Cultured marrow stromal cells express common acute lymphoblastic leukaemia antigen (CALLA): implications for marrow...

This study demonstrates the presence of an antigenic determinant associated with the common acute lymphoblastic leukaemia antigen (CALLA), and presumably CALLA itself, on stromal cells in normal human long-term marrow cultures by using two monoclonal anti-CALLA antibodies, J-5 and 24.1. Treatment of cultured stromal cells with antibody and complement resulted in the loss of most flat angulated cells and many of the fat-containing cells. However, long-term cultures were generated with cytotoxic antibody-treated marrow buffy coat cells, and the stromal cells in these cultures were also CALLA-positive. We conclude that CALLA-bearing stromal cells arise from CALLA-negative progenitors. CALLA therefore could be either a differentiation antigen acquired on mature marrow stromal cells or may arise as a proliferation-dependent antigen. These studies suggest that the generation of long-term cultures from cytotoxic antibody-treated marrow may be an appropriate in vitro model for the functional assessment of such marrow prior to its use in autologous transplantation.