bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functional mosaicism of the lymphocyte plasma membrane. II. Characterization of membrane subtractions of activated thymocytes
Authors: Rode Harold N. , Mähler Bernd , Loracher Alois , Resch Klaus 
Published: February 2007

AbstractPlasma membranes of thymus lymphocytes can be fractionated by affinity chromatography on concanavalin A (Con A)‐Sepharose into two major fractions: one, MF‐1, elutes freely from the affinity column, the second, MF‐2, adheres specifically to Con A‐Sepharose. The adherent fraction MF‐2 carries mitogen receptors with higher affinity and is enriched in two enzymes, (K+ + Na+)‐ATPase and acyl‐CoA:lysolecithin acyltransferase (Resch, K. et al., Biochim. Biophys. Acta 1978. 511: 176). Microsomal membranes, derived more than 85% from the plasma membrane, of mitogen‐activated calf thymocytes were fractionated by affinity chromatography into similar fractions like resting lymphocytes, i.e. into MF‐1 and MF‐2. The activities of various membrane‐bound enzymes and fatty acid incorporation into these subfractions were compared to the corresponding similar subf ractions of nonactivated thymocytes. It appeared that two enzymes which were involved in lymphocyte activation, i.e. (K+ + Na+)‐ATPase and acyl‐CoA:lysolecithin acyltransferase, were enriched in the adherent fraction MF‐2 of microsomes from both normal and mitogen‐activated thymocytes and that both were activated primarily in this fraction. Adenylate cyclase was moderately enriched in the MF‐2, but was marginally activated in both fractions of membranes of mitogen‐activated cells. Alkaline p‐nitrophenyl phosphatase, Mg2+‐ATPase and γ‐glutamyltransferase were more or less evenly distributed in the plasma membrane and were strongly inhibited in both fractions of membranes from mitogen‐activated cells. Although acyl‐CoA:lysolecithin acyltransferase was activated preferentially in MF‐2, it was found that isotopically labeled fatty acids incorporated into the phospholipid lecithin quickly diffused throughout the whole membrane. These results suggest that specialized areas of the plasma membrane exist around the high‐affinity mitogen receptors which initially respond to the binding of mitogens.
Human T lymphocyte receptors for IgM: control by IgG‐binding lymphocytes
Authors: Samarnt Christiane , Revillard Jean‐Pierre 
Published: February 2007

AbstractThe capacity of human peripheral blood lymphocytes to bind antigen‐IgG or antigen‐IgM‐antibody complexes was investigated using a rosette technique with ox erythrocytes (E) coated with rabbit IgG (AG) or IgM (AM) antibodies. EAM rosette formation was achieved only in suspensions pre‐incubated for 24 h at 37°C. Addition of either EAM or EAG complexes to the culture medium was shown to prevent the formation of EAM rosettes. The inhibition was reversible, it was not due to trace IgM contaminants in the IgG antibody fraction. It was not observed when lymphocytes depleted of EAG‐rosetting cells were incubated with EAG complexes. Inhibition of the expression of lymphocyte receptors for IgM can be regarded as a consequence of the modulation of surface receptors for IgG and involves an interaction between the two lymphocyte subsets bearing surface receptors for IgG and IgM, respectively. However, these experiments do not exclude the possibility that a few cells which bind EAG may lose their receptors by modulation and then express a receptor for IgM.
Idiotypic cross‐reactivity of human and murine phosphorylcholine‐binding immunoglobulins
Authors: Riesen Walter F. 
Published: February 2007

AbstractThe idiotypic cross‐reactivity of mouse and human monoclonal immunoglobulins with binding activity for phosphorylcholine (PC) was investigated, using an idiotypic antibody elicited against the PC‐binding human IgMFR. The isolated FR heavy chain proved to be a better inhibitor for the reaction of IgMFR with anti‐FR than the FR light chain, but the intact protein was necessary for full idiotypic expression. PC was an inhibitor only at concentrations greater than 10−3 M indicating that the idiotypic antibody was not combining site‐directed. Among the murine PC‐binding IgA myeloma proteins, MOPC 167 was found to be the best inhibitor, but its inhibitory capacity was about 4 orders of magnitude lower than that of the homologous IgMFR. McPC 603 was an even weaker inhibitor, while TEPC 15 effected no better inhibition than human monoclonal immunoglobulins without PC‐binding activity. MOPC 167 has a most similar binding specificity to IgMFR as indicated by the high affinity for choline of these two proteins. TEPC 15 and McPC 603, on the other hand, exhibit a much lower affinity for choline. In addition to their similarity in specificity, proteins FR and MOPC 167 show important structural similarities within parts of their heavy and light chain variable domains. The data provide some evidence for the existence of idiotypic cross‐reactivity between the two species man and mouse.
Initiation of the blastogenic response of lymphocytes by hyperoptimal concentrations of concanavalin A
Authors: Steen Harald B. , Lindmo Tore 
Published: February 2007

AbstractThe blastogenic response of human lymphocytes in vitro to hyperoptimal concentrations of concanavalin A (Con A) has been studied by means of volume spectroscopy (measuring cellular and nuclear volume), flow cytofluorometry (measuring cellular DNA content) and incorporation of [3H]thymidine ([3H]dThd). The optimal Con A dose with respect to [3H]dThd incorporation was about 30 u, g/ml. In cultures given hyperoptimal doses, e.g. 100 μg/ml, [3H]dThd incorporation was strongly inhibited, whereas the number of cells entering S‐phase and significantly increasing their cellular and nuclear volume was considerably larger than with 30 μg/ml. With 200 μg/ml Con A, which induced negligible [3H]dThd incorporation, the percentage of responding cells was even larger. Hence, doses of Con A, which were hyperoptimal with regard to [3H]dThd incorporation, induced blastogenic response, including DNA synthesis, in a larger percentage of the cells than did the optimal dose. However, in cultures with hyperoptimal Con A doses, the progression of the cell cycle stagnated mainly during S‐ and G2‐phase and few cells completed mitosis. Thus, the blocking effect of hyperoptimal doses was not confined to any particular point of the cell cycle. The reduced [3H]dThd incorporation, seen with hyperoptimal doses, is attributed partly to a failure of this assay under such conditions.
Antigen‐specific helper T cells are essential for cytotoxic T cell responses to metabolically inactivated stimulator cells
Authors: Pilarski Linda M. 
Published: February 2007

AbstractPrimed spleen cells respond well to metabolically inactivated stimulator cells while normal spleen cells do not. This observation has been interpreted as showing that cytotoxic T cell precursors are different from unprimed precursors in their antigen recognition requirements for induction. A different model is proposed here which accounts for these observations as due to enhanced helper cell levels in primed populations. Experiments are described in this study which test several predictions of this model. These experiments show that in the presence of in vitro primed helper T cells, normal cells are able to respond efficiently to glutaraldehyde‐fixed stimulator cells. The helper effect is antigen‐specific. Since unprimed spleen cells can be efficiently induced by metabolically active stimulators (γ‐irradiated cells) and can respond to glutaraldehyde‐fixed antigen (metabolically inactive cells) only in the presence of specific helper cells, it seems reasonable to propose that helper cell signals are enhanced by a nonantigenic property of γ‐irradiated stimulator cells requiring metabolic activity. It is also clear that glutaraldehyde‐fixed cells are anti‐ genically intact as helper cells, primed to antigens on γ‐irradiated stimulator cells, efficiently and specifically help a response to fixed stimulators. Conversely, helper cells primed in vitro to glutaraldehyde‐fixed stimulators recognize antigen on γ‐irradiated stimulator cells. The level of help generated in response to glutaraldehyde‐ fixed stimulator cells is at least 10‐fold higher in primed cells than in normal cells. In addition, primed spleen cells can be induced in vitro to yield helper function by both fixed or unfixed stimulator cells. Normal helper cell precursors are induced at least 100‐fold more efficiently by γ‐irradiated as compared to glutaraldehyde‐fixed stimulator cells. This work supports the idea that a major effect of priming, which allows primed cells to respond to metabolically inactive stimulators, is to enhance levels of helper T cells in the primed population.
Occurrence of β2‐microglobulin in mammalian lymphocytes and erythrocytes
Authors: Björck Lars , Åkerström Bo , Berggård Ingemar 
Published: February 2007

AbstractCell‐associated β2‐microglobulin (β2m) has been studied by quantitative techniques in lymphocytes and erythrocytes of guinea pig, rabbit, rat and man. β2m was solubilized by sonication followed by treatment with acid, deoxycholate or thiocyanate, and then determined by radioimmunoassay. The average number of β2m molecules per lymphocyte, estimated after acidification, varied between 0.89 × 105 and 7.1 × 105. Rat erythrocytes contained 3.0 × 103 molecules per cell, whereas no β2m was detected in red blood cells from the three other species. A relatively large part of β2m in the mammalian lymphocytes and in rat erythrocytes was present on the cell surface according to a radioimmunoassay procedure using anti‐β2m antisera that had been absorbed with the blood cells analyzed.
Ontogeny of cells involved in the suppressor circuit of the immune response
Authors: Ptak Wlodzimierz , Naidorf Kenneth F. , Strzyzewska Jolanta , Gershon Richard K. 
Published: February 2007

AbstractSome macrophage (MΦ) cell surface structures which bind T cell‐derived factors remain intact after the MΦ are killed by heating at 56°C(but not 72°C) for 45 min. As a result, appropriately killed MΦ (HK MΦ) can act as competitive antagonists for those MΦ functions which are involved in binding and active presentation of T cell derived regulatory signals. By blocking the transmission of these signals with HK MΦ, we have found that the spleens of newborn mice contain considerable numbers of “latent” helper cells whose activity is not ordinarily seen because it is overridden by suppressor mechanisms. Similarities between these neonatal helper cells and a subset of adult T helper “inducer” cells (cell surface phenotype Ly‐1+; Ly‐2−,3−; IJ+; Qa l+), whose activity appears in significant numbers only after immunization, are described.
Serological analysis of antigen‐specific helper factors specific for poly‐L(Tyr, Glu)‐poly‐DLAla–poly‐LLys [(T, G)‐A–L] and LGlu60‐LAla30‐LTyr10 (GAT)
Authors: Howie Sarah , Parish Chris R. , David Chella S. , McKenzie Ian F. C. , Maurer Paul H. , Feldmann Marc 
Published: February 2007

AbstractIn vitro prepared antigen‐specific helper factors reactive to the synthetic polypeptide antigens poly‐L(Tyr, Glu)‐poly‐DLAla‐ ‐poly‐LLys [(T, G)‐A‐ ‐L] or LGlu60‐La30‐ LTyr10 (GAT) and bearing Ia determinants were analyzed serologically to determine the nature of the Ia determinants they expressed.I subregion‐specific mouse anti‐Ia antisera were used, and showed that (T, G)‐A–L specific helper factor (HF) contains I‐A subregion‐controlled determinants, whereas GAT‐specific HF carries I‐J subregion‐controlled antigens. This unexpected finding was confirmed in both the H‐2k and H‐2b haplotypes, using a variety of anti‐I‐J antisera.Rabbit anti‐Ia antisera also reacted with both HF which raised the possibility that the Ia determinants on HF may be carbohydrate in nature. The fact that HF has a low molecular weight and yet contains Ia determinants, antigen‐binding capacity and idiotypic markers is compatible with this interpretation.
Biphasic rate of synthesis of glycoconjugates, phospholipids and DNA in concanavalin A‐stimulated mouse thymocytes. Involvement of cortisone‐sensitive and ‐resistant subpopulations
Authors: van Eijk Ronald V. W. , Mühlradt Peter F. 
Published: February 2007

AbstractThe time course of the rate of labeling of membrane components (phospholipids, glycolipids and glycoproteins) and DNA was followed in concanavalin A‐stimulated CBA/J mouse thymocyte cultures. Two peaks of stimulated biosynthetic activity were noted, the first at the beginning of the cultivation and the second about 25 h later. Both early and late peaks of biosynthesis of membrane components were accompanied by blast transformation and were unimpeded by suppression of DNA synthesis by hydroxyurea.Cortisone‐sensitive and cortisone‐resistant thymocytes were prepared by selective agglutination of the cortisone‐sensitive cells with peanut agglutinin (Reisner et al. Cell. Immunol. 1976. 25: 129) or cortisone treatment of the animals. Cortisone‐sensitive cells responded early, while the cortisone‐resistant population gave only the late response.The autoradiographic patterns from sodium dodeeyl sulfate polyacrylamide gels of [3H]fucose or [3H]galactose‐labeled glycoproteins from early and late labeling cells, and cortisone‐resistant cells, were compared. Late‐labeling and cortisone‐resistant cells gave indistinguishable patterns, but differed significantly in their patterns from early‐labeling cells.It is concluded that the two peaks of biosynthetic activity during the course of concanavalin A stimulation of thymocytes are caused by two different cell populations which require different times for maximal response and react independently of one another.
Mutations affecting immunoglobulin light chain secretion by myeloma cells I. Functional analysis by cell fusion
Authors: Mosmann Timothy R. , Baumal Reuben , Williamson Alan R. 
Published: February 2007

AbstractTwo clones of MOPC 315 cells have been selected which synthesize but do not secrete Ig lambda light chains. These clones were analyzed by fusion with a cell line synthesizing and secreting kappa chains. Conditions were established for recovery at high frequency (approximately 10−3) of spontaneously fused, viable hybrid cells. The resulting hybrid cell lines synthesized both kappa and lambda chains but secreted only kappa chains. Hybrid cells produced by fusion of a lambda‐secreting clone of MOPC 315 with the kappa‐secreting cell line were also isolated and shown to synthesize and secrete both kappa and lambda chains. These results suggest that the nonsecretion of lambda chains was not due to a defect in the secretion mechanism of the variant cells. A more likely alternative is that the lambda chains in the variant cell lines were structurally altered to a form which could not be secreted.
Inhibition of killer‐target cell interaction by monoclonal anti‐H‐2 antibodies
Authors: Lindahl Kirsten Fischer , Lemke Hilmar 
Published: February 2007

AbstractThe sites on target cells with which cytotoxic T lymphocytes interact were characterized using three different monoclonal BALB/c anti‐CBA antibodies derived from plasma cell hybrids. The antibodies all reacted with H‐2Kk and appeared to recognize public specificities H‐2.5,11 and 25, respectively. Allogeneic killing directed at products of H‐2Kk was inhibited by all three antibodies, irrespective of the H‐2 haplotype of the responder; cytotoxicity directed at products of another allele, H‐2Kd, or of the H‐2 D region on the same target cell was not affected. The antibodies did not inhibit killer cells carrying H‐2Kk. Cytotoxic reactions against minor histocompatibility antigens, including the male‐specific antigen H‐Y, were also blocked by all three monoclonal antibodies when restricted by H‐2Kk, but not when restricted by H‐2D on the same target cell. Cytotoxic T lymphocytes thus appear to interact with their target via the same, serologically defined H‐2Kk molecule which carries public specificities, whether they recognize it as an alloantigen or as self. This argues against the existence of separate H‐2 K‐encoded molecules recognized by killer cells only and against H‐2 specific modifications of minor histocompatibility antigens as the basis of H‐2 restriction.One of the antibodies, 27 R9, which reacted with H‐2Kk and H‐2′ and was thought to recognize specificity H‐2.25, showed a weak cytotoxic reaction but bound with a high titer to H‐2 Dk, a reaction that has not previously been described. This antibody selectively and with a very high titer inhibited male‐specific cytotoxicity restricted by H‐2Dk, but did not significantly interfere with allogeneic killing against products of the H‐2 Dk region nor apparently with H‐2Dk‐ restricted cytotoxicity specific for other minor antigens. The results suggest the existence of at least two different restriction elements controlled by the H‐2Dk region.
The specificity of nonspecific concanavalin A‐induced helper factors
Authors: Bemabé Rosa R. , Martinez‐Alonso Carlos , Coutinho Antonio 
Published: February 2007

AbstractAddition of supernatants from concanavalin A (Con A)‐stimulated spleen cells enable nude spleen cells to respond in vitro to a variety of antigens (in our experiments, sheep (SRBC) and horse erythrocytes (HRBC)). Experiments presented here, indicate that such nonspecific helper supernatants are in fact a polyclonal mixture of diverse, specif‐ ic activities. Con A stimulation of thoracic duct lymphocytes, specifically depleted of SRBC or HRBC‐reactive cells by the Sprent technique, results in a specific decrease in the activity to the relevant antigen. On the one hand, Con A stimulation of in vivo activated thymocytes results in the production of helper supernatants which are almost totally specific for the antigen used in priming.In spite of these indications of specificity, it has been impossible to absorb out helper activity from normal Con A supernatants on the corresponding antigen. Specific removal of helper activity, however, can readily be achieved by absorbing helper supernatants on complexes of antigen and early immune sera. Various control ex‐ periments demonstrate that the loss of activity in the absorbed supernatants is not due to carry‐over of antibody into the test cultures. Furthermore, the fraction of helper activity that can be specifically removed on antigen‐antibody complexes depends on the conditions used in the preparation of the supernatants; this fraction is highest when Con A activation of T cells is performed in the presence of B cells without antigen.These results suggest that “nonspecific helper factors” are a mixture of diverse molecules, some of which show specificity for variable regions of antibodies.
In vitro evidence from anti‐hapten antibody responses for T helper and suppressor cells directed against major histocompatibility antigens in the mouse. Participation of I region determinants in the induction of T helper cells
Authors: Vogt Peter , Simpson Elizabeth 
Published: February 2007

AbstractThe antibody response to murine alloantigens is thought to be thymus‐dependent. In this study, we were using H‐2 and H‐minor antigens presented on the surface of cells as particulate carriers and 2, 4, 6‐trinitrophenyl (TNP) as a hapten.To study conditions for the induction of T helper and T suppressor cells directed against such antigens, T cell donor mice of a given inbred strain were primed with spleen cells of another inbred strain differing in distinct subregions of its H‐2 haplotype and/or differing in its H‐minor haplotype. Spleen T cells of mice in vivo allogeneically (carrier)‐primed in this way were cocultured in vitro with splenic in vivo TNP (hapten)‐primed B cells plus irradiated TNP‐conjugated spleen cells (hapten‐carrier conjugate) from the haplotype used for carrier priming.The anti‐hapten antibody response was taken as a quantitative indicator of helper activity. Suppression was tested by measuring the reduction of the antibody‐forming cell response of in vivo TNP or sheep red blood cell (SRBC)‐primed B cells restimulated in vitro with homologous antigen in the presence of allogeneically primed T cells.Helper cell functions were clearly demonstrated when donors of T cells were primed to Ia antigens. Additional priming to K and/or D antigens yielded help and suppres‐ sion simultaneously, priming to K and/or D antigens alone and in some cases to H‐ minor antigens yielded no help but resulted in strong suppression. The effect of the helper cells was shown to be camer‐specific occurring only in the presence of the relevant carrier, whereas the suppressor T cells were of the nonspecific type sup‐ pressing both anti‐TNP and anti‐SRBC responses in the absence of any restimulating carrier. The helper effect was seen not only when the hapten was conjugated to the appropriate (allogeneic) cells but also when it was presented on an unrelated carrier (syngeneic cells) provided that the specific nonhaptenated carrier was present. ‐ Pos‐ sible recognition mechanisms are discussed.
Studies on T lymphocyte activation I. Requirements for the mitogen‐dependent production of T cell growth factors
Authors: Andersson Jan , Grönvik Kjell‐Olov , Larsson Eva‐Lotta , Coutinho Antonio 
Published: February 2007

AbstractConditioned media (CM) obtained from concanavalin A (Con A)‐stimulated spleen cell cultures maintain mitogen‐derived T cell blasts in exponential growth for indefinite periods of time. Such purified T cell blasts do not respond to Con A, and the growth‐promoting activity in CM is independent of the mitogenic lectin used for its production. However, the appearance of activity in CM is Con A dose‐dependent. Furthermore, the production of these T cell growth factors is independent of B cells, while it requires both T cells and nontheta‐bearing, probably la‐positive cells present in normal and nude spleens. On the other hand, the T cell blasts which are reactive to the growth factors, neither produce CM by themselves nor can they cooperate with nude spleen cells for its production, in the presence of a mitogenic lectin.Since the concentration of growth factors in CM determines the extent of T cell growth, we propose that the growth of some T cells is necessarily dependent upon the activity in CM described here and, consequently, that the basis for T cell activation is the induction of such growth factors.
Fine specificity of a continuously growing killer cell clone specific for H‐Y antigen
Authors: von Boehmer Harald , Hengartner Hans , Nabholz Markus , Lernhardt Waldemar , Schreier Max H. , Haas Werner 
Published: February 2007

AbstractH‐Y‐specific cytotoxic T cells were first cloned in soft agar and grown over a period of 8 months in media conditioned with supernatants from mouse and rat spleen cells stimulated with concanavalin A. The specificity of cloned cells and their cytolytic potential remained essentially unchanged over the entire culture period. In addition to lysing male target cells expressing H‐2 Db antigens, the cytolytic cells lysed also male as well as female cells expressing H‐2 Dd alloantigens. Seventeen out of eighteen subclones derived from the original clone revealed the same activity. The cells divide about every 17–20 h and can be obtained in large quantities.