Characterization of CD28, CTLA4, and ICOS polymorphisms in three Brazilian ethnic groups

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Guzman, V. B.
Morgun, A.
Shulzhenko, N.
Mine, K. L.
Goncalves-Primo, A.
Musatti, C. C.
Gerbase-Delima, M.
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Costimulatory molecules CD28, CTLA-4 (cytotoxic T-lymphocyte-associated antigen-4), and ICOS (inducible costimulator) genes lie within the 300-kb chromosome region 2q33. CD28, CTLA-4, and ICOS have been described to be important regulators of T-cell activation. With the objective to Study ethnic variations in allelic frequencies and linkage disequilibrium (LD) patterns, we genotyped CD28 intron 3 (+17 T > C), CTLA4 promoter (-319 C > T), CTLA4 exon 1 (+49 A > G), and ICOS 3' UTR (1564 T > C) polymorphisms in white (n = 103), mulatto (n = 97), and black (n = 79) Brazilian healthy individuals. No significant deviations from Hardy-Weinberg equilibrium were found in any of the population samples. A higher frequency of CD28 +17 C allele was detected in white (27%) in comparison with mulatto (15%) and black (13%) (p = 0.005) populations. LD between CD28 +17 C and CTLA4 -319 T alleles was observed in whites (p < 0.0001), mulattos (p = 0.0001), and blacks (p = 0.0002).
Human Immunology. New York: Elsevier B.V., v. 66, n. 7, p. 773-776, 2005.