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Biomedical subjects

E M Shevach

Publications and source records attributed to E M Shevach.

At least 181 records · Page 10Linked to original sources
PubMed1981

Alloreactive T cells from individual soft agar colonies specific for guinea pig Ia antigens. I. Production and initial characterization.

Allo-reactive T cells reactive with Ia antigens from strain 2 and 13 guinea pigs were cloned by plating T cells from primary mixed leukocyte cultures in soft agar and expanding the resulting colonies in liquid culture. Optimal expansion of the cultures from an individual colony was achieved by repeated stimulation with allogeneic cells in conditioned media. Mapping studies using stimulator cells from inbred and outbred guinea pigs and blocking studies with alloantisera and xenogeneic monoclonal antibodies to guinea pig Ia antigens indicated that these T cell colonies were specifically stimulated to proliferate by Ia molecules. In addition, these xenogeneic monoclonal anti-Ia antibodies had selective and differential inhibitory effects on the proliferative response of these alloreactive colonies. This result suggested that each T cell colony is specific for a distinct epitope expressed on Ia molecules. Furthermore, unlike heterogeneous cell populations in guinea pig primary and secondary mixed leukocyte cultures, most alloreactive T cell colonies expressed significant cytotoxic T lymphocyte activity that was also specific for Ia. Thus, the same cell proliferating to Ia is also a T killer cell. These T cell colonies will be useful for further analysis of the specificity and functional significance of the T cells responding in the mixed leukocyte reaction.

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PubMed1981

Characterization of an antiserum to guinea pig antithrombin III (AT III). I. Reactivity with guinea pig T lymphocytes.

In the course of studies investigating the effects of antisera prepared against a variety of guinea pig proteins on lymphocyte function, a goat antiserum prepared against a guinea pig gamma-globulin preparation was found to react with guinea pig T lymphocytes. This antiserum, serum 592, contained a significant titer of antibodies that were cytotoxic for a subpopulation of lymph node cells and thymocytes, and mitogenic for lymph node T cells. Immunoelectrophoretic analysis and selective absorptions of the antiserum demonstrated that the antigen recognized on thymocytes was also present on an alpha 2 globulin in guinea pig plasma, which, on the basis of physiochemical characteristics and heparin-binding affinity, appeared to be guinea pig antithrombin III (AT III). Although the antiserum was shown to contain antibodies to both protein and carbohydrate determinants on the AT III molecule, studies comparing the effects of 7 M guanidine and periodate oxidation on the antigenicity of the AT III determinant also recognized on the thymocytes indicated that this shared antigenic determinant was carbohydrate in nature. The thymocyte membrane molecule bearing this determinant was also isolated and was found to be a 210,000-dalton macromolecule that was very sensitive to proteolytic and/or autolytic degradation. These data raise the interesting possibility that guinea pig lymphoid cells may have a membrane-associated protease inhibitor related to plasma AT III.

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PubMed1981

Characterization of an antiserum to guinea pig antithrombin III (AT III). II. Stimulation of T lymphocyte proliferation.

A goat antibody specific for an antigenic determinant shared between guinea pig antithrombin III (AT III) and thymocytes was shown to be mitogenic for lymph node T lymphocytes in the presence of macrophages. Although the antiserum was not mitogenic for purified populations of B lymphocytes, B lymphocytes were as efficient as T lymphocytes in absorbing the mitogenic activity of the serum. The shared antigenic determinant appeared to be carbohydrate in nature in that native and guanidine-treated AT III, but not periodate oxidized AT III, were capable of inhibiting the mitogenic activity of the serum when added continuously to the cultures. The possibility that the plasma protease inhibitor AT III or an antigenically related membrane protein are involved in the regulation of T cell activation is discussed.

Absorption↗
PubMed1981

Alloreactive T cells from individual soft agar colonies specific for guinea pig Ia antigens. II. Cellular and molecular requirements for optimal proliferative responses.

We have investigated the cellular and molecular requirement for optimal proliferative responses of several alloreactive T cell lines that were derived from individual soft agar colonies and were specific for guinea pig Ia antigens. Optimal proliferation of several colonies was observed in cultures containing purified allogeneic macrophages and growth factor(s) present in supernatant fluids of Con A-activated T cells (Con A-S). Significant proliferative responses of these alloreactive T cell colonies were also routinely detected in cultures only supplemented with unfractionated irradiated allogeneic peritoneal exudate cell (PEC). The T cell component of the stimulator cell population was crucial for these responses by producing necessary growth factor(s) endogenously in the culture. Thus, 2 signals, allogeneic Ia antigens and growth factor(s), were required for optimal proliferative responses of these alloreactive T cell colonies. Furthermore, macrophage-associated Ia antigen was more efficient than B cell-associated Ia for these responses. The requirement for allogeneic Ia antigen was not absolute, since the colonies could easily be expanded when the cultures were supplemented with irradiated syngeneic PEC and the T cell mitogens, Con A or PHA. The effect of the mitogen was mediated via the T cells in the irradiated PEC, since removal of the T cells from these PEC markedly reduced the responses. Thus, it is likely that a nonspecific signal(s) presumably from T cells can promote proliferation of alloreactive T cell colonies in the absence of allogeneic Ia antigen. These results suggest 2 mechanisms of activation of these alloreactive T cells.

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PubMed1981

The syngeneic mixed leukocyte reaction represents polyclonal activation of antigen-specific T lymphocytes with receptors for self-Ia antigens.

We used a combination of positive and negative selection techniques to evaluate the relationship between the T cell that responds to self-Ia antigens in the SMLR and the T cells that respond to foreign antigen in association with self-Ia. BudR and light treatment of T cells proliferating in the SMLR abolished their subsequent primary and secondary proliferative response to antigen but had little effect on their response to allogeneic Ia. F1 cells that had been positively selected in the SMLR with stimulator cells from 1 parental strain demonstrated a markedly enhanced proliferative response to antigen in association with the parental strain used in the SMLR selection culture. The observed genetic restriction on the antigen responses of SMLR primed F1 T cells was not the result of haplotype-specific help or suppression and most likely represents direct activation of antigen-specific T cell clones by unmodified Ia antigens.

Animals↗
PubMed1981

Monoclonal antibodies to guinea pig Ia antigens. I. Production, serologic, and immunochemical characterization.

Xenogeneic antibodies to guinea pig Ia antigens were produced by application of the hybridoma technique. BALB/c mice were immunized with the Ia-positive B cell leukemia line EN-L2C of strain 2 guinea pigs, and the spleen cells were fused to the mouse myeloma line NS-1. Culture supernatants of hybrids growing in the selective HAT medium were screened in a binding assay, and hybrids selectively reactive with EN-L2C but not with its Ia-negative variant BZ-L2C were cloned. Ascitic fluid was produced and used as a source of antibody. Four independently derived antibodies proved to be specific for Ia antigens. Two of the antibodies (25E3 and 25E11) seemed to recognize alloantigenic determinants on strain 2 Ia antigens in that they bound only to the cells of strain 2 but not to the cells of strain 13 animals. Two other antibodies (22C4 and 27E7) were found to react with both strain 2 and strain 13 cells, and immunoprecipitation experiments revealed that these antibodies were directed to common determinants shared between certain strain 2 and strain 13 Ia antigens. All antibodies were cytotoxic in the presence of complement for EN-L2C (but not for BZ-L2C) leukemia cells and for lymph node, spleen, peritoneal exudate cells, thymocytes, and purified T cells of strain 2 guinea pigs. In addition, 22C4 was cytolytic for cells of both strains. These results indicate that antibodies can be obtained through the hybridoma technique that are able to distinguish different determinants on Ia antigen molecules of te guinea pig. These antibodies should provide a useful tool for further study of the role of Ia antigens in cellular interaction and Ia-Ir gene function.

Animals↗
PubMed1980

Monoclonal antibodies to guinea pig Ia antigens. II. Effect on alloantigen-, antigen-, and mitogen-induced T lymphocyte proliferation in vitro.

Four xenographic monoclonal antibodies to guinea pig Ia antigens were tested for their inhibitory effects on antigen-, alloantigen-, and mitogen-induced T cell proliferation. All four monoclonal antibodies reacted with strain 2 Ia antigens, and all four were capable of inhibiting the strain 13 against strain 2 mixed leukocyte reaction (MLR) by 50-70%; the two monoclonals that reacted with strain 13 Ia antigens were also capable of inhibiting the strain 2 against strain 13 MLR. In contrast, an analysis of the effects of a single monoclonal antibody on the responses to several antigens demonstrated a selective monoclonal pattern of inhibition in that the responses to some, but not all, antigens were inhibited. These results suggest that monoclonal antibodies react with different parts of Ia molecules that may have different functional roles and that certain parts of an Ia molecule participate in the presentation of certain antigens, whereas other regions of the same molecule present different antigens.

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PubMed1980

Antigen presentation and allogeneic stimulation by Langerhans cells.

Isolated Langerhans cells were studied for 2 immunologic functions, the ability to present antigen to sensitized T lymphocytes and the ability to act as stimulator cells for mixed lymphocyte reactions. Langerhans cells can perform both of these functions. This fact, with the previous finding that Langerhans cells possess surface Ia antigens and Fc and C3 receptors, strongly suggests that Langerhans cells act as epidermal macrophages.

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PubMed1980

The role of the major histocompatibility complex in the regulation of macrophage-T lymphocyte interaction.

The proliferative response of guinea pig T lymphocytes which have been primed in vivo can only be induced by antigen-pulsed syngeneic macrophages. The development of techniques to prime T lymphocytes in vitro has allowed us to demonstrate that the genetic restriction on the interaction of the macrophage and T lymphocyte is regulated by the Ia antigens of the macrophage used during the initial sensitization step. Following removal of alloreactive cells, T cells can be sensitized to antigen-treated allogeneic macrophages. It thus appears likely that T cells do not recognize antigen per se, but can only be sensitized to antigen-modified membrane components or to complexes of antigen combined with certain membrane molecules. We postulate that the Ia antigens themselves are the products of the immune response genes and function in both macrophages and B lymphocytes as antigen recognition structures.

Animals↗
PubMed1980

The functional role of Langerhans cells.

Langerhans cells represent a subpopulation of mammalian epidermal cells. The recent findings that these cells are the only epidermal cells which express Fc-IgG receptors, C3 receptors and Ia antigens support the early suggestion that they are related to cells from the monocyte-macrophage-histiocyte series. In this report, evidence is presented that epidermal Langerhans cell can replace Ia-bearing macrophages in their capacity to induce antigen-specific and allogeneic T cell activation. The possible clinical implications of these findings are discussed with regard to the role of Langerhans cells as sensitizing factors in contact hypersensitivity and skin graft rejection.

Animals↗
PubMed1980

The guinea-pig I-region. III. Distribution of Ia antigens in inbred and partially inbred strains.

We have used a combined serologic and structural approach to study the distribution of I-region associated (Ia) antigens in nine strains of inbred and partially inbred guinea-pigs. All of the inbred strains studied with the exception of strain 2 animals were found to share one or more I-subregions with inbred strain 13 animals. The BIOAD, R9, OM3, and BIOAC strains have the same I-region as strain 13 animals; the B/Lac strain has two subregions in common with strain 13, while the BIOB strain has a single subregion in common with strain 13. The availability of a number of different guinea-pig strains with well-characterized major histocompatibility complexes should facilitate the continuing use of this species in studies of immunogenetics, transplantation, and tumour immunology.

Animals↗
PubMed1980

The syngeneic mixed leukocyte reaction: the genetic requirements for the recognition of self resemble the requirements for the recognition of antigen in association with self.

We have used cells from inbred strain 2 and strain 13 guinea pigs in order to define further the role of Ia antigens in the syngeneic mixed leukocyte reaction (MLR). The guinea pig syngeneic MLR resembled the autologous MLR in man in that it demonstrated both memory and specificity. The Ia antigens appeared to be the proliferative stimuli in that the primary stimulator cell was an Ia-positive adherent peritoneal exudate cell (PEC) and the reaction could be specifically inhibited by anti-Ia sera directed to the stimulator cell. We also demonstrated the existence of two (2 x 13)F1 T cell populations that were capable of reacting to one or the other parental PEC in the absence of any known exogenous antigen. These results suggest that the syngeneic MLR may represent T cell activation mediated through a receptor for self Ia.

Animals↗
PubMed1980

Immunologic characterization of a granulocytic leukemia of inbred strain 13 guinea pigs: presence of Ia-positive myeloblasts.

Membrane markers expressed by a transplantable granulocytic leukemia induced in inbred strain 13 guinea pigs by N-nitroso-N-butylurea have been investigated by serologic and immunochemical methods. Although the leukemic myeloblasts have no detectable surface immunoglobulin or Fc receptors, they have been found to synthesize and express membrane antigens encoded for by the I-region of the major histocompatibility complex. Despite the presence of Ia antigens, these cells do not stimulate allogeneic T lymphocytes in the mixed lymphocyte reaction nor are they able to present soluble antigen to immune T cells. The presence of Ia antigens on immature myeloid cells suggests that these proteins may be important in cellular functions beyond those identified in the cellular immune system.

Animals↗
PubMed1980

TNP-coupled membranes stimulate T cell proliferation via the macrophage.

TNP-coupled membranes derived from guinea pig m phi were capable of inducing both primary and secondary antigen-specific T cell proliferative responses; however, effective stimulation by hapten-coupled membranes required the presence of unmodified m phi. A genetic analysis demonstrated that the Ia antigens of the unmodified m phi rather than the Ia antigens borne on the TNP-coupled membranes determined the histocompatibility restrictions on m phi T cell interaction.

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