Clonal deletion of postthymic T cells: veto cells kill precursor cytotoxic T lymphocytes.

Veto cell-mediated suppression of cytotoxic T lymphocyte (CTL) responses has been proposed as one mechanism by which self-tolerance is maintained in mature T cell populations. We have previously reported that murine bone marrow cells cultured in the presence of high-dose interleukin 2 (IL-2) (activated bone marrow cells [ABM]) mediate strong veto suppressor function. To examine mechanisms by which ABM may suppress precursor CTL (p-CTL) responses, we used p-CTL generated from spleen cells of transgenic mice expressing a T cell receptor specific for H-2 Ld.

Differential T cell hyporesponsiveness induced by in vivo administration of intact or F(ab')2 fragments of anti-CD3 monoclonal antibody. F(ab')2 fragments induce a selective T helper dysfunction.

Induction of peripheral T cell anergy associated with stimulation through the TCR complex in vivo has been described in mice using chemically modified APC, staphylococcal enterotoxin B, and intact anti-CD3 mAb. In the latter two models, T cell proliferation, IL-2R expression, and lymphokine production have been demonstrated before subsequent induction of hyporesponsiveness, whereas in the former model, these events have not been observed. To further investigate the relationship between mitogenicity and induction of peripheral hyporesponsiveness, mice were treated with either mitogenic intact anti-CD3 mAb or nonmitogenic F(ab')2 fragments of anti-CD3 mAb.

In vivo administration of anti-CD3 monoclonal antibodies or immunotoxins in murine recipients of allogeneic T cell-depleted marrow for the promotion of engraftment.

The role of host anti-donor cells in rejection of fully allogeneic donor T cell-depleted marrow was investigated by using mAb or immunotoxins directed against T cell or NK cell determinants. Immunotoxins consisting of mAb conjugated to a low oligosaccharide-containing fraction of purified ricin toxin A chain (RTA) facilitated in vivo-depletion of target cell populations. BALB/c and DBA/1 donors were selected based upon their expression (BALB/c) or lack of (DBA/1) hemopoietic histocompatibility (Hh1) Ag, which may serve as targets for donor rejection in C57BL/6 hosts.

Cigarette smoking: risk factor for premature facial wrinkling.

Objective: To determine if cigarette smoking is a risk factor for the development of premature facial wrinkling.

Design: Cross-sectional study.

Setting: Smoking cessation clinic and community.

T-lymphocyte interleukin 2-dependent tyrosine protein kinase signal transduction involves the activation of p56lck.

Addition of interleukin 2 (IL-2) to IL-2-dependent T cells results in tyrosine protein kinase signal transduction events even though the IL-2 receptor alpha and beta chains lack intrinsic enzymatic activity. Here we report that addition of IL-2 to IL-2-dependent human T cells transiently stimulates the specific activity of p56lck, a member of the src family of nonreceptor tyrosine protein kinases expressed at high levels in T lymphocytes. The ability of IL-2 to induce p56lck activation was found to be independent of the capacity of p56lck to associate with either CD4 or CD8.

No T-cell tyrosine protein kinase signalling or calcium mobilization after CD4 association with HIV-1 or HIV-1 gp120.

The T lymphocyte surface protein CD4 is an integral membrane glycoprotein noncovalently associated with the tyrosine protein kinase p56lck. In normal T cells, surface association of CD4 molecules with other CD4 molecules or other T-cell surface proteins, such as the T-cell antigen receptor, stimulates the activity of the p56lck tyrosine kinase, resulting in the phosphorylation of various cellular proteins at tyrosine residues. Thus, the signal transduction in T cells generated through the surface engagement of CD4 is similar to that observed for the class of growth factor receptors possessing endogenous tyrosine kinase activity.

Purged autologous bone marrow transplantation in the treatment of acute leukemia.

Allogeneic bone marrow transplantation is an established treatment for acute leukemia. It is largely limited to patients with HLA-matched sibling marrow donors and those for whom phenotypically HLA-matched unrelated donors can be identified. There therefore exists a significant number of patients for whom this potentially curative therapy is not available.

The human antimurine xenogeneic cytotoxic response. I. Dependence on responder antigen-presenting cells.

We have examined the role of the human responder APC in the generation of CTL responses to xenogeneic antigens. Of six xenogeneic responses evaluated, only the human antimurine response was dependent on human APC for CTL generation. APC requirements for the other five xenogeneic responses more closely resembled those observed in the generation of human or murine alloreactive CTL.

Anti-CD3 F(ab')2 fragments are immunosuppressive in vivo without evoking either the strong humoral response or morbidity associated with whole mAb.

The use of anti-CD3 monoclonal antibodies to treat organ allograft rejection has been complicated by (1) the morbidity associated with the initial dose, (2) the humoral response of the patients against the mAbs, and (3) the generalized immunosuppression induced by the mAbs. We investigated the potential of F(ab')2 fragments of the anti-murine-CD3 mAb, 145-2C11, to avoid these complications in the murine model. Both whole mAb and F(ab')2 fragments induced T cell depletion.

Interleukin 2 enhancement of veto suppressor cell function in T-cell-depleted bone marrow in vitro and in vivo.

In allogeneic bone marrow transplantation, graft-versus-host disease can be prevented by the removal of T cells from the donor marrow. The risk of marrow graft rejection is however greater for T-cell-depleted marrow than nondepleted marrow. Cells with a specific type of suppressor activity, termed veto cells, which might depress the host rejection response, have been reported to be present in murine marrow.

Graft rejection by cytolytic T cells. Specificity of the effector mechanism in the rejection of allogeneic marrow.

Cellular effector mechanisms of allograft rejection remain incompletely described. Characterizing the rejection of foreign-marrow allografts rather than solid-organ grafts has the advantage that the cellular composition of the marrow graft, as a single cell suspension, can be altered to include cellular components with differing antigen expression. Rejection of marrow grafts is sensitive to lethal doses of radiation in the mouse but resistant to sublethal levels of radiation.

Efficacy of T cell depletion of surgically resected cadaveric marrows by monoclonal antibodies: considerations in HLA-mismatched marrow transplantation.

The potential therapeutic benefits of allogeneic bone marrow transplantation (BMT) remain generally unavailable to patients who have diseases amenable to treatment by allogeneic BMT, but who lack an identifiable HLA-matched marrow donor. If graft versus host disease and graft rejection can be controlled, then the possibility of expanding allogeneic BMT to minimally HLA-matched or fully mismatched combinations exists and a "universal" donor marrow bank might be established. Towards this end, we have evaluated surgical harvest of cadaveric marrow, T cell depletion of such marrow (for prevention of graft-versus-host disease), influence of surgical harvest on final T cell content, and final cell yield.

Interleukin-1 enhances survival of lethally irradiated mice treated with allogeneic bone marrow cells.

Interleukin-1 (IL-1) enhanced the capacity of allogeneic bone marrow (BM) cells to promote survival of mice given doses of radiation (1,200 to 1,350 cGy) that are significantly higher than those generally used for BM ablation (850 to 950 cGy). Three to five times greater numbers of lethally irradiated (1,200 to 1,350 cGy) C57B1/6 (H-2b) mice given 10(7) T-cell-depleted Balb/c (H-2d) BM cells survived over 6 weeks if also treated with a single intraperitoneal (IP) dose of 10 micrograms IL-1 20 hours before or from 1 to 3 hours after radiation. The spleens of these mice were reconstituted predominantly, but not exclusively, with donor cells (54% to 91%).

Cardiac allograft survival across major histocompatibility complex barriers in the rhesus monkey following T lymphocyte-depleted autologous marrow transplantation. IV. Immune reconstitution.

Studies of postmyeloablative immune reconstitution have been reported for allogeneic bone marrow transplantation and also for non-T cell-depleted autologous/syngeneic BMT. However, there is a paucity of information regarding immune recovery following T cell-depleted autologous/syngeneic BMT. We have developed a primate transplantation tolerance model in which rhesus monkeys were conditioned with total-body irradiation and extensively T cell-depleted autologous BMT and given a major histocompatibility complex-mismatched heterotopic cardiac allograft.

Cardiac allograft survival across major histocompatibility complex barriers in the rhesus monkey following T lymphocyte-depleted autologous marrow transplantation. III. Late allograft rejection.

We have studied organ allograft survival in rhesus monkeys conditioned with myeloablative total-body irradiation and T cell-depleted autologous bone marrow transplantation then given a heterotopic MHC-mismatched cardiac allograft in the immediate postmyeloablative period. This model has enabled us to investigate the role of T cells in vascularized organ allograft rejection. We previously reported (1) that recipients of marrow depleted of T cells below a critical threshold (0.

Restriction fragment length polymorphism analysis with a cross-reactive HLA class II DR-beta gene probe for the detection of engraftment of MHC-mismatched marrow in the rhesus monkey.

Our interest in MHC-mismatched allogeneic bone marrow transplantation (BMT) in the rhesus monkey prompted us to investigate restriction fragment length polymorphism analysis as a means for detecting lymphohematopoietic chimerism in the primate. A human MHC (HLA) class II DR beta gene cDNA probe was tested on rhesus peripheral blood mononuclear cell DNA digested with any of three restriction enzymes. We found that (1) the human DR beta probe hybridized to as many as 15 restriction fragments per rhesus DNA sample, suggesting cross-hybridization at more than one locus of rhesus MHC class II beta genes; (2) restriction fragment length polymorphisms were common among outbred monkeys as a result of class II beta gene polymorphisms and would be sufficient for chimerism detection in the majority of random pairs of outbred monkeys utilizing only a single restriction enzyme (Bgl II); and (3) sensitivity (5-10% chimerism) was comparable to that reported for restriction fragment length polymorphism assays utilizing non-MHC probes in clinical HLA-identical BMT.

Fine specificity of xenogeneic antigen recognition by human T cells.

T cell mediated responses play a role in xenograft as well as allograft rejection. In vitro T cell responses to xenogeneic antigens are characterized by T cell recognition of polymorphic determinants of gene products encoded by the major histocompatibility complex of the stimulating cells, but little is known of the fine specificity of this recognition of xenogeneic antigens and its comparability to allogeneic antigen recognition. In order to study the fine specificity of human CTL in the recognition of xenogeneic antigens, long-term lines or clones were established from a secondary mixed lymphocyte response in which the stimulator cells were H-2b murine splenocytes.

Suppression of the humoral response to anti-CD3 monoclonal antibody.

Anti-CD3 monoclonal antibodies are used clinically to treat organ allograft rejection. Their administration can result in reversal of rejection even in episodes resistant to other modes of therapy. A major limitation to their use has been the humoral response of the patients against the mAbs, resulting in loss of therapeutic efficacy.

Common epitope in human immunodeficiency virus (HIV) I-GP41 and HLA class II elicits immunosuppressive autoantibodies capable of contributing to immune dysfunction in HIV I-infected individuals.

We previously reported the identification of highly conserved homologous regions located in the carboxy terminus of the HIV I gp41-envelope (aa 837-844), and the amino-terminal of the beta chain of all human HLA class II antigens (aa 19-25). Murine monoclonal antibodies, raised against synthetic peptides from these homologous regions, bound not only to the isolated peptides, but also to the native gp160 and class II molecules. In this study one-third of sera from HIV I-infected individuals, at different disease stages, were found to react with both the gp41 and class II-derived peptides.

Inhibition of cytotoxic T cell lysis by anti-CD8 monoclonal antibodies: studies with CD3-targeted cytolysis of nominal antigen-negative targets.

The function of the CD8 molecule in lympholysis mediated by cytotoxic T cells was investigated by examining possible contributions of ligands on the target cell to the inhibition of lysis observed with CD8-specific mAb. In order to evaluate a variety of target cells, including those not expressing the nominal Ag (NA) for which the CTL was specific, lysis was effected by cross-linking the CTL and the target cells with anti-CD3 mAb. Such CD3 redirected cytotoxicity was demonstrated to be inhibited by anti-CD8 mAb when low anti-CD3 mAb concentrations were used.

Cardiac allograft survival across major histocompatibility complex barriers in the rhesus monkey following T lymphocyte-depleted autologous marrow transplantation. II. Prolonged allograft survival with extensive marrow T cell depletion.

In the present study, we tested the possibility that a vascularized allograft might induce immunological tolerance in a myeloablated host, similar to the tolerance induced by allogeneic bone marrow grafts. To this end, we developed a rhesus monkey model consisting of myeloablative total-body irradiation and T cell-depleted autologous marrow transplantation followed by MHC-mismatched heterotopic cardiac allograft implantation. Limiting dilution analysis was used to quantify residual marrow T cells following depletion.