The influence of T cell receptor and cytokine genes on sarcoidosis susceptibility in African Americans

Abstract

The pathogenesis of sarcoidosis, a multisystem granulomatous disorder, is mediated through immunoregulatory pathways. While sarcoidosis clusters in families, inherited risk factors remain undefined. In search of possible sarcoidosis susceptibility genes, we examined anonymous polymorphic genetic markers tightly linked to six different candidate gene regions on chromosomes 2q13, 5q31, 6p23-25, 7p14-15, 14q11 and 22q11. These candidate regions contain T cell receptor, interleukin (IL) and interferon regulatory factor (IRF) genes. Our study population consisted of 105 African-American sarcoidosis cases and 95 unrelated healthy controls. The allelic frequency distribution of two out of the six markers, IL-1 alpha marker (p = 0.010) on 2q13 and the F13A marker (p = 0.0006) on 6p23-25, was statistically significantly different in cases compared with controls. The two alleles most strongly associated with sarcoidosis were IL-1 alpha*137 (Odds Ratio (OR) = 2.60; 95% confidence interval (CI) = 1.36-4.98) and F13A*188 (OR = 2.42; 95% CI = 1.37-4.30). Individuals that had both of these alleles were at a six-fold increased risk for sarcoidosis (OR = 6.19; 95% CI = 2.54-15.10). Restricting the analysis to cases with at least one first or second-degree relative affected with sarcoidosis increased the OR to 15.38. IL-1 levels are elevated in sarcoidosis and the F13A marker is tightly linked to a gene that codes for a newly identified interferon regulatory factor protein (IRF-4), which is thought to play a role in T cell effector functions. Our results suggest genetic susceptibility to sarcoidosis may be conferred by more than one immune-related gene that act synergistically on disease risk.