Primary in vitro antibody formation in the rat: partial characterization and properties of an inhibitor cell present in normal spleen.

Rat spleen cells are shown to be unresponsive to sheep red cells (SRBC) in vitro under conditions in which thoracic duct lymphocytes (TDL) respond very well. By adding unresponsive spleen cells to responsive TDL cultures, the spleen cells are shown to contain an inhibitor capable of preventing the response to SRBC. The inhibitory activity is a property of live cells; it is sensitive to radiation doses as low as 100 R x rays and to mitomycin C. It can be completely removed from spleen cell suspensions by extraction with large amounts of carbonyl iron or by filtration through nylon wool columns. It is less efficiently removed by filtration through Sephades G-10 columns, and is completely resistant to the cytotoxic effects of silica. From a practical point of view, extraction of a spleen cell suspension with carbonyl iron is a useful method of obtaining fully responsive lymphocyte populations from rat spleen.