TOLERANCE TO NON-H-2 HISTOCOMPATIBILITY ANTIGENS

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Abstract
Transplantation tolerance may be a result of positive immunoregulation rather than simply unresponsiveness attributable to a lack of competent effector cells. Tolerance of the H-Y and H-1 histocompatibility antigens [Ag] is mediated by a population of thymus-derived lymphocytes. A suppressor cell to the H-Y antigen probably exists. Female mice rendered tolerant of the H-Y Ag by neonatal exposure to male lymphoid cells or by multiparity accept male skin grafts indefinitely, but inactivate male peritoneal exudate cells (PEC) in a 2nd-set fashion. Tolerance of other non-H-2 Ag may be controlled by a similar mechanism. Using mice congenic with C57BL/10 at the H-4 and H-7 loci, mice rendered tolerant of the H-7a and H-4b Ag by neonatal exposure to histoincompatible lymphoid cells are incapable of rejecting skin or peritoneal cell allografts, suggesting that identical histocompatibility Ag are present on skin and peritoneal cells. Tolerance induced in neonatal mice to the H-4b and H-7a Ag could not be adoptively transferred to syngeneic recipients. Tolerance involving the H-4 and H-7 Ag is most likely because of a clonal inactivation of alloantigen-reactive cells as a consequence of neonatal exposure to Ag.
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