Abstract
Earlier tests for the H-Y (male) antigen in mice were limited to male graft rejection by syngeneic females. The experiments described in this report attest to the specificity of a new serological test for this antigen. Anti-H-Y sera and immune ascites fluid with statistically significant cytotoxic indices were produced in C57BL/6Ha females; a cytotoxicity test of sufficient sensitivity to detect and titrate cytotoxic activity, or, conversely, to detect the presence of the male antigen on C57BL/6Ha male lymphoid cells in vitro, was devised.