A. Mencacci et al., Interleukin 18 restores defective Th1 immunity to Candida albicans in caspase 1-deficient mice, INFEC IMMUN, 68(9), 2000, pp. 5126-5131
Caspase 1, formerly designated interleukin 1 beta (IL-1 beta)-converting en
zyme, processes pro-IL-1 beta and pro-IL-18 to yield active cytokines that
play a pivotal role in inflammation and cell activation. We show here the e
ffect of caspase 1 deficiency on the inflammatory and adaptive immune respo
nses to the fungus Candida albicans. Caspase 1 deficiency did not affect su
sceptibility to primary systemic infection with the fungus, as revealed by
survival and fungal growth. However, Th1-mediated resistance to reinfection
was greatly impaired in caspase 1-deficient mice, and this correlated with
low-level production of IL-12 and gamma interferon. Early in infection, pr
oduction of these cytokines and that of tumor necrosis factor alpha, IL-6,
and, interestingly, IL-1 beta occurred normally in caspase 1-deficient mice
, while that of IL-18 was severely impaired. Exogenous administration of IL
-18, more than IL-12, restored the Th1-mediated resistance to the infection
. We conclude that, while caspase 1 is not indispensable for release of mat
ure IL-1 beta in candidiasis, the caspase 1-dependent production of IL-18 m
ay represent an important and novel pathway for the expression of sustained
Th1 reactivity to the fungus.