Expansion of gamma interferon-producing CD8+ T cells following secondary infection of mice immune to Leishmania major.

Reinfection of immune mice with Leishmania major elicits a secondary gamma interferon (IFN-gamma) response to which specific CD8+ T cells are essential. We have shown previously that specific CD8+ T cells from reinfected immune mice release substantially higher levels of IFN-gamma, a cytokine essential for the efficient activation of parasitized macrophages to kill intracellular L. major. By using an ELISPOT assay, which allows the detection of IFN-gamma production by individual cells, it is shown here that this elevated IFN-gamma response is the result of an increase of up to 50-fold in the frequency of parasite-specific CD8+ T lymphocytes in the spleens and draining lymph nodes of both immune reinfected CBA and BALB/c mice. This observation is additional evidence of the role that CD8+ T cells play in immunity to reinfection with L. major.