Immunologically specific production of interferon in cultures of rabbit blood lymphocytes: association with in vitro tests for cell-mediated immunity.

Lymphocytes of animals with delayed hypersensitivity produce mediators of cellular immunity when challenged in vitro with specific antigen. Among these are macrophage migration inhibitory factor (MIF) and interferon (IF). Nonspecific mitogens also induce the production of these lymphokines. In the following study leukocytes and column-purified lymphocytes of the same peripheral blood sample from tuberculin (purified protein derivatives [PPD])-sensitive rabbits were concurrently cultured in medium alone or with PPD. Supernatants of 1- and 4-day lymphocyte cultures were assayed for MIF. Supernatants of 1-, 2- to 4- and 5- to 7-day leukocyte cultures were assayed for IF by inhibition of cytopathic effect of vesicular stomatitis virus on rabbit kidney cultures. In the presence of PPD, normal lymphocytes did not produce MIF, but lymphocytes from sensitized animals did (8/8 animals), after 1 and 4 days of culture. Leukocytes from normal animals produced little or no IF when cultured with or without PPD. Leukocytes from sensitized animals cultured in medium alone produced little IF. However, when cultured with PPD they produced significant amounts of IF on day-1 (6/8 animals) and day-2 to day-4 (4/8) animals. There was no correlation between relative amounts of MIF and IF produced by cultures of respective cells from individual animals. Rabbit IF produced or released in vitro appeared in significant and maximum amounts by 24 h coincident with the time release of significant amounts of another mediator of cellular immunity, MIF.