Lyt-1.1 antisera contain antibody against new cell surface alloantigen having wide tissue distribution.

Lyt-1.1 antisera produced in Lyt-1 congenic strain combination are contaminated with additional antibody detecting new cell surface alloantigen showing wide tissue distribution. The antibody was detected by complement independent inhibition of colony forming hemopoietic stem cells. Selective absorption experiments and differences in strain distribution prove that the discovered antigen is different from Lyt-1.