Fas-FasL interaction involved in pathogenesis of ocular toxoplasmosis in mice

Ocular toxoplasmosis is a potentially blinding intraocular inflammation. Th e intent of this study was to investigate the role of Fas-FasL interaction in a murine model of acquired ocular toxoplasmosis induced by intracameral inoculation of Toxoplasma gondii. Intraocular inflammation Fas and Fast exp ression on lymphocytes and on ocular tissues, the occurrence of apoptosis, and the frequency of CD8(+) and CD4(+) T cells in the infected eyes were an alyzed in C57BL/6 (B6) mice. Susceptibility to parasite-induced intraocular inflammation was observed in Fas-deficient (B6-lpr) and FasL-deficient: (B 6-gld) mice. Inoculation of 5,000 T. gondii tachyzoites induced significant intraocular inflammation associated with increase of Fas and Fast expressi on in the inoculated eyes of wild-type B6 mice. Flow cytometry demonstrated a significant increase of Fas and Fast expression on the splenocytes from naive mice incubated in vitro with the parasite and on the splenocytes harv ested from the infected mice at day 8 after parasite inoculation. Apoptosis of inflammatory cells tend cells in ocular tissues was seen, and a greater frequency of CD8(+) than CD4(+) T cells was observed in the infected eyes, The intensity of intraocular inflammation was greater in B6-lpr and B6-gld mice than in wild-type B6 mice (P < 0.05). The results suggest that Fas-Fa sL interaction associated with apoptosis is involved in the pathogenesis of acquired ocular toxoplasmosis in mice.