| Abstract: | By means of polymerase chain reaction-assisted mRNA amplification, we have monitored message levels of interleukin (IL)-12 in splenic macrophages and of interferon-γ (IFN-γ), IL-4, and IL-10 in CD4+ and CD8+ T cells using Candida albicans/host combinations that result either in a T helper type-1 (Th1)-associated self-limiting infection (“healer mice”) or in a Th2-associated progressive disease (“nonhealer mice”). The timing and pattern of message detection did not differ qualitatively by the expression of IFN-γ or IL-10 mRNA in CD4+ and CD8+ cells from healer (i.e. PCA-2 into CD2F1) vs. nonhealer (i.e. CA-6 into CD2F1 or PCA-2 into DBA/2) mice. In contrast, IL-4 mRNA was uniquely expressed by CD4+ cells from nonhealer animals. IL-12p40 was readily detected in macrophages from healer mice but was detected only early in infection in mice with progressive disease. Cytokine levels were measured in sera, and antigen-driven cytokine production by CD4+ and CD8+ cells was assessed in vitro, while IFN-γ-producing cells were enumerated in CD4? CD8? cell fractions. Overall, our results showed that (i) antigen-specific secretion of IFN-γ protein in vitro by CD4+ cells occurred only in healing infection; (ii) IL-4- and IL-10-producing CD4+ cells would expand in nonhealer mice in the face of high levels of circulating IFN-γ, likely released by CD4? CD8? lymphocytes; (iii) a finely regulated IFN-γ production correlated in the healer mice with IL-12 mRNA detection, and IL-12 was required in vitro for yeast-induced development of IFN-γ-producing CD4+ cells. Although the mutually exclusive production of IL-4/IL-10 and IFN-γ by early CD4+ cells may be the major discriminative factor of cure and noncure responses in candidiasis, IL-12 rather than IFN-γ production may be an indicator of Th1 differentiation. |
