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Interleukin 2 production by a marmoset B cell line
L H Brent1, T Miyawaki, M P Everson
1Department of Pediatrics, University of Alabama, Birmingham.
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+, greater than 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 line, 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 cells to 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-18 IL 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, greater than 90% of the cells contained intracellular IL 2 in amounts equivalent 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.
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+, greater than 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 line, 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 cells to 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-18 IL 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, greater than 90% of the cells contained intracellular IL 2 in amounts equivalent 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.