Intrathymic clonal deletion of V beta 6+ T cells in cyclophosphamide-induced tolerance to H-2-compatible, Mls-disparate antigens.

Abstract

Three possible mechanisms have been proposed to explain development and maintenance ofT cell tolerance to self antigens : the inactivation of self-reactive lymphocytes (clonal anergy), their chronic suppression (clonal suppression), and their elimination (clonal deletion) (1, 2). Experimental attempts to prove these three possibilities have been severely limited because of the technical difficulties (2). A more direct approach to assess the cellular basis of tolerance induction, however, is now available by using the fact that the usage of a certain TCR Vo domain is strongly correlated with the reactivity to specific antigens (3-5). By exploiting such correlations, it has been demonstrated that self-tolerance to the products encoded by the Mls-1a allele (4, 5) or the Mls-2a allele (6, 7) is mediated via the clonal deletion of the self-reactive T cell clones .As to tolerance induction to allogeneic antigens, many attempts have been experimentally made . Those include neonatally induced tolerance (8), irradiationinduced tolerance (9-11), and antilymphocyte serum-induced tolerance (12, 13). Recently, MacDonald et al. (14) have indicated that neonatally induced tolerance to Mls-la-encoded antigens was likewise accompanied by the intrathymic elimination of V06-bearing cells, which are capable of recognizing Mls-1a-encoded antigens bound to MHC class II molecules, thus supporting the clonal deletion model. On the other hand, Qin et al. (15) have raised the possibility that tolerance to allograft induced by combining bone marrow transplantation (BMT)1 together with administration of CD4 and CD8 mAb in adult mice is, at least in part, due to clonal anergy rather than deletion . Thus, the underlying mechanisms in the development and maintenance of the donor-specific transplantation tolerance still remain controversial .We have previously reported a method of allo-tolerance induction in adult mice

Induction of Permanent Mixed Chimerism and Skin Allograft Tolerance Across Fully MHC-Mismatched Barriers by the Additional Myelosuppressive Treatments in Mice Primed with Allogeneic Spleen Cells Followed by Cyclophosphamide

“…injection of 1 ϫ 10 8 allogeneic spleen cells (SC) (day 0) followed, 2 days later, by an intraperitoneal i.p. administration of 200 mg/kg CP (on day 2) (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24). By using this method, we were able to readily induce a long-lasting skin allograft tolerance in most of H-2-matched combinations (16 -18) and a B10.A (5R) (K b , IA b , IE b , D d ; Thy-1.2) into B10.Thy-1.1 (H-2 b ; Thy-1.1) combination (19), but not in fully H-2-mismatched combinations (13,19).…”

Efficacy and Limitations of Cyclophosphamide‐induced Tolerance against αGal Antigen

“…This has been previously described as occurring during the induction period of T-cell tolerance in a CP-induced tolerance protocol [8,10]. The progenitor cells of anti-aGal nAb-producing B cells are thought to arise from B1-b cells in peritoneal and pleural cavities, and plasma cells mature in secondary lymphoid organ such as the spleen to produce anti-aGal Ab [25].…”

“…According to our previous methods [8][9][10], the statistical significance in the data of graft survival was determined by Mann-Whitney U-test. For other data, the Student's t-test was used to calculate significance.…”

“…injection of 1 Â 10 8 allogeneic spleen cells (SC) (day 0) followed, 2 days later, by an i.p. administration of 200 mg/kg of CP in mice [7][8][9][10]. By using the H-2-matched murine combination of AKR into C3H and MoAbs against the T-cell markers (Thy1.1 and Thy1.2) and Mls-a reactive TCR Vb6, we have demonstrated the concurrent mechanisms of CP-induced tolerance.…”

“…By using the H-2-matched murine combination of AKR into C3H and MoAbs against the T-cell markers (Thy1.1 and Thy1.2) and Mls-a reactive TCR Vb6, we have demonstrated the concurrent mechanisms of CP-induced tolerance. These mechanisms are: (i) clonal destruction of antigenstimulated and then proliferating T cells by CP [8,9], (ii) establishment of stable mixed chimerism [11], (iii) intrathymic clonal deletion [8,9] and (iv) and regulatory mechanisms at the late stage of tolerance [12]. Recently, we have developed a modified method that includes additional myelosuppressive treatments and induces both permanent mixed chimerism and skin allograft tolerance in H-2 mismatched combinations [10].…”