An immunoregulatory role for neutrophils in CD4+ T helper subset selection in mice with candidiasis

Granulocytes may serve immunoregulatory and effector roles in different limbs of the immune response to infection. Using live vaccine strain or virulent challenge in mucosal or systemic infection of mice with Candida albicans, we examined the effect of mAb-mediated depletion of neutrophils on the course of primary and secondary challenge and on development of CD4+ cell-dependent immunity. We obtained evidence of deleterious effects of neutrophil depletion occurring at the time of infection under all conditions of testing, both in naive and in previously immunized mice. In contrast, neutrophil depletion appeared to benefit the hosts late in the course of an overwhelming systemic infection. In an attempt to correlate neutrophil function with the nature of the T cell response, we tested the ability of neutrophils to produce cytokines associated with functionally distinct CD4+ Th cell responses to Candida. We found that neutrophils were endowed with the capacity to secrete IL-12 and IL-10 in vitro in response to the yeast. Neutrophil ablation early in the course of Th1-associated, self-limiting infection appeared to change the qualitative development of the T cell response, and rendered mice susceptible to infection. In addition to long recognized contributions to acute anti-candidal responses, these data suggest an important role for neutrophils both in initiation and in expression of Candida-specific immunity.