Qa-1 and Qa-2 expression on CFU-s.

Multipotential stem cells can be detected in bone marrow cells preparations by injecting these cells into syngeneic irradiated hosts. Colonies (CFU-s) are visible macroscopically on the spleen after 8 days. Pretreatment of A-Tlab (Qa-1.2) bone marrow with A-anti-A-Tlab serum (anti-Qa-1.2), in the presence of complement, reduced CFU-s by 80% whereas A-Tlab anti-A serum (anti-Qa-1.1) treatment had no effect. Pretreatment of A(Qa-1.1) bone marrow with A-Tlab anti-A serum reduced macroscopic splenic colonies by 78%. Similar results were obtained by using C57BL/6 (Qa-1.2) and B6-Tlaa (Qa-1.1) bone marrow. Thus, both Qa-1.1 and Qa-1.2 are expressed on CFU-s. Qa-2 expression on CFU-2 was examined in the same manner. B6.KI anti-B6 (anti-Qa-2,3) serum reduced CFU-s numbers by 87% on B6 (Qa-2,3+) while having little or no effect on B6.KI (Qa-2,3-). Treatment with D3.262, a monoclonal anti-Qa-2 antibody, reduced B6 CFU-s by 80%, and had no effect on B6.KI CFU-s. Detection of Qa-1 and Qa-2 on CFU-s underscores the wide distribution of the Qa antigens in the hematopoietic system.