Repeated isolation of unique Qa2+ Ia+ clonally derived cell lines from Qa2- mice

Qa2+ tumor cell lines were previously isolated from individual BALB/cBy (Qa2-) splenic lymphomas induced by murine sarcoma virus-murine leukemia virus-Moloney (MSV-MuLV-M). Two clonally derived cell lines, ORA I-a and Thorbly, and one noncloned cell line, BOMS, expressed Qa2, but neither Ly-1 nor Ly-2 were detected. In order to determine whether eight cloned and two noncloned tumor cell lines all represented a unique population of transformed cells, the presence of a series of surface differentiation antigens as studied. In addition to Qa2, each cell line examined expressed IAd, IEd, H-2Kd, H-2Dd, and receptors for C3b and the Fc portion of immunoglobulin (Ig). Neither Thy-1.2 nor Ig were detected on the cell surfaces, and cytoplasmic Ig was not precipitated from metabolically radiolabeled and detergent-solubilized cell extracts. However, monocyte specific alpha-napththyl acetate esterase-containing granules were present in all cell lines examined. Therefore, a unique Qa2+ monocytic cell is repeatedly isolated after chronic MSV-MuLV-M infection. Further analysis of these cells may provide insight into both the regulation of Qa2 expression and the interactions between monocytes and lymphocytes during leukemogenesis.