Evidence for expression of Ly-6.2 on non-bone marrow-derived cells in kidney, skin and connective tissues

Mouse alloantigen Ly-6.2 is detectable in various non-lymphoid tissues such as kidney, but it is not clear whether or not this expression is due to bone-marrow derived passenger leukocytes. To determine whether non-marrow derived cells express Ly-6.2, we examined the expression of this antigen in kidney and on isolated connective tissue and epidermal cells. Studies in radiation chimeras demonstrated that the kidney did not become Ly-6.2 positive when negative animals were reconstituted with positive marrow. Thus, passenger leukocytes cannot account for the renal expression of Ly-6.2, indicating that most of this antigen is on non-marrow-derived (parenchymal) cells in kidney. Various isolated cell types--fibroblasts, osteocytes, chondrocytes and skin epidermal cells--were found to be Ly-6.2 positive. Indeed, absorption and cytotoxicity results suggested that the amount of Ly-6.2 on fibroblasts exceeded the amount of an H-2 antigen on these cells. Comparison of fibroblasts to lymphocytes indicated that fibroblasts had 13--60 times more Ly-6.2 than spleen cells and three times more than PHA blasts. The results indicate that the Ly-6.2 detected in non-lymphoid tissues is predominantly on the parenchymal or connective tissue elements of those tissues.