Soluble immune responses suppressor (SIRS) is a protein produced by activated suppressor T lymphocytes which inhibits division by tumor cells and plaque-forming cell (PFC) responses in vitro. Although this lymphokine has been fairly well characterized in vitro, little is known about its effects in vivo. Purified murine SIRS, 103 to 104 U injected i.p., suppressed murine PFC responses to sheep erythrocytes (SRBC) in vivo. Suppression occurred when SIRS was injected into mice 5 days before assay, and also occurred when SIRS activated with 10-6 M H2O2 was injected 24 hr before assay. These kinetics are similar to those observed in tissue culture, where supression of PFC responses requires the addition of SIRS 4 to 5 days before assay unless SIRS is activated to SIRS(ox) by H2O2. Levamisole, an inhibitor of SIRS-mediated supression in vitro, also blocked suppression by SIRS in vivo. Delayed-type hypersensitivity reaction to footpad injection of SRBC was also inhibited by SIRS. Suppression of PFC responses by recombinant immune interferon (IFN-γ), which activates lymphocytes to produce SIRS in vitro, was blocked by injection of levamisole or monoclonal anti-SIRS antibodies. These results show that SIRS suppresses immune responses in vivo, and suggest that suppression of PFC responses by IFN-γ may be largely mediated by SIRS. These findings indicate that SIRS could contribute to the development of suppressed immunity in vivo.
|Original language||English (US)|
|Number of pages||5|
|Journal||Journal of Immunology|
|State||Published - 1986|
ASJC Scopus subject areas
- Immunology and Allergy