Interleukin 2 production by a marmoset B cell Iine

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Abstract
Several B cell lines constitutively secreting interleukin (IL) 2 were derived from the Epstein‐Barr virus‐positive marmoset B cell line, B95–8. A representative line, KRC‐18, was cloned by limiting dilution and found to be 40% surface IgM+, 60% cytoplasmic IgM+, > 95% DR+, weakly Tac+ and devoid of T cell, monocyte and NK cell surface antigens. Supernatant from KRC‐18 cells supported the long‐term growth of an IL 2‐dependent murine T cell linc, HT‐2, and contained 7—8 units/ml of IL 2 activity when compared to recombinant IL 2. The supernatant was fractionated by Sephadex G‐75 gel filtration, and maximal proliferation of HT‐2 cells was supported by the 20—22‐kDa column fraction. The proliferative response of HT‐2 cellsto KRC‐18 supernatant was inhibited by monoclonal antibodies to human IL 2 or the murine IL 2 receptor in a dose‐dependent manner, suggesting that the KRC‐18IL 2 has epitopes that are similar to human IL 2, and that its activity is mediated through binding to the IL 2 receptor of the target cell line. When KRC‐18 cells were analyzed for cytoplasmic IL 2, >90% of the cells contained intracellular IL 2 in amountsequivalent to, or greater than, mitogen‐activated T cells. These data indicate that certain B lineage cell lines are capable of IL 2 synthesis and secretion.