Studies of the cloned (B lymphoma X B lymphocyte) cell line TH2.2 have demonstrated the following: (1) Growth of the cells is inhibited in dose-dependant fashion by treatment with LPS in concentrations >.005 microgram/ml; (2) Doses >.1 microgram/ml induce secretion of the cytokines GM-CSF, IL-3, IL-6, and TNF, as well as inducing a marked increase in secretion of IgM, a product this line produces constitutively; (3) Treatment of the cells with amounts of LPS >1 microgram/ml rendered the cells resistant to the growth-inhibiting effects of LPS - this induced resistance was long-lasting; cells recovered from this treatment in 10-30 passage generations (about 80-240 cell divisions). Because this was the last year for this study we confined our work to confirming and elaborating a little on the latter point. We also succeeded in adapting a combination of ELISPOT and ELISABLOT assays to replica analysis of a product from the same cell. We did not succeed in quantitating the amounts secreted because of a technical problem in delivering small volumes of standards to membranes in a uniform way.