Suppressive and augmentative effects of recombinant human interleukin-2 upon delayed type of hypersensitivity in the mouse.

The in vivo action of recombinant human interleukin-2 (IL-2) was investigated against the delayed type of footpad swelling to sheep red blood cells (SRBC) in B6D2F1 mice. A single intravenous injection of 1 X 10(5) of SRBC induced transient cell-mediated immunity for delayed type of hypersensitivity (DTH) which peaked four days after the immunization and diminished rapidly thereafter. IL-2 exerted both suppressive and augmentative effects, depending on the timing of its administration in relation to the immunization. Daily intraperitoneal injections of as much as 5 X 10(4) Jurkat units of IL-2 from day 0 through day 3 caused marked suppression of DTH elicited on day 4. On the other hand, three or four consecutive injections of IL-2 from day 4 or day 3 through day 6 produced potent DTH on day 7, when DTH was faint, if there was any, without IL-2 administration. Potentiation of DTH was also observed when three injections of IL-2 were given from day 7 through day 9 and the antigen was challenged on day 10. These results suggest that IL-2 acts as an immunomodulator against cell-mediated immunity to SRBC in the mouse.