Transformed B cell lines express cell-associated tumor necrosis factor and mediate natural cytotoxic activity

Natural cytotoxic (NC) activity is mediated by a cell-associated form of TNF-alpha. Here, we have characterized the NC-like properties of cloned murine transformed B cell lines. Several B cell lines cause the lysis of NC/TNF-alpha-susceptible target cells, but not NC/TNF-apha-resistant target cells. Furthermore, lysis of targets by B cell lines involves a nonsoluble (i.e., cell-associated) mechanism that is blocked by anti-TNF antibody. Target cells selected for resistance to a B lymphoma cell line expressing NC-like activity are resistant to splenic NC-mediated lysis, resistant to TNF-alpha-mediated lysis, and have increased tumorigenicity in BALB/c mice. Thus, these B cells lines may serve as cloned effectors which lyse cells using a cell-associated TNF-dependent mechanism analogous to NC lysis. Furthermore, it is possible that the expression of TNF by transformed B cells is autostimulatory and is involved in their malignant transformation.