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David C. Reed, Gary N. Holland, Patrick A. Coady, Ralph D. Levinson, Michael E. Zegans, Tiago E. Arantes, Jose G. Montoya, Ying Qian, Raj Rajalingam, North American Ocular Toxoplasmosis Research Group; An Association between Killer Cell Immunoglobulin-like Receptor (KIR) Genes and Toxoplasmic Retinochoroiditis. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2396.
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© ARVO (1962-2015); The Authors (2016-present)
Killer cell immunoglobulin-like receptor (KIR) genes control the effector function of natural killer cells, a subset of lymphocytes that are involved in the early immune response against Toxoplasma gondii infection. KIR genes, which are polymorphic and polygenic, are classified into activating and inhibitory types. We sought relationships between toxoplasmic retinochoroiditis and KIR genes.
We characterized the presence or absence of 14 distinct KIR genes and 2 pseudogenes of 33 immunocompetent Hispanic and white Caucasian adults with serologic evidence of T. gondii infection. All subjects underwent ophthalmic examination to determine the presence of toxoplasmic retinochoroiditis. KIR genotypes were compared to those of 250 healthy Caucasian controls.
Ocular involvement was present in 26 individuals (78.8%). The frequency of activating gene KIR2DS3 was increased in patients with ocular involvement (14 [53.8%] of 26 individuals) when compared to healthy controls (55 [28.2%] of 195 controls, p=0.012). There was also a weak association of the activating gene cluster KIR2DS2-2DL2-2DS3-2DL5 when patients with ocular involvement (11 [42.3%] of 26 individuals) were compared to healthy controls (47 [24.1%] of 250 controls, p=0.058). Similar associations were seen among T. gondii-infected individuals when those with ocular involvement were compared to those without ocular involvement, although numbers were small and statistical significance was not confirmed. KIR2DS3 was more common in those with ocular involvement (14 [53.8%] of 26 individuals) than in those without ocular involvement (1 [14.3%] of 7, p=0.095). The gene cluster KIR2DS2-2DL2-2DS3-2DL5 was more common in those with ocular involvement (11 [42.3%] of 26 individuals) than in those without ocular involvement (1 [14.3%] of 7 individuals, p=0.22).
Our data suggest the possibility that development of clinically apparent toxoplasmic retinochoroiditis may be related, in part, to a heightened inflammatory reaction mediated by activating KIR gene products.
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