Studies on the mechanism of stimulation of the humoral response of murine spleen cultures by culture fluids from human monocytes.

It has been demonstrated that media derived from cultures of human monocytes can stimulate the IgM and IgG anti-sheep erythrocyte response of normal or T cell-deficient murine splenocytes in vitro. This culture fluid also causes a slight stimulation in the rate of B cell division and in the number of antibody-secreting cells occurring in the absence of added antigen. The active factors, which are released from the monocytes during the first 2 days of culture, appear to affect the murine B cells throughout the culture period.