Characterization of a spontaneous murine B cell leukemia (BCL ₁). I. Cell surface expression of IgM, IgD, Ia, and FcR

The surface marker expression of a spontaneous B lymphocyte leukemia discovered in a BALB/c mouse (BCL ₁) was examined and found to include a subset of markers known to occur on normal B lymphocytes. The tumor cells bore surface Ig that included both μ- and δ-chains associated with the λ light chain. Alloantigens coded for within the murine MHC, including H-2D, H-2K, and I-region products, were identified on the tumor cells. Although normal B lymphocytes are thought to express products coded for within both the I-A and I-E subregions, the BCL ₁ expressed only normal amounts of I-E subregion products. In addition, the H-2 and IA antigens revealed by 2-dimensional gel electrophoresis exhibited an abnormal pattern of post-translational modifications. The Fc, but not the complement-receptor, was present on the surface of tumor cells. The presence of IgD, Ia antigens, and the responsiveness to lipopolysaccharide (see subsequent paper) have led the authors to postulate that the BCL ₁ tumor represents a later differentiative stage than murine B lymphocyte tumors previously described.