Maturation of transplantation antigens in Ambystomamexicanum

Both juvenile (14–16 week) and adult (18 month) $\text{Ambystoma}$$\text{mexicanum}$ reject skin allografts from adult $\text{Ambystoma}$ more speedily than they reject such grafts from juvenile axolotls. Donor-specific histocompatibility antigen, prepared from splenocytes, is more effective in inhibiting adult host splenocyte migration when the antigen is prepared from spleen cells from adult, rather than from juvenile $\text{Ambystoma}$. The thymus is fully developed in juvenile $\text{Ambystoma}$, suggesting that the delayed kinetics of rejection of juvenile allografts reflects immaturity in the expression of histocompatibility antigens to donor skin cells.