Resistance and susceptibility to infection in inbred murine strains. II. Variations in the effect of treatment with thymosin fraction 5 on the release of lymphokines in vivo.

Of nine inbred murine strains sensitized intravenously with killed lyophilized Candida albicans and challenged 3 weeks later with a C. albicans filtrate, four strains were low responders and five were high responders in the in vivo release of migration inhibitory factor (MIF) and gamma interferon (IFN-gamma). An identical distribution of high- and low-responder strains occurred in response to sensitization with Mycobacterium bovis BCG and subsequent challenge with old tuberculin. Treatment of the murine strains with thymosin fraction 5 prior to sensitization and challenge had different effects: (a) the high-responder strains had a decrease in their release in vivo of the two lymphokines; (b) three of five of the low-responder strains had a striking increase in the in vivo release of MIF and IFN-gamma; and (c) one low-responder strain did not have its response altered. A parallelism existed between the capacity of a murine strain to release the two lymphokines in vivo on stimulation with C. albicans antigens and the capacity of that strain to resist intravenous infection with living C. albicans.