Feline polymorphonuclear neutrophils produce pro-inflammatory cytokines following exposure to Microsporum canis

The mechanisms involved in the establishment of the specific immune response against dermatophytes remain unknown. Polymorphonuclear neutrophils (PMNs) are recruited early during the infection process and participate in the elimination of dermatophytes. They could therefore be involved in the induction of the immune response during dermatophytoses by producing specific cytokines. The aim of this work was to assess the in vitro cytokine production by feline PMNs exposed to living arthroconidia from the dermatophyte species Microsporum canis or stimulated with either a secreted or a structural component of M. canis, the latter consisting of heat-killed arthroconidia. The levels of specific cytokines produced by PMNs were determined by capture ELISA and/or quantitative RT-PCR. Results showed that PMNs secrete TNFα, IL-1β and IL-8 following exposure to M. canis living arthroconidia and stimulation with both a secreted component and heat-killed arthroconidia. The level of IL-8 mRNA was also increased in PMNs stimulated with M. canis living arthroconidia. In conclusion, infective M. canis arthroconidia induce the production of pro-inflammatory cytokines by feline PMNs that can be activated either by secreted or structural fungal components. Our results suggest that these granulocytes are involved in the initiation of the immune response against M. canis.