Role of T cells in granuloma formation induced by Rhodococcus aurantiacus is independent of their interferon-gamma production

Intravenous injection of Rhodococcus aurantiacus into mice causes granuloma tous inflammation dependent on endogenous interferon-gamma (IFN-gamma), Thi s study investigated the mechanism of granuloma formation with an adoptive transfer system in IFN-gamma knockout (IFN-gamma (-/-)) mice. IFN-gamma (-/ -) mice infected with R. aurantiacus did not develop granulomas, and high t itres of endogenous interleukin-10 (IL-10) were detected in spleen extracts at 2 weeks after infection, The adoptive transfer of splenocytes from infe cted wild-type (IFN-gamma (+/+)) mice did not restore granuloma formation, although this treatment diminished IL-10 production in IFN-gamma (-/-) mice , Adoptive transfer of splenocytes from infected IFN-gamma (-/-) mice into infected IFN-gamma (+/+) reduced granuloma formation, These results suggest that splenocytes of IFN-gamma (-/-) mice suppress granuloma formation. On the other hand, although IFN-gamma production induced by R. aurantiacus inf ection was detected in nude mice, which are deficient in T cells, granuloma formation was not induced in them, However, adoptive transfer of immune sp lenocytes from either IFN-gamma (+/+) mice or IFN-gamma (-/-) mice could in duce granuloma formation. This means that splenocytes of IFN-gamma (-/-) mi ce have the ability to both induce and suppress granuloma formation. Induct ion of granuloma is probably dependent on both T cells and IFN-gamma produc ed by non-T cells, It is suggested that the role of T cells in granuloma fo rmation is not dependent on their IFN-gamma production.