Thymus-Derived Rat Lymphocyte Recepto Nonserologically Defined Product of the 1 Histocompatibility Gene Complex

Rlecogmnition of cell surface antigens by nonsensitized thynmus-derived rat lymphocytes is not affected by antisera agaiinst immunoglobulini, yet cali be effectively blocked by treatment of the lymphocytes with alloantisera raised against lymnphoid cells. However, allo- antisera induced by nonlymphoid cells do not inlhibit recognition. Adsorption of blocking antisera on immuno- globulin-Sepharose columns does not decrease their blockinig activity. Absorption of blocking alloantisera with liver and kidney lhomicogenrates removes tlihe cytotoxic alloantibodies, yet does not affect the capacity of the anti- sera to block recognition. Anti-HI-l alloantisera block antigen recognition onily of lymphocytes of strains that share tlce 111-1 locus. These results suggest that the con- stant part of tlhe thymus-derived lymphocyte receptor for cell-surface aintigens is a product of the rat major hlisto- compatibility locus, which is not identical withi the serologically defined anitigells.