Both viable and killed Candida albicans cells induce in vitro production of TNF-alpha and IFN-gamma in murine cells through a TLR2-dependent signalling

The in vitro production of TNF-alpha and IFN-gamma in response to Candida albicans was investigated in wild type, TLR2-/- and TLR4-/- murine cells. TLR2-/- resident peritoneal macrophages showed a strong impairment of TNF-alpha production in response to viable and non-viable (heat-killed, antimycotic-treated and formaldehyde-fixed) yeasts and hyphae (germ tube-bearing cells) of the high virulence C. albicans ATCC 26555 strain, as compared with macrophages from wild-type and TLR4-/- mice. The in vitro production of IFN-gamma was investigated in murine splenocytes obtained three days after intravenous injection with the low virulence, non-germinative C. albicans PCA2 strain, and again, TLR2-/- splenocytes showed a strong impairment of the in vitro production of IFN-gamma in response to non-viable (heat-killed, antimycotic-treated and formaldehyde-fixed) C. albicans ATCC 26555 yeasts, as compared with splenocytes of TLR4-/- and wild type mice. These results indicate that the TLR2-mediated recognition of C. albicans leading to a proinflammatory Th1 host response appears to be well conserved in killed C. albicans cells, regardless of the inactivating treatment employed.