bluuebunny/crossref_metadata_2025 huggingface dataset:
Activation of murine CD8+ lymphocytes: Two distinct signals regulate c‐myc and interleukin 2 receptor RNA expression
Authors: Hardt Conny
Published: March 2007

Resting cytotoxic T lymphocyte precursors (CTL‐P; CD8+) constitutively express T cell receptors (TcR) on their cell surfaces. CTL‐P are preactivated if binding of the corresponding antigen (mitogens, allogeneic major histocompatibility complex (MHC) determinants, viral proteins or haptens in conjunction with self MHC structures) to the TcR takes place. Using a myc specific probe I show that within 12 h antigen binding leads to optimal c‐myc RNA expression which seems to be the first sign that resting CTL‐P are preactivated. Thereafter, c‐myc RNA expression was remarkably reduced only at day 5. Antigen alone, however, is not sufficient for interleukin 2 receptor (IL 2R) RNA expression. A monocyte‐derived, soluble mediator termed IL 2R‐inducing factor (RIF) acts in conjunction with antigen to induce the expression of IL 2R RNA and functional IL 2R on the cell surface. RIF is a 44‐kDa heat‐labile protein produced by accessory cells and its function is restricted to CD8+ lymphocytes. IL 2R RNA is first expressed 12 h after onset of culture, maximally expressed on day 3 and it decreases thereafter. Cells kept in long‐term culture without mitogen but in the presence of IL 2 do not express high amounts of IL 2R RNA. Expression of IL 2R RNA can be very efficiently reinduced, however, by mitogenic stimulation. In contrast to primary cultures, IL 2R RNA expression peaks earlier and is independent of RIF. The results obtained here show that (a) for CD8+ lymphocytes of primary cultures two distinct activation signals (mitogen and RIF) are necessary for c‐myc and IL 2R RNA expression and (b) for CD8+ lymphocytes of secondary cultures the mitogenic signal alone is sufficient for re‐expression of IL 2R RNA.
Unusual forms of T cell γ mRNA in a human T cell leukemia cell line: Implications for γ gene expression
Authors: Tighe Lynette , Forster Alan , Clark David M. , Boylston Arthur W. , Lavenir Isabella , Rabbitts Terence H.
Published: March 2007

The expression and rearrangement of T cell rearranging (TRG) γ genes in human leukemic cell lines has been examined. The cell line MOLT‐17 produces abundant γ mRNA which is translated into a protein found on the cell surface which is associated with the CD3 molecule. The analysis of the γ mRNA sequences in MOLT‐17, by cDNA cloning, shows transcripts of aberrantly rearranged genes as well as the productively rearranged allele. The productive allele consists of a rearranged V 8 gene joined to Jγ2. Two forms of aberrant transcript originate from the other rearranged γ allele. One of these initiates just upstream of the unrearranged Jγ2 segment, and the other initiates from a Vγ8 gene segment joined to another Jγ segment, upstream of Jγ2. An unusual feature of the latter transcript is that polyadenlyation has occurred at the end of the first exon of Cγ2, where two conserved poly(A) addition signals occur. The MOLT‐4 cell line, on the other hand, has productively and nonproductively rearranged γ alleles, from which relatively little transcription occurs. These results define new Jγ segments in the human TRG γ locus and suggest that positive activation of the γ locus is necessary for high level transcription after rearrangement.
Abrogation of the lethal graft‐vs. ‐host reaction developed to non‐H‐2 antigens: involvement of T suppressor cells distinct from veto cells
Authors: Halle‐Pannenko Olga , Pritchard Linda L. , Bruley‐Rosset Martine
Published: March 2007

The mortality induced by graft‐vs.‐host reaction (GVHR) in (DBA/2 × B10.D2)F1 recipients transplanted with cells from H‐2d‐identical B10.D2 donors can be abrogated by preimmunizing the donors with parent‐strain spleen cells from normal DBA/2 mice. The experiments described here were designed to explore the possibility that the observed protection might be mediated by veto cells contained in the immunizing cell inoculum; the reasoning was based on an analogy with the cytotoxic T lymphocyte response to non‐H‐2 antigens where suppression can be mediated by veto cells, present in the spleens of normal mice, which are radiosensitive and largely Lyt‐2+. We show that the intensity of the protection against GVHR mortality is a function of the immunizing cell dose, and that protection remains effective when optimal doses of immunizing cells are (a) irradiated or (b) pretreated with anti‐Thy‐1 serum. GVHR suppression is abrogated when, before transfer to F1 recipients, suppressor cells from spleens of immunized donors are pretreated with antiserum directed against Lyt‐1.2 (expressed by B10.D2 but not by DBA/2, which expresses Lyt‐1.1); in contrast, it is not significantly affected when these same cells are pretreated with anti‐Lyt‐2.2 alloantiserum. We conclude that when the antigen load is great enough the immunizing cells play a largely passive role in the observed suppression. The protection against GVHR mortality seen in this H‐2‐compatible combination is transferable by Lyt‐1+2− suppressor T cells originating in mice given high doses of alloantigen. These suppressor cells are therefore distinct from the splenic veto T cells effective against cytotoxic T lymphocyte responses to non‐H‐2 antigens. The mechanism of the observed suppression and its relationship to Mlsa product(s) are discussed.
Differentiation of B cell progenitors in vitro: Generation of surface IgM+ B cells, including Ly‐1 B cells, from Thy‐l− asialoGM1+ cells in newborn liver
Authors: Hardy Richard R. , Kishimoto Tadamitsu , Hayakawa Kyoko
Published: March 2007

We have established a stromal adherent cell line (ST2) from fetal liver that promotes growth and differentiation of early B lineage cells. Many cells in the “null population” (3–5%) from newborn liver that lack antigens found on mature erythroid, myeloid or lymphoid cells proliferate extensively on this ST2 layer. Further division of this cell fraction on the basis of Thy‐1 and asialoGMl (aGMI) expression discriminates cells that predominantly proliferate from those that differentiate on the ST2 layer. Among four populations, Thy‐1+ aGM1− cells proliferate most but yield few B220+ cells. In contrast, Thy‐1− aGM1+ cells proliferate to a very limited extent, but most (> 90%) start to express B220 and a large fraction (up to 50%) become surface IgM+ after 2 weeks of culture. These B cells include cells expressing the pan‐T cell molecule Ly‐1, that is, Ly‐1 B cells. Curiously, this Thy‐1− aGM1+ cell population is largely absent from bone marrow in adult mice.
Selective effects of cholera toxin on the activation of mouse B cells by different polyclonal activators
Authors: Klaus Gerry G. B. , Vondy Karen , Holman Mary
Published: March 2007

Murine B cells were stimulated in vitro with anti‐immunoglobulin (Ig) antibodies, lipopolysaccharide, or with various combinations of phorbol dibutyrate and ionomycin. Very low concentrations (ca. 10−14 M) of cholera toxin inhibited anti‐Ig‐stimulated DNA synthesis, while the response to LPS was only abrogated by 2 × 104‐105‐fold greater concentrations of the toxin. Earlier responses in anti‐Ig‐stimulated B cells, such as increases in Ia antigen levels, were not affected by the toxin. Protein kinase C‐activating phorbol esters, together with Ca2+ ionophores, are believed to stimulate DNA synthesis in lymphocytes by mimicking the two second messengers resulting from ligation of the antigen receptors. However, concentrations of cholera toxin which totally abolish anti‐Ig‐induced B cell proliferation significantly enhanced DNA and RNA synthesis induced by phorbol dibutyrate plus ionomycin. The results are discussed in terms of possible effects of cholera toxin on guanine nucleotide‐binding (G) proteins controlling receptor coupling to second messenger‐generating systems in B cells.
HIV env glycoprotein shares a cross‐reacting epitope with a surface protein present on activated human monocytes and involved in antigen presentation
Authors: Beretta Alberto , Grassi Fabio , Pelagi Micaela , Clivio Alberto , Parravicini Carlo , Giovinazzo Giovanna , Andronico Franca , Lopalco Lucia , Verani Paola , Butto Stefano , Titti Fausto , Rossi Giovanni Battista , Viale Giovanna , Ginelli Enrico , Siccardi Antonio G.
Published: March 2007

A serological cross‐reactivity between env gp120 glycoprotein of the human immunodeficiency virus (HIV) and a human cellular surface protein has been defined by a monoclonal antibody (M38) raised against HIV. The cellular antigen is a protein of ca. 80 kDa expressed on a small fraction of mononuclear cells in peripheral blood and in lymph nodes. The protein behaves as an activation antigen of the monocytic lineage since it is expressed by monocytes in plastic‐adherent culture conditions and by interferon‐γ‐treated monocytes and pro‐monocytic U937 cells. The protein is involved in antigen presentation since the antibody efficiently inhibits the proliferation of responsive lymphocytes in autologous tetanus toxoid presentation assays. In the T lymphoblastoid line H9, the protein is present in very small amounts, is not induced by interferon‐γ and increases after HIV infection. Sera from lymphoadenopathy syndrome and acquired immunodeficiency syndrome (AIDS) patients fail to detect the cellular protein, although containing antibodies reacting with gp120. We propose that both viral and cellular structures recognized by the monoclonal antibody (mAb) are involved in interactions with CD4 molecules of T helper lymphocytes and that such molecular mimicry might be relevant in the pathology of HIV infection. This view is supported by the finding that BL/10T4, a CD4‐specific mAb, binds to M38 neutralizing its interactions with HIV and with monocytes. mAb M38 thus behaves as the internal image of CD4. This single property would explain all its diverse binding characteristics.
Activation of macaque T cells and B cells with agonistic monoclonal antibodies
Authors: Clark Edward A. , Draves Kevin E.
Published: March 2007

A series of mouse monoclonal antibodies (mAb) to human differentiation antigens known to have agonistic activity for human T or B cells was found to bind specifically to macaque T or B cell subsets. Most of these mAb also stimulated macaque lymphocyte proliferation, implying that they recognize functional homologues in monkeys. Anti‐CD3, anti‐CD28 (9.3), and anti‐Lp220 (CD45R) mAb stimulated proliferation of both human and macaque T cells; similarly, anti‐IgM and anti‐CDw40 mAb stimulated both human and macaque B cells. In contrast, anti‐CD20 and anti‐CD39 mAb, which are known to stimulate human B cells, did not stimulate macaque B cells. A human low‐molecular weight B cell growth factor (BCGF) and anti‐IgM were co‐stimulatory for macaque splenic B cells but not for blood B cells, suggesting that B cell subpopulations may differ in their responsiveness to BCGF. The results show that functional epitopes on some lymphocyte surface molecules such as CD28 or CDw40 are conserved in primate evolution. Functional epitopes on other cell surface molecules such as CD3 and CD20 may have more complex evolutionary constraints.
Impairment of immunogenicity by antigen presentation in liposomes made from dimyristoylphosphatidyl‐ethanolamine linked to the secretion of prostaglandins by macrophages
Authors: Bakouche Quahid , David François , Gerlier Denis
Published: March 2007

The induction of antibody response in syngeneic rats by the Gross virus cell surface antigen (GCSAa) was dependent on the presentation of GCSAa into liposomes made from distearoylphosphatidylcholine (DSPC). GCSAa liposomes made from dimyristoylphosphatidylethanolamine (DMPE) were nonimmunogenic, even when used as anamnestic immunogens. Spleen cells, from rats twice immunized with GCSAa‐DSPC‐liposomes and used to transfer the anti‐GCSAa immune response into naive recipients after a tertiary immunostimulation in vitro in the presence of naive peritoneal exudate cells (PEC), responded to soluble GCSAa only after irradiation at 500 rds and to GCSAa‐DMPE‐liposomes only when indomethacin was added during the in vitro stimulation. The preincubation of these cells with empty DMPE liposomes or the addition of supernatant from PEC fed with DMPE liposomes abrogated the response to GCSAa‐DSPC liposomes. Using a specific radioimmunoassay, prostaglandin E2 was demonstrated to be produced by PEC when fed with DMPE liposomes, and not when fed with DSPC liposomes. This prostaglandin E2 secretion by PEC induced by DMPE liposomes was inhibited by indomethacin.
Purified lymphocyte function‐associated antigen‐3 and T11 target structure are active in CD2‐mediated T cell stimulation
Authors: Tiefenthaler Georg , Hünig Thomas , Dustin Michael L. , Springer Timothy A. , Meuer Stefan C.
Published: March 2007

In this study we have used cells expressing LFA‐3 or T11TS, the human and sheep forms of the ligand of CD2, as well as the purified LFA‐3 and T11TS molecules themselves to study their effects on T cell activation via the CD2‐mediated “alternative pathway”. Sheep red blood cells, which bind to CD2 via T11TS in E‐rosette formation, and human autologous monocytes, which express the LFA‐3 molecule, both induce proliferation of resting T cells in the presence of per se submitogenic concentrations of anti‐T112 plus anti‐T113 monoclonal antibodies (mAb). This effect is blocked by mAb to LFA‐3, T11TS and CD2 known to inhibit CD2‐ligand interaction. In addition, purified LFA‐3 and T11TS, when added at ng amounts to cultures containing submitogenic concentrations of anti‐T112 + 3 mAb, are also strongly mitogenic for resting human T cells. Thus, both LFA‐3 and T11TS are potent co‐stimulators of the alternative pathway of T cell activation but by themselves do not provide a mitogenic signal. This finding is discussed with regard to a physiological role of CD2‐LFA‐3 interaction in T cell activation.
Anti‐interferon‐γ antibody protects mice against the generalized Shwartzman reaction
Authors: Billiau Alfons , Heremans Hubertine , Vandekerckhove Filip , Dillen Chris
Published: March 2007

A generalized Shwartzman reaction was found to occur in non‐SPF‐NMRI mice given a local injection of S. marcescens lipopolysaccharide (LPS) in the footpad, followed, with an interval of 24 h, by an i.v. injection. The reaction occurred several hours after the second injection. It was characterized by disseminated subcutaneous bleedings at the mouth, anus, conjuctiva, nose tip and tail end. Most mice died within 24–48 h. The size of the LPS dose given in the footpad (5 μg) was found to be critical in that the reaction failed to occur with higher as well as lower doses. The reaction was found to be completely absent in mice that had received one or more systemic injections of monoclonal antibodies with neutralizing potential for murine interferon‐γ (IFN‐γ). Mice treated with control preparations, including a monoclonal antibody with binding but no neutralizing activity for murine IFN‐γ, remained sensitive to induction of the reaction. These observations assign a crucial role to endogeneous IFN‐γ in the elicitation of the generalized Shwartzman reaction and open perspectives for the prevention or therapy of clinical conditions related to the Shwartzman reaction by the use of antibodies to IFN‐γ.
Alloreactive T cell clones transformed by Theileria parva retain cytolytic activity and antigen specificity
Authors: Baldwin Cynthia L. , Teale Alan J.
Published: March 2007

Theileria parva is a protozoan parasite which infects and transforms bovine lymphocytes. This study examined the effects of Theileria‐induced transformation on phenotype and function, in terms of cytolytic potency and specificity, of class I and class II‐specific alloreactive T cell clones. Alloreactive T cell clones infected with T. parva (Muguga) retained expression of the T cell differentiation antigens BoT2, BoT4, BoT8 and the mature T cell antigen recognized by monoclonal antibody ILA27, as well as cytolytic function and antigen specificity, over a period of 3–4 months in continuous culture. These features were identical to those expressed by the uninfected parent clones. During this period, neither antigenic stimulation nor exogenous growth factors were required for the maintenance of proliferation, function or antigen specificity. Thereafter, cytolytic activity declined and was eventually lost, which may reflect degenerative changes normally associated with T cell senescence rather than result from parasitization per se.
Identification and characterization of a novel membrane activation antigen with wide cellular distribution
Authors: Schulz Thomas F. , Mitterer Manfred , Vogetseder Werner , Böck Güinther , Myones Barry L. , Dierich Manfred P.
Published: March 2007

A monoclonal antibody, 7F7, raised against the Raji B lymphoblastoid cell line reacted with about 35% of peripheral blood B cells, germinal center B cells, follicular dendritic cells and some vascular endothelial cells. Although not found on resting T cells this antigen was strongly expressed on CD4+ and CD8+ T cells activated with phytohemagglutinin, pokeweed mitogen and anti‐T3, and its expression on B cells was enhanced after stimulation with pokeweed mitogen. It is strongly expressed 24 h after stimulation with phytohemagglutinin and its expression is reduced but not eliminated by cyclosporin A treatment. The molecule defined by antibody 7F7 is found on some, but not all, B cell lines, on an HTLV‐I‐transformed T cell line and on the promyelocytic cell line U937. Immunoprecipitation from externally and metabolically labeled Raji cells revealed a single‐chain molecule of 85 kDa.
Physiology of IgD IX. Effect of IgD on immunoglobulin production in young and old mice
Authors: Swenson Christina D. , Vollenhoven Ronald F. Van , Xue Bin , Siskind Gregory W. , Thorbecke G. Jeanette , Coico Richard F.
Published: March 2007

Weekly i.p. injections of IgD from birth in (SJL × BALB/c)F1 mice were found to accelerate the development of IgG‐ and IgA‐secreting cells and to increase the numbers of Ig‐secreting cells of all isotypes in 17–28‐day‐old mice, but not in 7–10‐day‐old mice. Similarly, repeated weekly injections of IgD in normal adult BALB/c mice increased the numbers of reverse plaque‐forming cells/spleen for all isotypes studied, including IgM, IgG1, IgG2, and IgA, but not for IgD itself. No such effect was observed in IgD‐treated aged (20 months old) BALB/c mice. The absence of an effect of IgD on Ig secretion appeared to correlate with a lack of induction of receptors for IgD on T cells of the host, both in 7–10‐day‐old and in aged mice. In 7–10‐day‐old mice this lack of induction appeared due to their very low numbers of L3T4+ T cells. A comparison was made between the effect of a single injection of IgD or lipopolysaccharide (LPS) on numbers of Ig‐secreting cells in the spleen determined 1–7 days after injection. Both agents caused increases, but the increase in IgM‐producing cells was much greater after LPS (day 4), while IgD caused a relatively greater increase in IgG2 and IgA (days 4–7). Increases in IgGl and IgG3‐producing cells induced by LPS and IgD were of similar magnitude (days 6–7). IgD production, however, was not increased. The number of cells producing antibody of anti‐trinitrophenyl (TNP) specificity was enhanced by LPS (day 4), but not by a single injection of IgD, although more than one injection of IgD caused a significant increase in anti‐TNP‐producing cells above background.

LPS, but not IgD, caused B cell proliferation in vitro in the presence or absence of γ ‐irradiated Tδ cells. However, in vivo, IgD injections caused a significant increase in the percentage of lymphoid follicles with germinal centers in lymph nodes from 17–21‐day‐old and normal adult mice, but not in 7–10‐day‐old or aged mice. Such an effect was also absent in 24–28‐day‐old mice, where germinal center development, even in untreated mice, was very high.
Regulatory activity of the human CD8+ cell subset: a comparison of CD8+ cells from the intestinal lamina propria and blood
Authors: Lee Alfred , Sugerman Harvey , Elson Charles O.
Published: March 2007

This study was done to better define the immunoregulatory mechanisms in the human intestinal lamina propria (LP). Peripheral blood (PB) and LP cells were obtained from patients having intestinal resections. CD4+ and CD8+ cell subsets were isolated using hybridoma antibodies in a panning technique. Graded numbers of LP and PB CD8+ cells were added to cultures of autologous fresh B cells plus CD4+ cells plus pokeweed mitogen. After 10 days incubation in vitro, the supernatants were collected, and IgM and IgA synthesis was measured by isotype‐specific sandwich ELSA. Both PB and LP CD8+ cells suppressed IgM and IgA synthesis by indicator cultures consisting of 5 × lo4 B cells plus 5 × 104 CD4+ cells to a comparable extent. However, when these same CD8+ cells were added to indicator cultures of 5 × 104 B cells plus 105 CD4+ cells, PB CD8+cells still suppressed, but LP CD8+cells enhanced IgM and IgA synthesis. LP but not PB CD8+cells also augmented IgM and IgA synthesis in cultures with suboptimal immunoglobulin synthesis. Despite these results, LP CD8+cells were not able to provide help for B cell immunoglobulin synthesis when these two cell types were cultured together with pokeweed mitogen. The mechanism of immunoglobulin augmentation by LP CD8+ cells appeared to involve antagonism of a CD4+rather than CD8+suppressor cells. We conclude that functional heterogeneity is more evident within the LP CD8+ subset, with both suppressor and contra‐suppressor activities demonstrable, with the latter representing a major activity in LP but not in PB CD8+cells.
The function of human intercellular adhesion molecule‐1 (ICAM‐1) in the generation of an immune response
Authors: Dougherty Graeme J. , Murdoch Sarah , Hogg Nancy
Published: March 2007

Monoclonal antibody RR1/1 directed against the putative LFA‐1 ligand molecule intracellular adhesion molecule‐1 (ICAM‐1) was found to inhibit the T cell prolifera‐tive response to the antigen PPD. Interestingly, the percentage of unstimulated monocytes which expressed ICAM‐1 on their surface appeared to vary greatly from person to person although the majority of monocytes did express high levels of ICAM‐1 within their cytoplasm and surface expression could be rapidly induced on most cells by adherence to fibronectin. Resting T cells showed no evidence of surface or cytoplasmic ICAM‐1 although expression was induced both within the cell and on the membrane as a result of activation with phytohemagglutinin or a combination of OKT3 and phorbol 12, 13‐dibutyrate. The significance of these findings with respect to the function of monocyte and T cell in the generation of an immune response is disussed.
Genetic regulation of multispecific antibody responsiveness: improvement of “high” and “low” characters
Authors: Mouton Denise , Siqueira Maria , Sant'Anna Osvaldo A. , Bouthiuier Yolande , Ibanez Olga , Ferreira Vera C. A. , Mevel Jean‐Claude , Reis Moema H. , Piatti Rosa Maria , Stiffel Claude , Biozzi Guido
Published: March 2007

The five selections carried out in the mouse for high or low antibody responsiveness to various multideterminant immunogens were successful. In all cases the large interline difference was shown to result from the additive effects of several independently segregating loci (polygenic regulation). However, important peculiarities were demonstrated in these original selections concerning either the cellular mechanisms operating or the effect of the selected genes on antibody responses to antigens unrelated with those used for the selection (multi‐specific effect). In an attempt to improve and generalize the effect of selection, the 5 high and the 5 low lines were inter‐crossed to obtain populations with a balanced proportion of the 5 genomes. These two populations were then submitted to selective breedings in which the phenotypic character was the weighted responses to pluri‐antigen immunization. The data obtained in 16 consecutive generations of two selective breedings (general‐primary, GP and general‐secondary, GS, responses) carried out from these populations are reported. The genetic parameters of the response to GP and GS selections are compared with those obtained in the original selections. The final result of both GP and GS selections demonstrate a marked improvement of the high and low antibody production traits, both quantitatively (interline divergence) and qualitatively (multi‐specific effect). The success of GP and GS selections agrees with the concept that distinct groups of genes are preferentially affected by selection according to the nature of the selection antigen and the immunization procedure.
Enhancement in Igha mouse strains of the “natural” suppressive activity of normal T splenocytes against the expression of Igh‐1b allotype. I. Molecular aspects of the chronic suppression obtained
Authors: Benaocb Philippe , Burdenave Guy
Published: March 2007

Several approaches have been used in our attempts to increase the “natural” ability of normal T splenocytes (Tn) from BALB/c or BC8 mice (both Igha ) to induce, in F1 hybrids, a suppression of Igh‐lb expression (IgG2a of b haplotype). These heterozygous F1 were produced by mating these Igha mice and their Ighb‐congenic partners (CB20 and C57BL/6, respectively). The most powerful approaches were to sensitize the Igha mice by either autologous splenocytes coated with Igh‐lb or B splenocytes from Ighb‐congenic mice. In F1 having paternally inherited the b haplotype the sensitized T splenocytes (Tn) prepared from such mice are able to induce, like Tn when injected at birth, a chronic suppression of Igh‐lb expression. However, the suppression was established with a much higher efficiency: already at 6 weeks of age in 100% of the F1 treated with 1 × 107 Ts vs. a final rate of 70% progressively reached only at 42 weeks of age in the F1 treated with 4 × 107 Ts. In F1 having maternally inherited Ighb the differences were even more pronounced than with 4 × 107 Tn i.e. the suppression induction was almost totally ineffective, whereas with 2 × 107−4 × 107 Ts a rate of 100% treated F1 subjected to suppression was reached at 19 weeks of age. As the productions of IgM, IgD and IgA of the b haplotype were not affected by the suppression, the Ts are believed to act on the Igh‐lb′ cells. Attempts were also made to induce allotypic suppression of other b allotypes by the use, as sensitizing cells, of myeloma cells carrying Igh‐6b (IgM of b haplotype). We failed in revealing any sign of a T cell reactivity against Igh‐6b similar to the reactivity against Igh‐lb. The use of Igh‐6b+ myeloma cells grown in an Igh′ or in an Igha background allowed us to assume that the cells responsible for the sensitization are, in the Ighb B lymphocyte population, either the Igh‐lb+ lymphocytes or the lymphocytes having passively adsorbed this allotype, or both.
Mycobacteria‐reactive Lyt‐2+ T cell lines
Authors: Libero Gennaro De , Flesch Inge , Kaufmann Stefan H. E.
Published: March 2007

The biological activities of mycobacteria‐reactive Lyt‐2+ T cells were characterized in vitro. T cells from mice immunized with killed Mycobacterium tuberculosis or viable M. bovis were restimulated in vitro and cloned under limiting dilution conditions. Several L3T4−Lyt‐2+ T cell lines, some of them KJ16+, were established. These T cell lines were capable of lysing mycobacteria‐primed macrophages in an antigen‐specific way. The cytolytic activity of some T cell lines was found to be class I restricted, whereas others showed antigen‐specific killing in the absence of apparent H‐2 restriction. Several T cell lines produced interferon‐γ after appropriate stimulation. Furthermore, these T cell lines could induce tuberculostatic macrophage capacities by apparently two different mechanisms, namely by secretion of lymphokines (most probably interferon‐γ) and by direct cell qontact. We conclude that CD8 T cells with antigen‐specific cytolytic potential are generated during tuberculosis and that these T cells are involved in the immune response to tubercle bacilli.
Human immune response to allergens of house dust mite, Dermatophagoides pteronyssinus. IV. Occurrence of natural autologous anti‐idiotypic antibodies
Authors: Saint‐Remy Jean‐Marie R. , Lebecque Serge J. , Lebrun Philippe M. , Jacqnemin Marc G.
Published: March 2007

IgG isolated from the plasma of seven individuals hypersensitive to the common house dust mite Dermatophagoides pteronyssinus (DPT) was exhaustively adsorbed onto insolubilized DPT. The unbound fraction was found by radioimmunoassay to contain antibodies recognizing the variable region of both anti‐DPT IgG and IgE antibodies. This recognition was idiotype (Id)‐specific as it persisted after passage over insolubilized polyclonal IgG of unrelated specificity.

Most of these anti‐Id IgG carried the internal image of the initial antigen in that they competitively inhibited the binding of anti‐DPT antibodies to DPT. Immunoadsorption of anti‐Id IgG onto insolubilized anti‐DPT IgG antibodies from the same individual completely eliminated their reaction with anti‐DPT IgG but not with anti‐DPT IgE, suggesting that idiotopes included in the antigen‐binding site of specific IgG and IgE antibodies were not identical. Anti‐Id IgG recognizing idiotopes located outside the antigen‐binding site (bystander idiotopes) were also completely removed by passage over insolubilized anti‐DPT IgG; in this case the reaction of the anti‐Id IgG with both anti‐DPT IgG and anti‐DPT IgE was inhibited, indicating that, for a given individual, bystander idiotopes were shared between anti‐DPT antibodies pertaining to these two isotypes.
Inhibition of the proliferative response of human B lymphocytes to B cell growth factor by transforming growth factor‐beta
Authors: Petit‐Koskas Elisabeth , Génot Elisabeth , Lawrence David , Kolb Jean‐Pierre
Published: March 2007

The effects of transforming growth factor‐beta (TGF‐β) on the proliferative response of human B cells to the low molecular weight B cell growth factor (BCGF) have been investigated in this study. It was found that TGF‐β”, at picomolar concentrations, strongly inhibited the BCGF‐induced proliferation of anti‐μ. chain or Staphylococcus aureus Cowan I‐activated human B cells and also of a BCGF‐dependent cell line derived from a human lymphocytic nodular lymphoma. This inhibitory effect was detected in normal and serum‐free culture conditions. The suppression was greatly reduced when TGF‐β was added to the culture one day after BCGF and could be reverted by removing TGF‐β from the culture medium. Since TGF‐β has been detected in supernatants from activated T cells, this factor may represent an important regulatory molecule in the feedback control of B cell activation.
Correlated expression of surface antigens in human thymocytes. Evidence of class IHLA modulation in thymic maturation
Authors: Gambon Francisco , Kreisler Miguel , Díaz‐Espada Fernando
Published: March 2007

The correlated expression of several surface antigens (CD 1, class I HLA, CD 3) was examined in human unfractionated thymocytes or selected subsets by using single or double‐color flow cytometry. Prethymocyte subpopulations expressed high levels of HLA. A high proportion of cortical cells expressed low levels of either HLA or CD 3 antigens. Most of these HLA+ cortical cells corresponded to the more immature cells and did not express HLA‐B loci products. CD 1 a and CD 3 antigens were expressed in a high percentage of cells and the levels of expression of each antigen in individual cells were inversely correlated. These data and the contour of double‐color histograms are suggestive of the existence of a single pathway of thymocyte differentiation in which class I HLA expression is switched off around the time of the initiation of CD 3 (and Ti?) expression. We suggest that the anti‐major histocompatibility complex (MHC) specificity of the unselected Ti receptor may be incompatible with the expression of MHC products on the cell membrane. At this stage, CD1 antigens, whose expression is inversely correlated with that of HLA, may fulfill the role of MHC antigens. The latter can be re‐expressed later on, once the anti MHC specificities of the Ti receptors have been selected against. Studies on in vitro modulation of HLA molecules by interferon‐a did not reveal any correlation to the expression of CD 1 or CD 3 antigens.
Murine CD2 gene expression during fetal thymus ontogeny
Authors: Owen Michael J. , Jenklnson Eric J. , Brown Marion H. , Sewell William A. , Krissansen Geoffrey W. , Crumpton Michael J. , Owen John J. T.
Published: March 2007

The expression of the murine CD 2 gene and the interleukin 2 receptor IL2R has been investigated during fetal thymus ontogeny. CD2 mRNA was undetectable at embryonic day 14 but was readily detectable at day 15 of gestation. Surface IL2R expression was maximal at day 14 and was clearly detectable at day 13. These results indicate that IL2R expression precedes that of CD2 by at least 2 days.
Reactivity of Ly‐2+ T cells against 2,4,6‐trinitrophenyl (TNP)‐modified syngeneic stimulator cells: specificity, frequency of interleukin 2‐producing Ly‐2+ helper T cells and clonal segregation from Ly‐2+ cytotoxic T lymphocytes
Authors: Schmitt Joachim , Wagner Hermann , Heeg Klaus
Published: March 2007

The in vitro reactivity of purified murine Ly‐2+ and L3T4+ T cells towards 2,4,6‐trinitrophenyl (TNP)‐modified syngeneic stimulator cells was analyzed. Both T cell subpopulations autonomously proliferated and produced interleukin 2. In either the Ly‐2+ or L3T4+ T cell subset the frequencies of TNP‐specific interleukin 2 (IL 2)‐producing T lymphocyte precursors (IL 2 TL‐p) were equally high (f = 1/400–1/1000). Clonally developing IL 2 TL of either T cell subset showed an exquisite antigen (TNP) specificity as shown by the split culture approach. TNP‐specific Ly‐2+ IL‐2 TL used class I MHC (H‐2K ) gene products as major histocompatibility complex (MHC) restriction elements, while L3T4+ IL 2 TL proved to be class I1 MHC (H‐21‐Ak I‐Ek) restricted. Clonal segregation analyses revealed that the majority of clonally developing TNP‐reactive Ly‐2+ TL segregated into either IL 2 TL‐p or cytotoxic T lymphocyte presursors, i.e. both functions appear to be mutually exclusive. Less than 10% of the responding Ly‐2+ T cells seemed to be bifunctional. These findings provide compelling evidence for the L3T4+ T cell‐independent, autonomous reactivity of Ly‐2+ T cells in MHC‐restricted antigen‐specific responses and suggest T‐T cell interactions within the functional heterogenous Ly‐2+ T cell population.
Stimulation and proliferation of CD4+ peripheral blood T lymphocytes induced by an anti‐CD4 monoclonal antibody
Authors: Carrel Stefan , Moretta Alessandro , Pantaleo Giuseppe , Tambussi Giuseppe , Isler Patrick , Perussia Bice , Cerottini Jean‐Charles
Published: March 2007

There is experimental evidence that the CD4 molecule participates in the antigen‐driven activation of T cells expressing this surface glycoprotein. Whether CD4, a member of the immunoglobulin supergene family, acts as a ligand‐binding molecule and/or is directly involved in the activation pathway has yet to be established. In this study, we show that human CD4+ lymphocytes can be activated by exposure to the anti‐CD4 monoclonal antibody (mAb) B66. Normal peripheral blood CD4+ cells were induced to proliferate and to synthesize interleukin 2 (IL2) by the antibody. The specificity of the antibody stimulatory activity was tested by using IL2‐producing clones bearing either CD4 or CD8 on their surface. IL2 production was induced by mAb B66 in CD4+, but not CD8+, clones, whereas both types of clones responded to stimulation by the anti‐CD3 mAb Leu‐4. Despite its unique stimulatory activity, mAb B66 shared with other anti‐CD4 antibodies the ability to inhibit the specific cytolytic activity of CD4+ effector cells. These results clearly indicate that cross‐linking of surface CD4 molecules with appropriate antibodies can fully activate CD4+ lymphocytes. Whether the natural ligand for CD4 can trigger this activation pathway remains to be defined.
T cell recognition of endogenous IgG2a expressed in B lymphoma cells
Authors: Bikoff Elizabeth K. , Yu Hua , Eckhardt Laurel A.
Published: March 2007

We recently characterized a panel of C57BL/6J T cell clones specific for IgG2a of the a allotype in association with I‐Ab. Several of the clones gave surprisingly strong responses in the presence of normal spleen cells from several H‐2b strains, including C3H.SW, A.BY, D1.LP and BALB.B, without the addition of exogenous antigen. Experiments using Igh‐congenic mouse strains demonstrated that this response was directed towards shared allotypic determinants expressed on endogenously synthesized IgG2a molecules in various strains. Here we present evidence that the cell(s) responsible for this stimulation are conventional low density splenic accessory cells. Presentation of endogenously synthesized IgG2a by this population of dendritic cells, macrophages, and/or activated B cells was chloroquine sensitive. Thus, we conclude that this response is probably directed towards secreted IgG2a molecules that are internalized, processed and re‐expressed at the cell surface in association with class II molecules.

We also tested the ability of T cell clone B61‐34 to respond in the presence of the B lymphoma cell line M12.C3.A2. A strong response was again observed in the absence of exogenous antigen. Northern gel analysis of M12.C3.A2 messenger RNA provided evidence that these cells synthesize IgG2a in both a secreted and a membrane form. The response directed towards endogenous IgG2a expressed in M12.C3.A2 lymphoma cells is chloroquine resistant and considerably more efficient than that stimulated by IgG2a added as exogenous soluble antigen. These results demonstrate for the first time that B cells have the capacity to present antigenic determinants expressed on endogenously synthesized immunoglobulins to class II‐restricted T cells. The implications of these findings with respect to network models of immune regulation are discussed.
Soluble CD23 is released by B lymphocytes cycling in response to interleukin 4 and anti‐Bp50 (CDw40)
Authors: Cairns Jennifer , Flores‐Romo Leopoldo , Millsum Michelle J. , Guy Graeme R. , Gillis Steven , Ledbetter Jeffrey A. , Gordon John
Published: March 2007

An enzyme‐linked immunoassay was developed to quantitate the production of soluble CD23 from cycling B lymphocytes. This molecule has identity both with B cell‐derived B cell growth factor and with an IgE‐binding factor. B lymphocytes, which had been stimulated for 3 days with phorbol dibutyrate and calcium ionophore, washed and recultured, failed to produce detectable levels of CD23 over the following 3 days. Soluble CD23 was found, however, in the supernatant of cultures where recombinant interleukin 4 had been included. The level of CD23 rose dramatically when anti‐Bp50 had also been added. By contrast, anti‐Bp50, alone or together with low molecular weight T cell‐derived B cell growth factor, failed to promote the release of CD23 in detectable amounts. There was a strong correlation between the appearance of soluble CD23 in culture supernatants and the expression of CD23 on the surface of restimulated cells. The level of CD23 release appeared to relate more to the continued cycling of cells than to their differentiation to immunoglobulin secretion. These findings are discussed with particular emphasis on the role of CD23 as an important multi‐functional lymphokine in B lymphocyte physiology.
T helper cell‐dependent induction of resting B cell differentiation need not require cognate cell interactions
Authors: Julius Michael H. , Rammensee Hans‐Georg
Published: March 2007

We have analyzed the role of cognate interaction with helper T cells (Th) in support of resting B cell differentiation to plaque formation. Co‐culture of histoincompatible resting B cells and resting Th cells resulted in the induction of plaque‐forming cells when dimeric but not monomeric fragments of anti‐T cell receptor (TcR) antibody were added to culture. The efficiency of B cell activation was comparable to that supported by lipopolysaccharide and lectin‐mediated Th‐B cell conjugate formation. Further, if resting Th cells were preactivated with antigen and histocompatible antigen‐presenting cells, the requirement for addition of anti‐TcR to mixtures of histoincompatible Th and B cells was obviated. These results demonstrate that TcR‐mediated Th recognition of major histoincompatibility complex class II/antigen composites on the resting B cell membrane does not provide obligate signals for B cell differentiation to plaque formation. We are left with two possibilities. Either the entire process of Th cell‐dependent induction of resting B cell differentiation is mediated by soluble lymphokines or if Th‐B cell contact is mandatory, it is mediated through nonpolymorphic cell surface determinants.
Genetics and strain distribution of concanavalin A‐reactive Ly‐2‐, L3T4‐ peripheral precursors of autoreactive T cells
Authors: Morisset Jean , Trannoy Emanuelle , Talance Anne De , Spinella Sylviane , Debré Patrice , Godet Philippe , Seman Michel
Published: March 2007

Cytotoxic treatment of BALB/c cells from different peripheral lymphoid tissues by a cocktail of monoclonal antibodies against Thy‐1, Ly‐1, L3T4 and Ly‐2 differentiation markers (anti‐T cocktail) plus complement eliminates all mature T lymphocytes. Yet a population of dull Thy‐1+, Ly‐1‐, L3T4‐, Ly‐2‐, corresponding to about 1% of the initial population, can be detected by flow cytometry which proliferate under concanavalin A stimulation. These anti‐T killing‐resistant cells (TKR) were previously shown to be capable of differentiating in culture into class II‐restricted autoreactive T helper cells. We demonstrate here that such cells can be detected in mice of BALB/c and DBA/2 genetic background but are absent in C57BL/6 and B10 animals. The presence of TKR cells is dominant in (BALB/c X C57BL/6)F1 hybrids and genetically controlled by two genes which are neither H‐2 nor Igh linked. TKR cells are also detected in young NZB mice but disappear with the development of the systemic autoimmune disease in old animals. Thy‐1+, L3T4‐, Ly‐2‐ cells from MRL lpr/lpr mice also respond to concanavalin A but are removed by the anti‐T treatment. Altogether, arguments are presented suggesting that TKR cells represent a particular subset of double‐negative peripheral T cells which may correspond to autoreactive T cell precursors that would escape the thymic selection. We postulate that these cells are present in all mouse strains but their susceptibility to killing by anti‐Thy‐1 antibodies differs depending on background genes.
Analysis of CD3 and antigen receptor expression on T cell subpopulations of aged athymic mice
Authors: Lawetzky Alexandra , Hünig Thomas
Published: March 2007

The expression of the T cell antigen receptor on subpopulations of extrathymically generated T cells from athymic mice was investigated and compared to antigen receptor expression in normal mice. To this end, spleen and lymph node cells from 18 individual athymic BALB/c nu/nu mice between 6 and 12 months of age and from normal controls were enriched for T cells by nylon wool filtration. Expression of the following cell surface markers was analyzed by two‐color flow cytometry: Thy‐1, CD4, CD8, Vβ8 and CD3. The distribution of subpopulations as defined by these markers varied much more among athymic than among normal mice. Some recurrent patterns did, however, occur that may be characteristic of the extrathymic pathway of T cell differentiation in nu/nu mice.

Among Thy‐1.2+ cells, CD8+ cells predominated over CD4+ cells. No CD4+8+ “double positive” cells were found, but CD4‐8‐ “double negative” cells constituted 16% on average. All nu/nu nylon wool‐nonadherent cells expressing Thy‐1 at a normal level also expressed CD3, whereas Thy‐1low and Thy‐1‐ cells were CD3‐. The fraction of Vβ8 T cells among the CD4+ and CD8+ subsets was near to normal in the majority of these animals. Most interestingly, the density of Vβ8 and CD3 expression was lower in athymic than in euthymic animals. This level of T cell antigen receptor expression was, however, higher than on immature CD4+8+ thymocytes.

A fraction of the nude T cells presently characterized responded with proliferation to both anti‐T cell receptor Vβ8 monoclonal antibody and to concanavalin A. Despite their apparently normal phenotype (with the exception of reduced T cell receptor expression), this response was, however, 4 to 10 times smaller than that of normal control cells. The presently described Thy‐1+ T cell receptor intermediate cells may either be a(n) aberrant lineage(s) only generated extrathymically, or represent the accumulation of an immature intermediate stage of normal (i.e. thymic) T cell differentiation.
Growth‐dependent variation of major histocompatibility complex (MHC) restriction and expression of Ly‐2 and CD3/α/βT cell receptor in cloned cytotoxic T cells
Authors: Weltzien Hans Ulrich , Kempkes Bettina , Studer Roland , Melchers Inga , Eichmann Klaus
Published: March 2007

The specificity of major histocompatibility complex (MHC)‐restricted antigen recognition by cytotoxic T cells (CTL) has been clearly correlated to the α/β T cell receptor (TcR) complex on the T cell surface. Occasional changes in the specificity of in vitro cultivated CTL clones, therefore, have been suspected to result from alterations of the genes coding for the TcR α and/or β chain. Here we demonstrate that pronounced variations in the stringency of MHC restriction, previously reported to occur during long‐term culture of 2,4,6‐trinitrophenyl (TNP)‐specific CTL clones, may occur rapidly in a growth‐dependent, reversible manner, i.e. without structural TcR variation. Several H‐2b TNP‐specific CTL clones were shown to possess strong cross‐reactivity for H‐2b TNP target cells when seeded at low cell numbers, but exhibit reduced or undetectable cross‐reaction to H‐2k TNP in high‐density cultures. Another clone revealed “heteroclitic” properties with sinificantly stronger cytotoxic activity towards allogeneic (H‐2k) than syngeneic (H‐2b) TNP‐modified target cells. In this case dilute cultures appeared as exclusively allo‐MHC restricted, whereas dense cultures were allo/self cross‐restricted.

In all instances these phenomena were accompanied by cell density‐dependent quantitative changes in the expression of Ly‐2 and T cell antigen receptor. CTL from dilute cultures had at least 2‐fold higher surface concentrations of Ly‐2 and CD3 antigens than cells from dense cultures while other surface markers such as Thy‐1 or LFA‐1 were completely identical. No such effects were observed for CTL clones exhibiting cell density‐independent specificity patterns. We conclude from these findings that (a) the stringency of MHC restriction specificity may be significantly affected by the amount of expressed TcR and/or Ly‐2 molecules, (b) CTL possess mechanisms to regulate Ly‐2 and TcR expression and, hence, their MHC‐restricted antigen recognition, and (c) the ability to regulate Ly‐2 and TcR expression may be altered during prolonged culture of a CTL clone.