The screening of non-H-2 congenic lines forSk loci.

Thirty-seven histocompatibility congenic lines of mice, including at least 27non- H-2 lines, developed by Bailey on the C57BL/6 background, were screened for loci determining Sk (skin-specific) histocompatibility antigens. Background strain hosts were inoculated with lymphoid cells from the congenic lines and subsequently challenged with skin test grafts from the same donors. Comparison of the survival times of these test grafts with those of first- and second-set skin grafts in the same donor-host combinations suggests that the lymphoid cells from 35 of the congenic lines apparently immunized or tolerized at least some of the hosts. Thus, the histocompatibility antigens involved were shared by lymphoid cells and skin, and by definition could not be Sk antigens. The tests were indecisive with two of the non-H-2 lines, but if Sk antigens were involved, their contribution to the immunogenicity of conventional skin allografts probably was negligible. Hence ifSk congenic lines are desired, they probably will have to be developed on their own by procedures specifically designed to select for Sk antigens of significant immunogenicity.