WEB 2170 diminished the production of immunoglobulin (Ig) in cultures of mixed follicular dendritic cells (FDCs) and B lymphocytes. Mixed tonsillar B lymphocytes and FDCs were cultured together with or without the indicated concentrations of WEB 2170 in 24 well plates for 7 days. On day 7, supernatants were harvested and used for measuring total IgG or IgM. The histograms indicate the percentage decrease in IgG (A) and IgM (B) from cultures untreated by WEB 2170 (values are indicated in the text) (n = 5). B = B lymphocytes; F = FDCs; W = WEB 2170. *p < .05.