INFLUENCE OF THE Ag-B LOCUS ON REACTIVITY TO SKIN HOMOGRAFTS AND TOLERANCE RESPONSIVENESS IN RATS

Abstract

SUMMARY The case with which rats of one strain can be rendered tolerant of skin grafts from another strain is correlated with their Ag-B genotypes and not with the median survival time of skin grafts exchanged between them. Thus, although adult Lewis recipients reject Ag-B-compatible Fischer skin grafts as promptly as they reject Ag-B-incompatible BN or DA skin grafts, Lewis recipients are much more easily rendered unresponsive of Fischer skin grafts than of BN or DA grafts. Where Ag-B compatibility prevails, tolerance is inducible with relatively low dosages (≤1 million) of cells originating from all components of the lymphohematopoietic tissue system, including the thymus. On the other hand, when donor and host differ at this locus not only are much higher numbers of cells required to induce tolerance, but there are wide disparities in the tolerance-conferring capacity of different cell types. Bone marrow is superior to spleen which, in turn, is better than lymph nodes; thymocytes are practically ineffective. Evidence is also presented which suggests that the facility with which tolerance can be abolished by transfer of isologous cells is a function of the dosage of the inoculum used to induce tolerance. The importance of the Ag-B locus in determining susceptibility to runt disease is also considered.