Exceptional Lymphocyte Stimulating Capacity of Cells from Lymphoid Cell Lines

Abstract

WE recently reported that X-irradiated lymphoid cells from a Burkitt lymphoma cell line are exceptionally potent activators of normal human lymphocytes¹. The reaction appears to resemble the much less intense lymphocyte activation which occurs when lymphocytes from two donors are mixed in culture—the so-called mixed lymphocyte reaction or MLR². Evidence suggesting that the intensity of the MLR is correlated with the genetic disparity of the cell donors (see ref. 2) has led to the view that the reaction is mediated solely by foreign antigens on the cell. Although little work has been done, lymphocytes do not appear to have an “inbuilt” reactivity towards all foreign cellular antigens because they are not activated by foreign red cells¹, thyroid cells, kidney cells³ or X-irradiated HeLa cells¹. To try to define the nature of the high level of activation occurring when normal human lymphocytes are mixed with X-irradiated lymphoma cells we have examined the effect of mixing lymphocytes with irradiated cells from various other human lymphoid cell lines (LCLs), some of which contain a herpes-like virus (Table 1). Two further LCLs of lymphoma origin were provided by Professor M. A. Epstein⁴, four initiated from normal human donors by Dr P. Gerber⁵ and a number from normal individuals and patients with various diseases by Professor G. Moore⁶. A marked activation occurred in all mixtures tested (Table 1). Experiments were designed to answer three questions.