Two types of TNF receptors are expressed on human normal and malignant B lymphocytes.

We analyzed the expression of the 75- and 55-kDa tumor necrosis factor (TNF) receptors on the surface of human normal and malignant B cells. Freshly isolated tonsillar B cells do not express detectable amounts of receptors. After 24 hr of stimulation with anti-IgM and low-molecular-weight (l.m.w.) BCGF, B cells express the 75-kDa receptor but not the 55-kDa receptor, but after 48 hr of stimulation both types of receptors are expressed. Three of 10 patients with B-chronic lymphatic leukemia or hairy cell leukemia (HCL) had a small population of TNF receptor positive tumor cells; after in vitro stimulation of tumor cells in 10/10 patients various patterns of 75- and 55-kDa TNF receptor expression were found. MAb UTR-1, which binds the 75-kDa receptor, inhibits the l.m.w. BCGF-induced [3H]thymidine incorporation of cultured tonsillar B cells and HCL cells. This may provide evidence that in B cells the 75 kDa TNF receptor molecule is functionally active.