Human myeloma cells and their strong stimulating capacity in 'one-way' mixed lymphocyte reaction: a comparative study with leukaemic B lymphoid cells.

Cultured human myeloma cells (ARH-77, RPMI-8226 and U-266), like leukaemic B lymphoid cells, consistently exerted a strong stimulating capacity on allogeneic lymphocytes in the 'one-way' mixed lymphocyte reaction. An optimal stimulation was seen when a 1:1 ratio or 1:2 ratio of responding cell:stimulating cells of each cell line was utilized. The stimulating capacity of ARH-77 or RPMI-8226 cells was significantly diminished when a 1:4 ratio of responding cells:stimulating cells was utilized. Fresh bone marrow cells containing more than 80% plasma cells from a patient with multiple myeloma, on the other hand, failed to exert the stimulating capacity on two occasions. The striking difference between cultured myeloma cells and fresh plasma cells is that the Ia-like antigen is present on cultured myeloma cells, and this antigen is absent on fresh plasma cells. The relationship between the Ia-like antigen and the stimulating capacity in 'one-way' mixed lymphocyte reaction is discussed.