Many cells in rat bone marrow have cell-surface Thy-1 antigen.

Thy-1.1 and Thy-1 xenoantigenic determinants were detected at the cell surface of many rat bone marrow cells. The absorptive capacity of bone marrow cells was 6-10% of that of thymocytes for Thy-1 antigenic determinants, and 30-45% of rat bone marrow cells were specifically labeled with anti-Thy-1 antibody as detected by autoradiography. Thus, while mice and rats are similar in having large amounts of Thy-1 in brain and thymocytes, they differ in that the rat lacks the antigen in most peripheral T cells and expresses it in a large number of bone marrow cells; the opposite is true in the mouse.