Evidence for the time of appearance of H-2 antigens in mouse development

A vigorous round cell reaction, followed by destruction of the graft, ensues when C57BL/10 embryos of S days or more of development are grafted to adult B10.D2 hosts preimmunized with C57BL/10 tissues. Since the strains differ only at the H-2 locus, and since the cellular infiltrate does not occur when syngeneic embryo grafts are made, the reaction is taken as evidence for the expression of H-2 antigens in the 8-day embryo. Results with younger embryos suggest that H-2 first appears on the membrane around day 7 of development, since grafts of 7-day embryos provoke a strong reaction within 3 days of grafting, while most grafts until the of 6-day embryos do not provoke a reaction until the 3rd or 4th day after grafting.