The requirement for adequate co-stimulation for effective T cell activation and function in anti-chlamydial immunity was obtained with both studies in genetically engineered ICAM-1KO mice [Igietseme et al., 1999] and in vitro killing of chlamydial-infected cells by specific CTLs [Beatty & Stephens, 1994]. ICAM-1 deficiency results in delayed T cell activation, increased acute genital chlamydial infection, and high incidence of ascending infection and development of certain complications, specifically hydrosalpinx  [Igietseme et al., 1999]. Strategies to enhance co-stimulation to promote rapid Th1 activation are currently unknown but certain adjuvants could induce co-stimulatory factors as part of their general immunomodulatory functions.

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