Immunogenetic aspects of in vivo allotolerance induction during the ontogeny of Xenopus laevis.

This study describes the ontogeny of allograft immunity in a partially inbred strain of frogs (Xenopus laevis). At various times during the frogs' premetamorphic, perimetamorphic, and postmetamorphic life, major histocompatibility complex (MHC) homozygous strain JJ Xenopus (MHC haplotype j) were grafted with skin from adult donors of defined MHC homozygous (j,f) and heterozygous (j/f,f/h) haplotypes. This protocol reveals that destructive allograft reactivity to MHC alloantigens in Xenopus matures slowly and that allotolerance can be induced to such MHC-encoded antigens throughout larval life. The ultimate fate of an MHC disparate transplant (survival or rejection) is dependent on several interacting variables, which include antigen dose, haplotype dose, and the developmental stage of the host frog at the time of transplantation. In contrast, minor H-locus disparate (MHC compatible) grafts never appear to be rejected by hosts grafted at any larval stage.