytes exhibit large numbers of K+ channels, these channels are of an electrophysiologically distinct type called n. Thus, abundant expression of type l K+ channels appears to be a useful marker for DN T cells associated with autoimmunity and may provide a valuable tool for delineating the role of DN T cells in the pathogenesis of autoimmune diseases.
Serological analysis of the dissociation process of HLA‐B and C class I molecules
Authors: Gille Anne C. , Pérarnau Béatrice , Mercier Pierre , Lemonnier François A.
Published: March 2007

Two forms of HLA class I molecules reacting differentially with the HC‐10 monoclonal antibody were identified at the surface of HLA‐A3, B7, Cw3 or Cw7 human cells. The HC‐10‐nonreactive form (which includes all HLA‐A3 and a large fraction of HLA‐B7, Cw3 and or Cw7 molecules) corresponds to heavy chains apparently tightly associated to β2‐microglobulin. The HC‐10‐reactive form (which represents only a fraction of cell surface expressed HLA‐B7, Cw3 and Cw7 molecules) corresponds to heavy chains loosely but still associated to β2‐microglobulin. Further biochemical analyses and the study of mouse transfected cells expressing other HLA class I specificities led to the following conclusions: (a) dissociation of HLA‐B and C molecules is a multistep phenomenon, the various stages being identifiable serologically; (b) acquisition of the HC‐10 antigenic determinant appears as a hallmark of HLA class I molecules engaged in the process of dissociation; however, its expression does not imply complete separation of heavy and light chains; (c) only the initial stage of the dissociation process can be identified on cell surfaces, whereas (d) following addition of detergent, dissociation of HLA‐B and C molecules spontaneously proceeds further, resulting in accumulation in cell lysate of cell surface‐derived isolated HLA‐B and C class I heavy chains.
Induction of T cell activation by monoclonal antibodies specific for the transferrin receptor
Authors: Cano Eva , Pizarro Angel , Redondo Juan Miguel , Sánchez‐Madrid Francisco , Bernabeu Carmelo , Fresno Manuel
Published: March 2007

The effect of the monoclonal antibodies (mAb), FG 1/5, FG 1/6 and FG 2/12, specific for different epitopes of the transferrin receptor (TfR) on T cell activation was studied. mAb FG 1/6 but not FG 2/12 or FG 1/5 was able to induce T cell proliferation in presence of submitogenic doses of phorbol esters. The costimulatory effect of FG 1/6 was seen only with phorbol esters known to be activators of protein kinase C. This proliferation occurred at low concentration (0.5 μg/ml) of antibody, required the simultaneous presence of both stimuli, phorbol esters and FG 1/6, and was independent of the presence of accessory cells. Furthermore, FG 1/6 mAb was able to increase the rate of modulation of CD3 surface expression induced by phorbol esters. FG 1/6 induced interleukin (IL) 2 synthesis by normal and transformed T lymphocytes. In addition, anti‐IL 2 receptor antibodies inhibited FG 1/6 plus phorbol ester‐induced proliferation. Our results indicate that FG 1/6 mAb may provide to the T cells complementary signals to protein kinase C and that this activation is mediated by the IL 2/IL 2R pathway.
Surface receptors and immune activity of purified human circulating mononuclear cells V. Circulating null cells and a factor secreted by the null cells inhibit the synthesis of receptors for Fcμ by T cells in culture
Authors: Richter Maxwell , Kamran Mohammad , Jodouin Carol‐Ann
Published: March 2007

Receptors for Fcμ (FcμR) were not detected on freshly isolated unfractionated circulating human mononuclear cells (MNC) or purified T cells. However, a significant percentage of the T cells (20% to 40%), but not of the unfractionated MNC, exhibited Fcμ receptors following culture for 24 h at 37 °C in medium enriched with fetal calf serum. These receptors were newly synthesized by the T cells since they were not detected on T cells cultured for 24 h with cycloheximide in a non‐cytotoxic concentration. The absence of FcμR on the cultured unfractionated MNC (of which 70% are T cells) suggested that non‐T cells within the MNC — B cells and/or null cells and/or monocytes suppressed the synthesis of FcμR by the T cells. These cells were individually assayed for their capacity to suppress FcμR synthesis by co‐cultured T cells. The null cells were able to totally suppress FcμR synthesis whereas the B cells and monocytes exhibited no suppressive activity. Null cells cultured for 24 h at 37 °C secreted a factor which inhibited the synthesis of receptors for Fcμ by the cultured T cells. This factor is referred to as receptor synthesis suppressor factor or RSSF. On the basis of these findings, it is concluded that (a) the circulating T cells do not possess FcμR; these receptors are synthesized de novo by the T cells in culture, (b) the null cells, but neither the B cells nor the monocytes, suppress the synthesis of the FcμR by the T cells and (c) the null cells, but neither the B cells nor the monocytes, secrete a factor, receptor synthesis suppressor factor, which can suppress the synthesis of FcμR by the T cells.
Individual variation in the frequency of HLA class II‐specific cytotoxic T lymphocyte precursors
Authors: Man Stephen , Lechler Robert I. , Richard Batchelor J. , Sharrock Claire E. M.
Published: March 2007

The frequencies of HLA class II‐specific cytotoxic T lymphocyte precursors (CTLp) were studied in number of unrelated individuals using a limiting dilution analysis system optimized for the detection of CD4+ CTLp. Peripheral blood mononuclear cells (PBMC) were enriched for CD4+ T cells by immunomagnetic depletion of CD8+ T cells. In some allogeneic combinations high CTLp frequencies were obtained with no significant difference between PBMC and CD4‐enriched PBMC populations. In other combinations CTLp frequencies in CD4‐enriched PBMC were found to be at least twentyfold lower than in the starting, unfractionated PBMC, suggesting a predominance in these pairs of CD8+ CTLp. In addition there was variation in CTLp frequencies against the same set of HLA class II gene products between individuals, and variation in CTLp frequencies against different HLA class II gene products within individuals. The HLA class II specificity of the assay system was demonstrated unequivocally with detection of CTLp against HLA‐DR1 expressed on a murine L cell transfectant.
Characteristics of peptides which compete for presented antigen‐binding sites on antigen‐presenting cells
Authors: Smolenski Lori A. , Kaumaya Pravin , Zouhair Atassi M. , Pierce Susan K.
Published: March 2007

The T cell recognition of globular protein antigens requires the cell surface presentation of the protein by Ia‐expressing antigen‐presenting cells (APC). The mechanisms by which APC function remain to be elucidated. To gain a better understanding of association of antigen with APC surfaces, a large panel of peptides of diverse physicochemical properties was assayed for the ability to compete with presented antigen for binding sites on the APC surface. Competition was measured by the ability of a peptide to block the I‐Ek‐restricted T cell response to pigeon cytochrome c (Pc) as presented by APC. The panel assayed included overlapping peptides representing the entire length of sperm whale myoglobin and the α and β chains of human adult hemoglobin as well as synthetic conformational peptides of lactate dehydrogenase C4 exhibiting stable secondary, α‐helical structures. The results presented hereshow that several peptides of this group compete with the presented form of Pc forbinding sites on the APC. However, there is no single biochemical property or amino acid sequence algorithm which predicts the blocking ability. The peptides which compete with presented Pc are not predicted to assume the amphipathic α‐helical conformation hypothesized by De Lisi and Berzofsky (Proc. Natl. Acad. Sci. USA 1986. 82: 7048) for T cell antigenic peptides. However, peptides designed and synthesized to adopt a stable α‐helical secondary structure show more potent blocking activity than the corresponding linear peptides, suggesting that the secondary structure may indeed be a contributing factor in the ability of presented antigenic peptides to be bound by the APC. The results with the myoglobin and hemoglobin peptides show no connection between any particular secondary structure of the peptide in the native proteins and the ability of the peptides to block presentation. Further, there is no correlation between the major histocompatibility complex restriction of the competing peptides and their ability to block the I‐Ek‐restricted Pc‐specific T cell response. This suggests that antigen presented by the APC may be bound to APC structures other than Ia prior to association with Ia. Such additional binding sites for presentedantigen may be necessary to facilitate association with Ia.
Tumor necrosis factor‐α and interleukin 6 synergistically induce T cell growth
Authors: Kuhweide Rudolf , van Damme Jo , Ceuppens Jan L.
Published: March 2007

T cells stimulated with phytohemagglutinin are dependent on monocyte‐derived helper signals (e.g. interleukin (IL) 6 and IL 1) for their proliferation. In the present study the effect of recombinant tumor necrosis factor α (rTNF‐α) as a helper signal for growth of highly purified peripheral blood human T cells stimulated with phytohemagglutinin was examined. TNF‐α alone had a weak co‐stimulatory effect, while a combination of TNF‐α and IL 6 provided highly effective synergistic helper signals for T cell proliferation. The effect of TNF‐α could not be ascribed to secondary induction of IL 1 production. The effect of TNF‐α on T cell proliferation was also found to be independent of the autocrine T cell growth factors IL 2 and IL 4. This latter points to dissimilarity between IL 1 and TNF‐α in the mechanism by which each of these two cytokines in combination with IL 6promotes T cell proliferation. TNF‐α, IL 6 and IL 1 thus seem to follow different pathways in their function as helper signals in T cell activation.
A spontaneous hybridoma producing autoanti‐idiotypic antibodies that recognizea Vx−associated idiotope in mercury‐induced autoimmunity
Authors: Guéry Jean‐charles , Druet Philippe
Published: March 2007

Anti‐idiotypic (Id) antibodies have been suggested to play a role in the self regulation process observed in Brown‐Norway rats developing mercury‐inducedautoimmunity. However, the presence of such antibodies has not yet been directly demonstrated. For that purpose, spleen cells from a mercury‐injected rat were fused and the resulting hybridomas tested for their anti‐Id activity against monoclonal anti‐glomerular basement membrane (GBM) antibodies produced in this model. A monoclonal antibody (mAb) was obtained that specifically reacted in an enzyme‐linked immunosorbent assay with an anti‐GBM mAb and to a much lesser extent with another one produced in the same fusion. In Western blot experiments this autoanti‐Id mAb reacted under reducing conditions with the χ L chains but not with the H chains of the two anti‐GBM mAb. It did not react with the χ L chains of eight other rat mAb. This mAb is therefore an autoanti‐Id mAb that recognizes a Vx−associated Id expressed on two anti‐GBM mAb. These results demonstrate that anti‐GBM antibodies and their corresponding autoanti‐Id antibodies are simultaneously produced during this disease. Whether or not these autoanti‐Id antibodies have a regulatory and/or a pathogenic role in this disease remains to be established.
Selective loss of T cell functions in different stages of HIV infection Early loss ofanti‐CD3‐induced T cell proliferation followed by decreased anti‐CD3‐induced cytotoxic T lymphocyte generation in AIDS‐related complex and AIDS
Authors: Gruters Rob A. , Terpstra Fokke G. , de Jong Rolien , Van Noesel Carel J. M. , Van Lier René A. W. , Miedema Frank
Published: March 2007

To investigate the effects of persistant human immunodeficiency virus (HIV) infectionon T cell reactivity, functional properties of peripheral blood T cells from HIV‐seropositive homosexual men in various stages of infection were studied. T cell activationvia CD3 resulting in proliferation and differentiation was measured in a model system independent of accessory cells, using immobilized anti‐CD3 monoclonal antibodies (mAb). T cells from HIV‐infected asymptomatic men had a decreased proliferative response compared to HIV‐negative controls. T cells from AIDS‐related complex (ARC) and AIDS patients, compared to T cells from asymptomatic HIV‐infected men, had a significantly lower proliferative response to anti‐CD3 mAb. This diminished response to anti‐CD3 mAb was shown to be due to decreased interleukin (IL)2 productionand could be enhanced by co‐stimulation with anti‐CD28 mAb or by adding IL2. Anti‐CD3‐induced generation of cytotoxic T lymphocytes was fully intact in early infection but was severely decreased in T cells from ARC and AIDS patients. Cytotoxic activity could be restored to near normal levels after co‐stimulation with either anti‐CD28 mAb or IL2. Our data demonstrate a differential loss of T cell functions in the course of HIV infection which is predominantly caused by a lack of IL2 production after stimulation via the CD3/T cell receptor complex. In early HIV infection this seems to be predominantly caused by a specific loss of memory T cells. However, in later stages of infection when both naive and memory T cell subsets are depleted, resultingin a normal naive/memory T cell ratio, T cell functions further deteriorate probably due to intrinsic activation defects. These findings may be of pathogenic relevance since diminished T cell reactivity may facilitate spreading and replication of virulent HIV variants heralding development of ARC and AIDS.
Complement‐dependent antibody‐mediated cytotoxicity in the spontaneously diabetic BB/OK rat: association with β cell volume density
Authors: Hehmke Bernd , Lucke Silke , Schröder Dieter , Klöting Ingrid , Kohnert Klaus‐dieter
Published: March 2007

The present study examined in the spontaneously diabetic BB/OK rat whether a relationship exists between the appearance of complement‐dependent antibody‐mediated cytotoxicity (C'AMC) in serum and the relative β cell volume density determined in pancreatic biopsies. C'AMC was estimated by 51Cr release from prelabeled major histocompatibility complex‐compatible neonatal rat islet cells afterexposure to rat serum and rabbit complement. Fifty‐one percent (72/141) of sera from BB/OK rats with newly diagnosed diabetes were positive for C'AMC. At onset of hyperglycemia, insulin‐immunoreactive β cells were only detectable in pancreas biopsies of 25% (10/40) of the BB/OK rats who displayed mild hyperglycemia(plasma glucose 8.3—13.0 mmol/l) and low serum C'AMC. A twofold increase (p < 0.01) of C'AMC and loss of the remaining β cells was evident in untreated animals upon their reexamination within 1 week after diagnosis of hyperglycemia. Initiation of insulin therapy prevented neither the increase in C'AMC activity nor the decrease in the β cell volume density. In contrast, three out of four mildly hyperglycemic BB/OK rats treated with cyclosporin A maintained both their initial C'AMC levels and relative β cell volume density not only throughout the treatment period (4 weeks) but also for at least 4 weeks thereafter. In one additional animal receiving cyclosporin A no protection of the remaining β cells could be achieved and C'AMC levels were markedly increased.

It is concluded that the appearance of increased C'AMC in serum may reflect autoimmune reactions against the islet β cells of spontaneously diabetic BB/OK rats. Theincrease of C'AMC seen in untreated as well as insulin‐treated BB/OK rats, whichwere even devoid of β cells, suggests that C'AMC activity appears secondary to the loss of β cells. These results do not support the hypothesis of a direct β cell destruction via intrainsular complement activation.
Hyporesponsiveness of “naive” (CD45RA+) human T cells to multiple receptor‐mediated stimuli but augmentation of responses by co‐stimuli
Authors: Horgan Kevin J. , Van Seventer Gijs A. , Shimizu Yoji , Shaw Stephen
Published: March 2007

Much remains to be clarified regarding the functional capacities of the two major reciprocal subsets of human CD4+ cells which we interpret to be naive and memory cells. CD4+ naive (CD45RA+, LFA‐3−) and memory (CD45R0+, LFA‐3+) cells were rigorously purified by immunomagnetic negative selection. Their proliferation was measured in response to four protocols of receptor‐mediated activation: soluble anti‐CD3 mAb, plastic‐immobilized anti‐CD3 mAb, activating pairs of anti‐CD2 mAb, and “superantigens” staphyloccocal entero‐toxins A and B (SEA and SEB). Naive cells proliferated much less than memory cells to each of these four regimens although their capacity to respond was demonstrated by strong PHA‐induced proliferation. Although three of the regimens depend on autologous monocytes, poorer naive cell responses are also observed to anti‐CD3 mAb immobilized on plastic in the absence of monocytes; this implies an intrinsic hyporesponsiveness of naive cells, independent of theirpotentially weaker interaction with monocytes. Naive cells proliferated less than memory cells to superantigens SEA and SEB over a wide dose range; this assumes particular importance because such superantigens are believed to more closely mimic antigen‐specific stimulation than anti‐CD3 mAb. The possibility was explored that hyporesponsiveness of naive cells reflects the fact that naive cells require additional co‐stimuli to facilitate their activation. In support of this concept, we observed that proliferation of naive cells to anti‐CD3 mAb and SEA or SEB (but not to anti‐CD2 mAb pairs) was consistently enhanced by pre‐activation of monocytes present in the culture. Naive cell proliferative responses were augmented further in cultures supplemented with interleukin (IL) 1β and IL 6 or exposed to the co‐stimulating mAb anti‐CD28 and anti‐CD44. The pattern of augmentation was dependent on the specific triggering regimen: anti‐CD44 mAb was particularly effective in augmenting the response to superantigens, anti‐CD28 mAb for the anti‐CD3 response and IL 1β/IL 6 for that induced by anti‐CD2 mAb pairs. With particular combinations of stimulus/co‐stimuli naive cell proliferation was as strong as that of memory cells. We interpret these findings to indicate that naive cells are capable of responding to antigen, but that such responses are critically dependent on the available co‐stimuli in vivo.
Down‐regulation of CD5 mRNA in B‐chronic lymphocytic leukemia cells by differentiation‐inducing agents
Authors: Gignac Suzanne M. , Buschle Michael , Victor Hoffbrand A. , Drexler Hans G.
Published: March 2007

Most B chronic lymphocytic leukemia (CLL) cells express on their surface the CD5 antigen which is an activation marker on normal B cells. To investigate the control of CD5 expression in B‐CLL cells, we examined several inducing agents for their effects on CD5 mRNA expression. Northern blot analysis demonstrated that the expression of CD5 mRNA could be up‐ or down‐regulated depending on the inducers used. Treatment with direct activators of protein kinase C (PKC), the phorbol ester phorbol 12‐myristate 13‐acetate (PMA) or the natural agent bryostatin 1 (Bryo), caused increased CD5 mRNA expression after 8—16 h of incubation. In contrast, exposure to the dual signals of a PKC activator (PMA or Bryo) plus the calcium ionophore A23187 led to down‐regulation of CD5 mRNA expression. The molecular alterations at the RNA level were accompanied by morphological changes: PMA and/or Bryo induced cellular features of activation while PMA plus A23187 or Bryo plus A23187 mediated morphological changes indicativeof differentiation to plasmacytoid cells. The data suggest that as a consequence of maturation differentiated B‐CLL cells down‐regulate CD5 expression by analogy with the normal ontogenic process in which plasma cells, the end‐stage cells of normal B cell differentiation, are CD5−.
Tumor necrosis factor inhibitor: purification, NH2−terminal amino acidsequence and evidence for anti‐inflammatory and immunomodulatory activities
Authors: Seckinger Philippe , Vey Elisabeth , Turcatti Gerardo , Wingfield Paul , Dayer Jean‐Michel
Published: March 2007

The urine of some febrile patients has been shown to contain a tumor necrosis factor‐alpha‐inhibiting activity (TNF‐α INH) when tested in a cytotoxicity assay using the TNF‐susceptible cell line L‐929. The inhibitor was purified to homogeneity using a simple three‐step procedure which included a TNF‐α affinity column, cation exchange and reverse‐phase chromatography. TheNH2−terminal amino acid sequence of the inhibitor showed no sequence similarity with proteins in the data bases used. Using gel filtration, it was shown that TNF‐α and the inhibitor form a stable complex which eluted with a molecular weight of about 75000. This value corresponds to the sum of the inhibitor (∼︁ 30000) andTNF‐α (∼︁45000–50000) molecular weight. The TNF‐α INH blocked prostaglandin E2 production by dermal fibroblasts in a dose‐dependent manner, providing evidence for antiinflammatory activity. TNF‐α INH also blocked class I antigen expression in a dose‐dependent manner as measured using the human Colo 205 tumor cell line. Furthermore, TNF‐α INH affected TNF‐α synergism with IFN‐γ‐induced HLA‐DR antigen expression but had no effect on IFN‐γ activity. The data presented demonstrate that TNF‐γ bioactivity can be regulated at the protein level.
Inhibition of lipopolysaccharide‐induced in vitro desensitization by interferon‐γ
Authors: Haas Jürgen G. , Meyer Nicolette , Riethmüller Gert , Ziegler‐heitbrock H. W. Löms
Published: March 2007

Exposure of Mono‐Mac‐6 cells to lipopolysaccharide (LPS) can induce rapid and transient expression of cytokines like tumor necrosis factor (TNF), interleukin 1 and interleukin 6. Preculture of Mono‐Mac‐6 cells in culture medium containing small amounts (1—50 ng/ml) of LPS for 3 days leads to an unresponsiveness to a subsequent stimulation with a high amount of LPS. This in vivo, desensitization of a monocytic cell line may serve as a model for desensitization to LPS seen in vivo, for example in mice or man repetitively treated with LPS. Addition of interferon‐γ (IFN‐γ) to the Mono‐Mac‐6 cells during the LPS preculture period leads to an inhibition of desensitization, whereas addition of IFN‐α or IFN‐β is not able to inhibit the LPS‐induced desensitization. The inhibition of desensitization by IFN‐γ was dose dependent and time dependent. Preculture of Mono‐Mac‐6 cells with LPS leads to a strong reduction of TNF mRNA. This reduction of specific mRNA is also overcome by addition of IFN‐γ, but not by IFN‐α and IFN‐β, indicating that pretranslational mechanisms are responsible for the regulation of TNF in desensitization.
Abnormal anti‐viral immune response in mice is corrected in HLA‐B27.2‐transgenic mice
Authors: Kievits Femia , Lokhorst Wil , Ivanyi Pavol
Published: March 2007

In contrast to the strong Sendai virus‐specific cytotoxic T‐lymphocyte (CTL) responses in C57BL/6 mice, H‐2Kb mutant bm1 mice are nonresponders to Sendai virus. By appropriate crossings between HLA‐B27 double‐transgenic mice and Kb mutant bm1 mice, and after subsequent selection, H2bm1 homozygous mice were produced expressing the human HLA‐B27.2 and β2−microglobulin genes. Here we show that the introduction of a human HLA classI gene into the genome of the H2bm1 Sendai virus‐nonresponder mutant mice resulted in good responsiveness to Sendai virus, and in normal levels of Sendai virus‐specific CTL precursors. The CTL response in the HLA‐B27.2 double‐transgenic H2bm1 mice against Sendai virus was restricted by the HLA‐B27.2 molecule. These results show the direct involvement of HLA class I molecules inregulation of the anti‐viral CTL repertoire and represent for the first time a correction of abnormal anti‐viral immunity in mice by incorporation of a human MHC class I (HLA‐B27.2) gene.
Lymphocyte‐mediated inhibition of platelet cytotoxic functions during Hymenoptera venom desensitization: characterization of a suppressive lymphokine
Authors: Tsicopoulos Anne , Tonnel André‐bernard , Vorng Han , Joseph Michel , Wallaert Benoit , Kusnierz Jean‐pierre , Pestel Joël , Capron André
Published: March 2007

Recently, it has been shown that platelets, through a receptor for the Fc fragment of IgE, could be specially triggered by venom allergens in hypersensitivity to hymenoptera, generating cytocidal mediators toward Schistosoma mansoni larvae, and oxygen metabolites measured by chemiluminescence. After rush immunotherapy, a depressed platelet response was demonstrated to be associated with the production of lymphokine(s). Here we report the characterization of a factor present in supernatants of antigen‐stimulated T cells from patients after hymenoptera venom desensitization which is able to inhibit platelet cytotoxic functions in a dose‐dependent manner. The optimal inhibition was observed with supernatants obtained after T lymphocyte stimulated with 10−5 μg venom allergen/ml. Once specifically produced the platelet‐suppressive effect of lymphocyte supernatants was not antigen specific. The producing T cell subpopulation was identified as CD8+. This lymphokine had an approximate molecularmass of 25 kDa and a pI of 4.8. It was heat and acid stable and sensitive to trypsin and proteinase K but not to neuraminidase. This platelet inhibitory activity was absorbed by platelet membrane suggesting its binding to a receptor. These properties were very similar to a previously described platelet activity suppressive lymphokine, suggesting the participation of this lymphokine in the mechanisms of rush desensitization.
Analysis of T cell receptor Vβ gene usage in primary mixed lymphocyte reactions : evidence for directive usage by different antigen‐presenting cells and Mls‐like determinants on T cell blasts
Authors: Larsson‐sciard Eva‐lotta , Spetz‐hagberg Anna‐lena , Casrouge Armanda , Kourilsky Philippe
Published: March 2007

The usage of four different T cell receptor (TcR) Vβ gene families within normal, non‐primed T cell populations in response to various types of antigen‐presenting cells (APC) in primary mixed lymphocyte reaction has been studied. We demonstrate that distinct patterns of Vβ gene usage are obtained within a given T cell population in response to different types of APC with the same allo‐H2. When responder T cells are stimulated with one type of allogeneic APC, from various H2‐disparate mice, the same Vβ gene preference is observed. Furthermore, when H2‐ and Mls‐mismatched APC gene used as stimulators, the Mls‐associated Vβ6 and Vβ8.1 gene families are highly elevated in response to both B and T cell blasts from certain Mls‐positive strains. The results demonstrate that different types of allogeneic APC have the capacity to generate biases in TcR Vβ gene usage and imply that functional Mls‐like determinants are presented by T cell blasts. The findings are discussed with respect to TcR‐major histocompatibility complex interactions in allostimulation.
Autoreactive T cells in normal mice: unrestricted recognition of self peptides on dendritic cell I‐A molecules by CD4−CD8− T cell receptor α/β+ T cell clones expressing V β8.1 gene segments
Authors: Seman Michel , Boudaly Sarah , Roger Thierry , Morisset Jean , Pham Ghislaine
Published: March 2007

CD4−CD8− double‐negative (DN) and CD4+CD8− T cell clones were derived from splenic precursors resistent to killing by anti‐Thy‐1, ‐CD5, ‐CD4 and ‐CD8 monoclonal antibodies and complement. Both DN and CD4+ clones express functional T cellreceptor (TcR) α/β and exhibit strong autoreactivity in vitro. DN cells can be induced to proliferate by dendritic cells (DC) of all haplotypes tested, although this activation is inhibited by antibodies specific for I‐A determinants expressed on the stimulatory DC. In contrast, CD4+ clones only respond to syngeneic or I‐Ad−compatible DC. Both DN and CD4+ autoreactive clones do not proliferate when cultured with class II+ H‐2d normal or tumor macrophages and B cell lines or with class II‐transfected L cells, suggesting that these cells recognize self peptides only present on the surface ofDC. Despite their phenotype resembling that of immature thymocytes and their inability tointeract directly with B lymphocytes, DN cloned T cells, like CD4+ T cells, exhibit nonspecific helper functions and can induce polyclonal B cell proliferation and differentiation. DN TcR α/β+ peripheral T cells represent, like TcR γ/δ+ lymphocytes, a new T cell subset physiological role whose remains to be defined.
Bovine γ globulin‐specific CD4+ T cells are retained by bovine γ‐globulin‐tolerant mice*
Authors: Burtles Sally S. , Taylor Roger B. , Hooper D. Craig
Published: March 2007

Immunological tolerance is an acquired state of antigen‐specific nonresponsiveness which is generally attributed to either the deletion or suppression of tolerogen‐specific T helper cell clones. Unresponsiveness to xenogeneic immunoglobulins can be readily induced and has been extensively studied in order to ascertain the means by whichtolerance is established and maintained. As an absence of reactivity to foreign immunoglobulin has been noted in situations where suppressor cell activity was minimized, this tolerant state has often been ascribed to clonal deletion. The present study demonstrates that bovine γ‐globulin (BGG)‐tolerant mice are unable to generate humoral responses to BGG in vivo and yet harbor BGG‐specific CD4+CD8− T cells which can divide and secrete interleukin 2 when stimulated in vitro. Indeed, the in vitro reactivity to BGG of these cells exceeded that of a similar population of non‐immune cells. This is in direct opposition to the loss of response that would be expected if clonal deletion were operative. The presence of BGG‐specific CD4+ T cells, which appear to be at least partly primed, in mice unresponsive to BGG, indicates that tolerance to BGG is likely to be dependent on unidentified immunoregulatory processes rather than clonal deletion.
Characterization of γ/δ T cell clones isolated from human fetal liverand thymus
Authors: Carding Simon R. , McNamara James G. , Pan Mary , Bottomly Kim
Published: March 2007

The origin and development of T cells bearing γ/δ T cell receptors (TcR) has been extensively studied in the mouse. By contrast, little is known about development patterns and diversity of the human γ/δ T cell lineage. To study therepertoire of human γ/δ+ T cells during T cell ontogeny, wehave isolated clonal populations of γ/δ+ T cells from 14‐week fetal thymus and liver and characterized the molecular compositionof their TcR.

The technique of in situ hybridization was used to identify cells expressing TcR genes in fetal liver and thymus. A panel of clones representative of developing T cell populations found in vivo was subsequently isolated from both tissues and clones expressing cell surface γ/δ receptors were identified. Although both the liver‐derived γ/δ+ T cell clone, L2, and the thymus‐derived γ/δ+ T cell clone, T6, had similar cell surface phenotypes, namely CD3+, CD7+, CD45+ and CD8−, their reactivity with anti‐CD2 and ‐CD4 antibodies was different. L2 was CD2high, CD4− whereas T6 was CD2low, CD4low. Both clones possessed effector functions similar to those of adult T cells as demonstrated by the synthesis and secretion of cytokines in response to stimulation through the CD3/TcR complex. Analysis of the TcR composition of the fetal clones showed both clones to possess similar or identical γ chain components, Cγ1, Jγ1/2, Vγ8, and both utilize Vδ gene segments other than Vδ1. This TcR genotype has not been previously reported in the analysis of adult γ/δ+ T cells. Our studies have identified a unique population of human γ/δ+ T cells that may be derived extrathymically and appear to be preferentially and perhaps transiently expressed during fetal life.
Development of cytoplasmic CD3+/T cell receptor‐negative cells in the peripheral lymphoid tissues of chickens
Authors: Pat Bucy R. , Chen Chen‐Io H. , Cooper Max D.
Published: March 2007

In a study of T cell ontogeny using monoclonal antibodies specific for chicken T cellreceptors (TcR) and associated cell surface molecules, we found a subset of lymphocytes that express cytoplasmic CD3 epitopes in the absence of cell surface CD3/TcR complexes. Approximately half of these cells, which were present in the spleen, bursa and intestine of young chick embryos, expressed surface CD8. None expressed CD4, TcR1 (γ/δ), TcR 2 (α/β) or TcR 3 (a third CD3‐associated heterodimer inthe chicken). These cytoplasmic CD3+CD8± cells, tentatively named TcR 0 cells to denote their lack of surface TcR, appeared first in the spleen of 8‐day embryos, 4 days before TcR expression begins in the thymus, and reached a peak frequency of ≈︁ 10% of the splenic cell in 14‐day embryos. The TcR 0 cells were alsopresent in adult birds, where they comprised only about 1% of the CD3+ spleen cells and approximately 40% of the lymphocytes in the intestinal epithelium. We conclude that the avian TcR 0 cells represent a thymus‐independent lineage of lymphocytes which, like natural killer cells in mammals, may play an important role in body defense.
The role of functionally distinct helper T lymphocyte subpopulations in the inductionof human B cell differentiation
Authors: Sleasman John W. , Morimoto Chikao , Schlossman Stuart F. , Tedder Thomas F.
Published: March 2007

Human helper T lymphocytes can be dissected into two functionally distinct subpopulations based on expression of the CD45RA (2H4) or CD45R0 (UCHL‐1) surface antigens. While both subpopulations are able to induce equivalent levels of B cell activation and proliferation, only the CD4+CD45RA− subpopulation is capable of inducing B cell differentiation in pokeweed mitogen (PWM)‐stimulated cultures. To define the mechanism responsible for the dichotomy between induction of proliferation and differentiation by the two CD4+ subpopulations, we examined the abilities of the purified T cell subpopulations to produce lymphokine mRNA following T cell activation. Northern analysis revealed that both subpopulations produced interleukin (IL) 2 and interferon (IFN)‐γ mRNA following PWM activation. The CD4+CD45RA− subpopulation, however, produced higher levels of IFN‐γ mRNA and the CD4+CD45RA+ cells produced higher levels of IL 2 mRNA. Neither subpopulation elaborated detectable mRNA for IL 4, IL 5 or IL 6. Of greatest significance was that the addition of recombinant or T cell‐derived lymphokines could not compensate for the inability of the CD4+CD45RA+ subpopulation to induce B cell differentiation in PWM assays. Direct T‐B cell contact was required for the optimal induction B cell differentiation in these assays, suggesting that CD4+CD45RA+ T cells were deficient in their abilityto directly deliver the T cell‐B cell signals required for B cell differentiation. These results suggest that the differential abililty of the two subpopulations of CD4+ T cells to induce B cell differentiation does not result from differences inlymphokines elaborated, but may result from differences in their abilities to interact directly with B cells to initiate differentiation.
Limited number of immunoglobulin VH regions expressed in the mutant rabbit “Alicia”
Authors: Dipietro Luisa A. , Short Jeffery A. , Zhai Shi Kang , Kelus Andrew S. , Meier Daniel , Knight Katherine L.
Published: March 2007

A unique feature of rabbit Ig is the presence of VH region allotypic specificities. In normal rabbits, more than 80% of circulating immunoglobulin molecules bear theVHa allotypic specificities, a1, a2 or a3; the remaining 10% to 20% of immunoglobulin molecules lack VHa allotypic specificities and are designated VHa−. A mutant rabbit designated Alicia, in contrast, has predominantly serumimmunoglobulin molecules that lack the VHa allotypic specificities (Kelus and Weiss, Proc. Natl. Acad. Sci. USA 1986. 83: 4883). To study the nature and molecular complexity of VHa− molecules, we cloned and determined the nucleotide sequence of seven cDNA prepared from splenic RNA of an Alicia rabbit. Six ofthe clones appeared to encode VHa− molecules; the framework regions encoded by these clones were remarkably similar to each other, each having an unusual insertion of four amino acids at position 10. This insertion of four amino acids has beenseen in only 2 of 54 sequenced rabbit VH genes. The similarity of the sequences of the six VHa− clones to each other and their dissimilarity to most other VH genes leads us to suggest that the VHa− molecules in Alicia rabbits are derived predominantly from one or a small number of very similar VH genes. Such preferential utilization of a small number of VH genes may explain the allelic inheritance of VH allotypes.
Defects in signal transduction caused by a T cell receptor β chain substitution
Authors: Reno Toufic A. , Ley Steven , Sugiyama Eiji , Cantagrel Alain , Blumberg Richard , Bonventre Joseph , Terhorst Cox , Yeh Edward T. H.
Published: March 2007

An antigen‐specific T‐T hybridoma was mutagenized with ethylmethane sulfonate and negatively selected by anti‐Ly‐6 antibody‐induced growth inhibition. One of the mutants generated, M4/8, had lost surface expression of a T cell receptor (TcR) Vβ8 epitope detected on the surface of the parental cell line. However, the mutant cell line did express high levels of TcR heterodimer as detected with a pan‐specific anti‐TcR antibody. CD3 ϵ, Ly‐6 and Thy‐1 were expressed at levels similar to the wild‐type parental cell line. Analysis of the surface TcR/CD3 complexes by immunoprecipitation and two‐dimension gel electrophoresis confirmed that the major discernable difference between the wild‐type and mutant TcR/CD3 complexes resided in the TcR β chain. The parental cell line had the potential to express two TcR heterodimers, VαVβ1 and VαVβ8, as determined by Northern blot analysis. Co‐modulation experiments suggested that both types of receptors were expressed. However, the VαVβ8 receptor was the predominant form. In contrast, the mutant M4/8 cell line did not synthesize Vβ8 mRNA and, thus, only the VαVβ1 TcR was synthesized. Despite the normal surface expression of TcR/CD3 complex, the M4/8 mutant cell line did not produce interleukin 2 (IL2) in response to antigen or soluble anti‐CD3 ϵ monoclonal antibody (mAb). Furthermore, it responded poorly to concanavalin A, phytohemagglutinin and anti‐Ly‐6 mAb. Cross‐linking of the stimulatory antibodies partially restored the IL 2 response to anti‐CD3 ϵ or anti‐Ly‐6 to wild‐type levels. Phorbol ester and ionomycin stimulated a full IL 2 response in the M4/8 cell line, demonstrating that the defect in the decreased signaling in the mutant did not result from a defect in the IL2 gene program. In conclusion, these data suggested that the pairing of α/β heterodimer not only determined antigen/MHC specificity but also the signaling efficiency of the TcR/CD3 complex.
T cell receptor Vβ genes expressed by IgG anti‐DNA autoantibody‐inducing T cells in lupus nephritis: Forbidden receptors and double‐negative T cells
Authors: Adams Sharlene , Zordan Tracy , Sainis Krishna , Datta Syamal K.
Published: March 2007

In the (SWR × NZB)F1 (SNF1) model of lupus nephritis, pathogenic variety of IgG anti‐DNA autoantibodies are induced by certain T helper (Th) cells that are either CD4+ or CD4−CD8− (double negative; DN) in phenotype. From the spleens of eight SNF1 mice with lupus nephritis, 149 T cell lines were derived and out of these only 25 lines (≈ 17%) were capable of augmenting the production of pathogenic anti‐DNA autoantibodies. Herein, we analyzed the T cell receptor (TcR) Vβ genes used by 16 such pathogenic autoantibody‐inducing Th cell lines. Twelve of the Th lines were CD4+ and among these five lines expressed Vβ8 (8.2 or 8.3). The Vβ8 gene family is contributed by the NZB parent to the SNF1 mice, since it is absent in the SWR parental strain. Three other CD4+ Th lines expressed Vβ4, another was Vβ2+ and one line with poor autoantibody‐inducing capability expressed Vβ1. Four autoantibody‐inducing Th lines from the SNF1 mice had a DN phenotype and these lines were also autoreactive, proliferating in response to syngeneic spleen cells. Among these DN Th lines, two expressed Vβ6 and one expressed Vβ8.1 TcR. Both of these are forbidden TcR directed against Mls‐1a (Mlsa) autoantigens expressed by the SNF1 mice and such autoreactive T cells should have been deleted during thymic ontogeny. Thus, the DN Th cells of non‐lpr SNF1 mice are different from the DN cells or MRL‐lpr which lack helper activity and do not express forbidden TcR. The spleens of 6 out of 19 nephritic SNF1 animals tested also showed an expansion of forbidden autoreactive TcR+ cells that were mainly DN. Two of these animals expressed high levels of Vβ6 (anti‐Mlsa) and Vβ11 (anti‐I‐E) TcR+ cells, three others had high levels of Vβ11+ cells alone and one animal had an expanded population of Vβ17a+ (anti‐I‐E) cells. The I‐E‐reactive TcR again should have been eliminated in the SNF1 thymus, since they express I‐E molecules contributed by the NZB parent. The SWR parents of SNF1, are I‐E−; moreover, they lack the Vβ11 gene but they express Vβ17a in peripheral T cells. Whereas the NZB parents are I‐E+, they lack a functional Vβ17a gene and they delete mature Vβ11+ T cells. Thus, a combination of MHC class II and TcR genes inherited from the NZB and SWR parents and abnormalities in thymic deletion/selection processes may generate the autoantibody‐inducing Th cells in the SNF1 mice.
Analysis of thymus‐independent type 2 antigen uptake by marginal zone macrophages in thin slices of viable lymphoid tissue in vitro
Authors: Cha David , MacPherson G. Gordon
Published: March 2007

There is evidence to suggest that the B cell population in the marginal zone (MZ) of the spleen is responsible for the antibody response to thymus‐independent type 2 antigens (TI‐2). The macrophage (MΦ) population in the MZ has been shown to take up TI‐2 antigens selectively, and this uptake is potentially important in understanding antigen handling in TI‐2 responses. Uptake has not been studied in vitro because isolation of MZ MΦ completely abrogates uptake. We have adapted a technique for cutting thin slices of viable spleen which retained this MΦ function under in vitro conditions and allowed manipulation of the system. This technique may have widespread application in the study of tissue MΦ which are difficult to isolate. Using this method, we show that MZ MΦ in splenic slices in vitro selectively take up a TI‐2 antigen, in a way apparently identical to that seen in vivo. This is not due to high pinocytic activity by these cells nor to their anatomical location. We provide evidence for a receptor‐mediated uptake system, whose function is sensitive to collagenase. The ligand specificity of the uptake system showed unexpected cross‐reactivity with the mannosyl‐fucosyl receptor with high affinity for mannan, but was not identical to it, and may be indicative of the natural ligands for the TI‐2 antigen uptake system.
Cyclosporin A inhibits rat mast cell activation
Authors: Dráberová L'Ubica
Published: March 2007

To gain further insight into the mechanism of immunosuppression by cyclosporin A (CyA), the effect of CyA on activation of isolated rat mast cells was studied. CyA alone, up to a concentration of 80 μM, had no effect on histamine release from unstimulated mast cells in both calcium‐supplemented and calcium‐free media. However, in the presence of extracellular calcium CyA inhibited, in a dose‐dependent manner (range from 8 nM to 80 μM), histamine release induced by three unrelated secretagogues, the compound 48/80, calcium ionophore A23187 and concanavalin A plus phosphatidylserine. In the absence of extracellular calcium no, or only a marginal, effect of CyA on histamine release induced by the secretagogues was observed. CyA also inhibited the uptake of radiolabeled calcium by the secretagogues‐treated cells. However, CyA did not interfere with the activation‐related early increase in the intracellular free calcium. Thus, CyA‐mediated inhibition of mast cell activation is related to external calcium uptake. These results indicate that rat mast cells belong to the immune cell types whose activity can be modulated by physiologically relevant concentrations of CyA.
The ontogeny of human lymphocyte recirculation: high endothelial cell antigen (HECA‐452) and CD44 homing receptor expression in the development of the immune system
Authors: Horst Eveliene , Meijer Chris J. L. M. , Duijvestijn Adrian M. , Hartwig Nico , Van Der Harten Hans J. , Pals Steven T.
Published: March 2007

In the present report we have studied the expression of a lymphocyte homing receptor, the CD44 antigen, and of HECA‐452, a high endothelial‐specific antigen, during the development of the human immune system. We found that prothymocyte immigrants of the thymus already expressed the CD44 antigen. Similarly, the first peripheral T lymphocytes in fetal lymph nodes, tonsils and gut‐associated lymphoid tissue were also CD44+. Cortical thymocytes and germinal center cells were CD44−. CD44 antigen expression was, thus, not limited to mature recirculating lymphocytes. This suggests that CD44 may not only be involved in recirculation of mature lymphocytes but also in the migration of prothymocytes to their site of maturation, i.e. the thymus. High endothelial venules (HEV) were not demonstrable at the early onset of lymphocyte immigration into the developing lymphoid organs. However, when large‐scale influx of lymphocytes occurred, it paralleled HEV development. HECA‐452 antigen expression preceded the morphological transformation of endothelium into a HEV phenotype. Expression of this antigen therefore, independently reflected the specialized nature of high endothelium. In a patient with complete DiGeorge's syndrome normal HEV developed, indicating that the presence of T lymphocytes is not a requirement for HEV development. Interestingly, a subpopulation of venules located in the thymic medulla near the corticomedullary junction expressed the HECA‐452 antigen. These vessels, which had flat or intermediately high endothelium, are probably involved in lymphocyte migration to the thymus.