Contribution of 65-kDa heat shock protein induced by gamma and delta T cells to protection against Toxoplasma gondii infection.

Heat shock proteins (HSPs) are evolutionarily highly conserved polypeptides synthesized by many cells to preserve cellular functions under a variety of stressful conditions including infections. We have investigated the involvement of 65-kDa HSP (HSP65) in host protection against an intracellular protozoan parasite, Toxoplasma gondii, in mice. Experiments using low and highly virulent strains of Tox. gondii revealed that induction of murine HSP65 on macrophages closely correlates with protection against infection with this protozoan. Furthermore, we clarified that T cells, especially gamma delta T cells, are indispensable for HSP65 expression. A similar relationship between the expression of HSP65 on host macrophages and protective immunity was observed in mice infected with Leishmania major and Trypanosoma cruzi, both of which are obligate intracellular protozoa as is Tox. gondii.