Lymphotoxins: selective cytotoxic effects.

Materials with lymphotoxin activity produced by lectin stimulated primary cultures of human lymphocytes enriched for T cells or B cells, as well as material obtained from established tissue culture lines of human lymphoid cells were tested for cytotoxicity towards a large number of primary cultures and established lines of human and animal cells. Highly selective effects were found. The patterns of responses to the various lymphotoxin preparations indicate heterogeneity not only among the different cell cultures but also among the lymphotoxin preparations. In addition to the heterogeneity of the various cell cultures in their responses to the lymphotoxin preparations, a spectrum of susceptibilities was also noted among clonal derivatives of the same parental lines. In quantitative terms the responses of the most resistant and the most susceptible cell cultures spanned approximately a 200-fold range. These findings could have bearing upon the mechanism of tumor evasion of host antitumor immunity.