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Results for “CD3 Complex”

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PubMed1989

Increased cyclic AMP levels block interleukin 2-induced protein kinase C substrate phosphorylation but not the mitogenic response.

Protein kinase C (PKC) has been implicated in the signaling of a number of cellular responses including activation of T cells. In the present report we have evaluated the effect of increased cAMP levels on PKC activation after stimulation of two distinct receptor systems on normal human T cells. PKC substrate phosphorylation can be induced via either the CD3 complex or, to a limited extent, the high affinity interleukin 2 (IL 2) receptor. Substrate phosphorylation via both pathways is shown to be blocked by increased intracellular levels of cAMP. In accordance with previous reports, the CD3-dependent autocrine proliferative response could also be blocked by a cAMP-dependent mechanism. Since direct activation of PKC with a phorbol ester reversed this inhibition, a causal relationship between cAMP-dependent PKC blockage and inhibition of the CD3 response is suggested. In contrast, however, initiation of IL 2-induced proliferation was essentially unaltered by cAMP and could progress in the apparent absence of PKC activity. Thus, this study indicates that IL 2-induced proliferation can under such conditions be completely uncoupled from IL 2-induced PKC activation in normal T cells.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1995

Selection of peripheral and intestinal T lymphocytes lacking CD3 zeta.

The CD3 zeta chain of the TCR plays a pivotal role in the activation of T cell responses toward foreign antigen and in the selection of the T cell repertoire. T lymphocytes from mice deficient in CD3 zeta (CD3 zeta/eta-/- mice) express very few cell surface TCR-CD3 complexes, and these animals have poorly developed thymuses which lack single-positive CD8 and CD4 thymocytes. Nevertheless, a substantial number of single-positive CD4+ and CD8+ T lymphocytes are found in peripheral lymphoid organs of CD3 zeta/eta-/- animals. Using double-mutant mice, generated by breeding CD3 zeta/eta-/- mice with others deficient in the expression of either class I or class II MHC molecules, we demonstrate here that positive selection of peripheral CD4+ and CD8+ T lymphocytes can occur in the absence of CD3 zeta/eta molecules. Analysis of the intestinal intra-epithelial lymphocytes from CD3 zeta/eta-/- mice revealed a novel T cell population expressing high levels of an alternative TCR alpha beta, due to the replacement of CD3 zeta by Fc epsilon RI gamma. Developmentally, these cells also depend on class I MHC expression. In contrast, TCR gamma delta/Fc epsilon RI gamma+ T cells develop independently of MHC class I or class II molecules. These experiments demonstrate that the unique subset of intestinal TCR alpha beta/Fc epsilon RI gamma+ lymphocytes is developmentally dependent on MHC expression. The restricted expression of TCR alpha beta/Fc epsilon RI gamma+ cells in the intestinal mucosa (rather than the thymus or lymph nodes) supports the hypothesis that selection of these T cells occurs extrathymically.

Animals↗

PubMed1991

Enhanced CD3-mediated T lymphocyte proliferation in patients with systemic lupus erythematosus.

Nonfractionated peripheral blood lymphocytes from patients with systemic lupus erythematosus (SLE) showed enhanced proliferative responses when stimulated via the CD3 pathway. In contrast, proliferative responses induced by phytohemagglutinin were diminished in SLE patients. Levels of CD3-induced interleukin-2 production and interleukin-2 receptor expression were comparable with normal levels. Highly purified T cells also showed augmented CD3 responses, but only in the presence of phorbol myristate acetate or a combination of phorbol myristate acetate plus calcium ionophore A23187, and not with calcium ionophore alone. The data suggest integrity of the T cell receptor/CD3 pathway for T cell activation in patients with SLE, as examined in cultures stimulated with specific anti-CD3 monoclonal antibodies rather than with multivalent lectins. An increased response via the CD3 complex could contribute to the autoimmune activity in human SLE.

Adolescent↗

PubMed1988

HIV-1-infected T cells show a selective signaling defect after perturbation of CD3/antigen receptor.

The binding of antigen or monoclonal antibody to the T cell receptor for antigen or the closely associated CD3 complex causes increases in the concentration of intracellular ionized calcium and subsequent cell proliferation. By measuring second messenger production in primary cultures of human immunodeficiency virus (HIV-1)--infected T cells stimulated with monoclonal antibodies specific for either CD3 or CD2, a specific impairment of membrane signaling was revealed. The HIV-1--infected T cells were unable to mobilize Ca2+ after stimulation with anti-CD3, whereas CD2-induced calcium mobilization remained intact. Furthermore, the HIV-1--infected cells proliferated poorly after CD3 stimulation, although the cells retained normal DNA synthesis in response to interleukin-2 stimulation. These results show that the signals initiated by CD2 and CD3 can be regulated independently within the same T cell; uncoupling of signal transduction after antigen-specific stimulation provides a biochemical mechanism to explain, in part, the profound immunodeficiency of patients with HIV-1 infection.

Acquired Immunodeficiency Syndrome↗

PubMed1991

Analysis of protein phosphorylation patterns reveals unanticipated complexity in T lymphocyte activation pathways.

Protein kinases are considered likely to play important roles in the still dimly understood process by which mitogens induce resting T lymphocytes to enter the cell cycle. Using two-dimensional electrophoretic analysis of lysates from orthophosphate-labeled cells, we have compared patterns of phosphorylation in freshly isolated murine splenic T cells exposed to three mitogenic agents: antibody to the epsilon-chain of the TCR CD3 complex, the plant lectin Con A, and a mixture of PMA and ionomycin, which together bypass the signal transduction apparatus to activate intracellular pathways. Of 14 phosphoproteins found whose level of phosphorylation was increased (at least fivefold) by anti-CD3 epsilon antibody, 13 also responded to the mixture of PMA and ionomycin. Surprisingly, however, only 5 of these 14 also responded strongly to Con A exposure. We also identified two substrates that were phosphorylated in response to Con A but not to anti-CD3. Phosphorylation patterns were also studied in T cells exposed to either PMA or ionomycin alone, to gain further insight into the role of protein kinase C and calcium-dependent events in the activation process. Of 16 phosphoproteins that responded to mixtures of PMA and ionomycin, 4 were shown to require the ionomycin signal, 2 to require the PMA signal, and 3 others to respond only when both activators were present; the other 7 responded to either agonist added alone. In addition, we found two PMA-sensitive phosphoproteins in which phosphorylation was inhibited by ionomycin induced calcium signals. Finally, we identified several phosphoproteins which show differential responsiveness in CD4+ and CD8+ T cells. Classification of kinase substrates based on their differential susceptibility to these stimuli should provide new insights into the mode of action of agents and diseases that affect T cell activation.

Adenosine Triphosphate↗

PubMed1990

OKT3 induction via idiotypic networks of mirror-image immunosuppressive antiimmunoglobulins in renal transplant recipients.

Four of 21 renal transplant recipients treated with OKT3 for rejection episodes developed a second sustained (approximately 2 weeks) depression in CD3 peripheral blood lymphocyte cell-surface-marker expression. This occurred after OKT3 therapy had ceased, subsequent to a return toward baseline CD3 levels seen before OKT3 therapy was instituted. The second decrease in CD3 T cell counts was dissociated from CD2 marker T cell counts using flow cytometry and coincided with transient cytomegaloviral infections. Three phases of immunosuppression were defined in these 4 patients: phase I (during OKT3 treatment); phase II (after treatment when CD3 counts were reconstituted); and phase III (when CD3 counts again were depressed). During phase III, serum of the 4 affected patients could transfer a blocking effect on the expression of the CD3 marker of peripheral blood T cells of "normal" laboratory volunteers. Contained in these sera were human IgG antibodies that bound on Western blot analysis and by radioautography after immunoprecipitation to a protein band of a T cell membrane lysate with an m.w. of 23 kD. The reaction was identical to that seen with OKT3 (immunoprecipitation). Moreover, this Western blot binding could be virtually (but not completely) eliminated by multiple absorptions of the T cell membrane lysate with OKT3. By using an affinity-purified human anti-OKT3 IgG from one of the 4 patients, it was possible to immunoabsorb from phase III sera the CD3 blocking activity as well as the binding to the 23 KD protein band. A reverse immune absorption by the phase III sera with the anti-OKT3 IgG after ultracentrifugation prevented the anti-OKT3 IgG from binding to OKT3 coated plates in solid-phase radioimmunoassay. These data support the notion that autoimmune human anti-anti-id (Ab2) antibodies can occasionally be generated by treatment with OKT3, which are directed against CD3 complex epitopes similar to the ligand of OKT3.

Adolescent↗

PubMed1989

Selective induction of growth factor production and growth factor receptor expression by different signals to a single T cell.

Stimulation of lymphokine production and the expression of receptors for growth factors can be dissociated in AK-8, a line of CD4+, I-A-restricted, conalbumin-specific mouse T cells. When activated by antibodies specific for the T cell receptor (TcR; F23.1) or the CD3 complex (145-2C11) adsorbed to plastic culture wells, AK-8 cells produce lymphokines but are unable to proliferate. Proliferation takes place using the same stimuli upon addition of interleukin 1 (IL 1). Autocrine growth induced by anti-TcR, anti-CD3 or by antigen is dependent on IL 4 and not on IL 2 in this cell line, as shown by the effect of antibodies against IL 4 or the IL 2 receptor. Similarly to plastic-adsorbed antibodies, phorbol myristic acetate (PMA) or a combination of PMA and the calcium ionophore Ionomycin also induces secretion of growth factors without inducing proliferation, but in this case addition of IL 1 is ineffective in inducing AK-8 proliferation. When incubated with anti-TcR or anti-CD3 antibodies in soluble form these cells neither proliferate nor produce IL 4 even in the presence of IL 1. However, soluble antibodies in the presence of IL 1 induce enhanced expression of IL 2 receptors, as measured both by induction of responsiveness to exogenous IL 2 or flow cytometry analysis using anti-IL 2 receptor antibodies. These results show that the pathways for the activation of growth factor receptor expression and the induction of lymphokine secretion can be differentiated in this cell line using anti-TcR or anti-CD3 reagents in different physical forms. The transmembrane signals delivered by these different forms of anti-receptor antibody may allow an understanding of these distinct requirements for T cell growth.

Animals↗

PubMed1994

Cross-linking CD28 leads to activation of 70-kDa S6 kinase.

Proliferation of T lymphocytes in response to antigen/MHC complexes is dependent upon the presence of a co-stimulatory signal; in its absence, T cells are rendered unresponsive to specific antigen CD28 is a T cell surface glycoprotein that acts as a co-stimulatory molecule when combined with signals initiated by the T cell receptor CD3 complex. While the biochemical signaling events following CD28 stimulation are still poorly defined, monoclonal antibodies (mAb) directed against CD28 have been shown to transduce a variety of early signals that are different in the presence of cross-linking antibody or the presence of phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C (PKC). Stimulation of human T cells with cross-linked anti-CD28 mAb alone resulted in the activation of 70-kDa (p70) S6 kinase, a rapamycin-sensitive serine/threonine kinase that is believed to be important for cell cycle progression. Activation of p70 S6 kinase through CD28 was inhibited by rapamycin. Activation of p70 S6 kinase also increased in response to cross-linked CD3, but followed a more rapid time course than activation via CD2. Cyclosporin A and FK506 had no effect on p70 S6 kinase activity initiated via either pathway. The combination of cross-linked CD28 and cross-linked CD3 had no more than an additive effect on the induction of p70 S6 kinase activity. Thus, recruitment of p70 S6 kinase activity appears to represent a common signal transduction event shared by both the CD28 and CD3 pathways of T cell activation.

CD28 Antigens↗

PubMed1994

Human immunodeficiency virus type 1 Nef protein down-regulates transcription factors NF-kappa B and AP-1 in human T cells in vitro after T-cell receptor stimulation.

Human immunodeficiency virus type 1 (HIV-1) negative factor (Nef) has been shown to down-regulate the transcription factors NF-kappa B and AP-1 in vitro. To define the mechanism of action of the Nef protein, the signal transduction pathways which may be affected in T cells by constitutive expression of the nef gene were examined. Stimulation of T cells with tumor necrosis factor, interleukin-1, or lipopolysaccharide resulted in the recruitment of transcriptional factors to a similar level whether or not the cells expressed the nef gene. On the other hand, stimulation of T cells by mitogens or antibodies to the T-cell receptor (TCR)-CD3 complex resulted in the down-regulation of transcriptional factors NF-kappa B and AP-1 in cells expressing the nef gene compared with cells not expressing the nef gene. Because the Nef protein does not affect the surface expression of the CD3-TCR complex, we conclude that the Nef protein down-regulates the transcriptional factors NF-kappa B and AP-1 in T cells in vitro through an effect on the TCR-dependent signal transduction pathway.

Antigens, CD↗

PubMed1999

Molecular mechanisms in the TCR (TCR alpha beta-CD3 delta epsilon, gamma epsilon) interaction with zeta 2 homodimers: clues from a 'phenotypic revertant' clone.

The association between the TCRalphabeta-CD3gammaepsilondeltaepsilon hexamers and zeta2 homodimers in the endoplasmic reticulum (ER) constitutes a key step in TCR assembly and export to the T cell surface. Incompletely assembled TCR-CD3 complexes are degraded in the ER or the lysosomes. A previously described Jurkat variant (J79) has a mutation at position 195 on the TCR Calpha domain causing a phenylalanine to valine exchange. This results in a lack of association between TCRalphabeta-CD3gammaepsilondeltaepsilon hexamers and zeta2 homodimers. Two main hypotheses could explain this phenomenon in J79 cells: TCR-CD3 hexamers may be incapable of interacting with zeta2 due to a structural change in the TCR Calpha region; alternatively, TCR-CD3 hexamers may be incapable of interacting with zeta2 due to factors unrelated to either molecular complex. In order to assess these two possibilities, the TCR-CD3 membrane-negative J79 cells were treated with ethylmethylsulfonate and clones positive for TCR membrane expression were isolated. The characterization of the J79r58 phenotypic revertant cell line is the subject of this study. The main question was to assess the reason for the TCR re-expression. The TCR on J79r58 cells appears qualitatively and functionally equivalent to wild-type TCR complexes. Nucleotide sequence analysis confirmed the presence of the original mutation in the TCR Calpha region but failed to detect compensatory mutations in alpha, beta, gamma, delta, epsilon or zeta chains. Thus, mutated J79-TCR-CD3 complexes can interact with zeta2 homodimers. Possible mechanisms for the unsuccessful TCR-CD3 interaction with zeta2 homodimers are presented and discussed.

Cell Membrane↗

PubMed1990

The phosphorylation of the CD3 gamma chain of T lymphocytes is modulated by beta-endorphin.

The neuropeptide beta-endorphin can modulate the response of T and B cells to mitogenic or antigenic stimulation. In the present report we describe a novel mechanism by which beta-endorphin can interfere with T cell activation. It is shown here that beta-endorphin can modulate the phorbol ester-induced phosphorylation of the gamma chain of the CD3 complex. The effect of beta-endorphin is dose dependent and appears to be mediated via interaction of beta-endorphin with an opiate receptor on lymphocytes. Evidence is presented that the modulatory effect of beta-endorphin is specific for the phosphorylation of the CD3 gamma chain. beta-Endorphin does not affect the phosphorylation of total cell protein, nor does it have any effect on the phosphorylation of the CD4 determinant on T cells. The possible consequence of a change in CD3 gamma chain phosphorylation is discussed.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1991

Primary membrane T cell immunodeficiencies.

Primary membrane T cell immunodeficiencies (ID) have recently been characterized. In this paper we describe the main findings about the leukocyte adhesion deficiencies (LAD), the ID with low expression of the T cell receptor/CD3 complex, and the Omenn's syndrome. LAD is a consequence of mutations in the beta-chain-encoding gene of the leukocyte adhesion proteins. Functional consequences mainly affect phagocytic cells which are incapable of transendothelial migration. Effector T lymphocyte functions are, however, also impaired, i.e., helper T cell activity and cytotoxicity. The latter defect may account for the inability of LAD patients to reject HLA nonidentical bone marrow. Low expression of the T cell receptor CD3 complex is a rare entity characterized by a profoundly diminished expression of the whole complex on all T cells. The basic defect has not yet been unravelled. Interestingly, such T cells differentiate normally and can be activated by some antigens while anti-CD3 and anti-CD2 antibodies are not efficient. In five patients with Omenn's syndrome (combined immunodeficiency with eosinophilia), oligoclonal T cells were detected in blood, skin, and gut. These T cells are also in vivo activated. Since in one family, one sibling presented with typical SCID, i.e., alymphocytosis, and another with the Omenn's syndrome, it is proposed that the latter syndrome may correspond to a form of leakiness of SCID as found in the mice SCID model.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1991

Mitogen-induced IL-2 production and proliferation at defined stages of T helper cell development.

Th cell development inside the thymus can be defined on the basis of qualitative and quantitative CD4 and CD8 marker expression and follows the pathway of CD4-8- cells----CD4+8+ cells----CD4+8low cells----CD4+8- cells, which presumably emigrate to seed the periphery and serve as functionally mature Th cells. The various cell subpopulations at defined developmental stages were isolated by electronic cell sorting and examined for mitogen induced IL-2 production and cell proliferation responses. For TCR-alpha beta-bearing CD4+8+ and CD4+8low thymocytes that are actively engaged in positive and negative selection processes, negligible to low levels of IL-2 production and cell proliferation were observed in response to TCR:CD3 triggering or to the combined activation of protein kinase C and calcium mobilization mediated by PMA and ionomycin, respectively. For CD4-8- TCR-alpha beta early thymocytes that have not yet entered the selection process, PMA + ionomycin induced significant cell proliferation but little IL-2 production, in the absence of added IL-1. However, addition of IL-1 caused a powerful induction of IL-2 production that was accompanied by increased cell proliferation. Triggering of the TCR:CD3 complex had no effect on CD4-8-TCR(-)-alpha beta thymocytes as they do not express detectable levels of TCR-alpha beta. For thymus CD4+8- Th cells, the first cells that have completed TCR repertoire selection, vigorous proliferation was observed in response to TCR:CD3 triggering in the presence of added IL-2. However, the development of IL-2 responsiveness was not accompanied by high level IL-2 inducibility as TCR:CD3 triggering caused only marginal IL-2 production. In contrast, spleen CD4+8- T cells, the most "mature" representatives of Th cells, expressed high levels of IL-2 production as well as IL-2 responsiveness in response to TCR:CD3-mediated stimulation. The lack of anti-TCR-induced IL-2 production by thymus CD4+8- T cells was not due to an intrinsic defect as high levels of IL-2 production was induced by PMA + ionomycin. Possible reasons for the temporal acquisition and differential control of IL-2 inducibility and IL-2 responsiveness are discussed in the context of established Th cell development pathway.

Animals↗

PubMed1997

NK1.1+ CD4+ T cells lose NK1.1 expression upon in vitro activation.

NK1.1+ CD4+ T cells produce IL-4 promptly in vivo upon injection of anti-CD3 and may play a role in initiating Th2 cell-mediated immunity. To characterize their in vitro activation properties, NK1.1+ CD4+ T cells were obtained in high purity from spleens of normal C57BL/6 mice, where they represent 2 to 5% of CD4+ T cells, or from MHC-class II I-Ab gene knockout mice, where they constitute 42% of CD4+ T cells. Activation of NK1.1+ CD4+ T cells from either source with plate-bound anti-CD3 resulted in loss of expression of NK1.1 as determined both by flow cytometric analysis and by reverse transcriptase-PCR analysis. A portion of these cells also lost CD4 expression. Both the CD4+ and CD4- activated cells retained the over-representation of V beta8 and V alpha14 chains and expressed the intermediate levels of the TCR-CD3 complex that is characteristic of resting NK1.1+ CD4+ T cells. The anti-NK1.1 mAb used for cell sorting was not the cause of NK1.1 or CD4 disappearance, since the sorted cells remain both NK1.1+ and CD4+ when cultured in the absence of anti-CD3 or in the presence of anti-CD3 and cyclosporin A. Furthermore, NK1.1+ CD4+ T cells that were not treated with anti-NK1.1 Ab also lost NK1.1 expression after activation. Populations of activated CD4+ and CD4- cells (derived from NK1.1+ CD4+ T cells) produced both IL-4 and IFN-gamma upon restimulation with plate-bound anti-CD3.

Animals↗

PubMed1991

Primary structure and ontogeny of an avian CD3 transcript.

The structure of a chicken CD3 chain has been determined by isolating a cDNA clone (T11.15) that encodes a 175-amino-acid-long protein, including the NH2-terminal signal peptide. In Northern blot experiments, the earliest expression of the T11.15 transcript was detected in the thymus at embryonic day 10 (i.e., 1 day after cytoplasmic expression of a CD3 epitope recognized by a specific monoclonal antibody [CT3; Chen, C.L.H., Ager, L.L., Gartland, G.L. & Cooper, M.D. (1986) J. Exp. Med. 164, 375-380], but 2 days before the appearance of clonotypic components of the T-cell antigen receptor). Sequence similarity of this chicken protein sequence compared with that of the known mammalian CD3 gamma and delta polypeptides was 36-39% and 39-40%, respectively. Amino acid sequence alignments between avian and mammalian CD3 revealed maximum conservation in the transmembrane and cytoplasmic domains as well as in the regions flanking the cysteine residues in the extracellular domain, underlining their functional importance. The difficulty of unambiguously assigning this chain to a single mammalian CD3 subunit on the basis of sequence comparison raises the possibility that this polypeptide represents a derivative from an ancestral form of the gamma and delta chains. It is thus possible that a single chain may play the role of both CD3 gamma and delta subunits in the chicken CD3 complex or, alternatively, that gene duplications occurred independently in the avian and mammalian lineages.

Amino Acid Sequence↗

PubMed1995

Influence of MHC class I molecules on T-cell proliferation induced by CD3 or Thy-1 stimulation.

We have reported that class I- [and lymphocyte function-associated antigen-1 (LFA-1-)] specific monoclonal antibodies (mAb) inhibit anti-CD3-mediated activation of naive T cells. The present study investigated the mechanism of this inhibition. CD28-specific mAb augmented stimulation induced by soluble CD3 mAb, but this costimulation was also inhibited by anti-class I or anti-LFA-1 mAb. However, stimulation of T cells was not inhibited when activated B cells were present. Neither B7-1- nor B7-2-specific blocking mAb or soluble CTLA-4, CD40 or gp39 restored the inhibition. Thus, other molecules expressed on activated B cells are implicated for T-cell activation, which could compensate blockade of class I or LFA-1 molecules. Inhibition induced by class I-specific mAb could potentially be mediated through extracellular, transmembrane or cytoplasmic domains of the target molecules. These possibilities were evaluated by the use of mice transgenic for the Qa-2 molecule, selected for expression of Qa-2 at levels equivalent to classical class I molecules. Qa-2 is inserted in the membrane through phosphatidylinositol linkages. Antibodies directed to Qa-2 inhibited CD3-induced stimulation, demonstrating that cytoplasmic and transmembrane protein sequences of class I molecules are not necessary for the inhibitory effect. Inhibition thus presumably depends on extracellular domains. Finally, T cells from beta 2-microglobulin knock-out mice responded to CD3-specific mAb as well as their class I-positive littermates. Nevertheless, stimulation of T cells from these mice with mitogenic anti-Thy-1 mAb was markedly reduced. Signalling by Thy-1 and the CD3 complex may normally occur through pathways in which class I molecules are implicated.

Animals↗

PubMed1993

Restoration of T cell development in RAG-2-deficient mice by functional TCR transgenes.

Introduction of TCR alpha transgene, TCR beta transgene, or both into RAG-2-/-mice differentially rescues T cell development. RAG-2-/- mice have small numbers of TCR-CD4-CD8-(double negative, DN) thymocytes that express CD3 gamma delta epsilon and zeta proteins intracellularly. Introduction of a TCR beta transgene, but not a TCR alpha transgene, into the RAG-2-/- background restored normal numbers of thymocytes. These cells were CD4+CD8+ (double positive, DP) and expressed small amounts of surface TCR beta chain dimers in association with CD3 gamma delta epsilon but not zeta. RAG-2-/- mice that expressed alpha and beta TCR transgenes developed both DP and single positive thymocytes. Thus, the TCR beta subunit, possibly in association with a novel CD3 complex, participates in the DN to the DP transition.

Animals↗

PubMed1996

Induction of apoptosis by anti-CD3 epsilon F(ab')2 in antigen receptor transgenic murine T cells activated by specific peptide.

Peripheral T cell tolerance can be achieved through deletion of mature CD4+ cells activated by high dose Ag. We tested whether apoptosis of peripheral CD4+ cells could be induced by a stimulatory dose of Ag plus a soluble ligand to the nonpolymorphic epsilon-chain of the TCR-associated CD3 complex. CD4+ T cells from the DO10 mouse express a transgenic TCR-alphabeta specific for OVA peptide 323-339 presented by I-A(d). OVA alone induced clonal activation and expansion of peripheral CD4+/TCR transgene+ cells. Simultaneous exposure to specific Ag plus soluble anti-CD3 Fos, a nonmitogenic anti-CD3epsilon genetically engineered F(ab')2-like Ab, blocked expansion and induced death of CD4+/TCR transgene+ cells, but not CD4+/TCR transgene- T cells. In contrast, a mitogenic anti-CD3epsilon Ab induced polyclonal activation and nonselective T cell death. Sequential stimulation by Ag followed by anti-CD3 Fos also induced death of TCR transgene+ cells, whereas stimulation by anti-CD3 Fos followed by Ag did not affect cell viability or function. Anti-CD3 Fos-induced death was associated with DNA fragmentation characteristic of apoptosis, was facilitated by IL-2, and was initiated by stimulation during the S-G2 phases of the cell cycle. Anti-CD3 Fos could induce deletion of Ag-activated T cells by apoptosis in vivo. Thus, a soluble, non-Fc-binding anti-CD3 Ab can induce programmed cell death of Ag-activated peripheral CD4+ T cells by CD3epsilon cross-linking during S or G2. Peripheral T cell deletion by activation-driven apoptosis is under cell cycle control and can be exploited to achieve selective immunosuppression by nonmitogenic anti-CD3epsilon Abs.

Amino Acid Sequence↗