Evidence that murine hematopoietic cell subset marker J11d is attached to a glycosyl-phosphatidylinositol membrane anchor.

Glycosyl-phosphatidylinositol (G-PI) has been shown to serve as membrane anchor for cell surface molecules such as Thy-1, Ly-6-controlled ThB and Qa antigens. Here, we present several lines of evidence indicating that the hematopoietic cell lineage (i.e. thymocytes, B cell subset and red blood cells) marker defined by the rat monoclonal antibody J11d is also a G-PI-linked structure. First, surface expression of the J11d-defined molecules, and that of the related antigen B2A2, was found to be specifically reduced by treatment of thymocytes and B lymphoma or hybridoma cells with excess of Staphylococcus aureus PI-specific phospholipase C; this enzyme also solubilizes a 35-40-kDa material from erythrocyte microsomal membranes corresponding to the predominant J11d-reactive red cell surface molecules. Second, Thy-1- mutants of the BW5147, T1M1, S1A or S49 murine T lymphoma cells of the complementary classes A, B, C and E (i.e. shown to be defective in the enzymatic machinery that posttranslationally modify Thy-1 molecules) also lack J11d, or express it at a very low level. Although directed at a G-PI-linked structure, the J11d monoclonal antibody, unlike other reagents to Thy-1 or Ly-6-controlled antigens, failed to induce thymocyte proliferation even in the presence of phorbol myristate acetate and cross-linker monoclonal antibody.