No abstract

Several lines of evidence suggest that host genetic factors controlling the immune response influence infection by Mycobacterium tuberculosis. The proinflammatory cytokine interleukin (IL)-1β and its antagonist, IL-1Ra (IL-1 receptor agonist), are strongly induced by M. tuberculosis and are encoded by polymorphic genes. The induction of both IL-1Ra mRNA and secreted protein by M. tuberculosis in IL-1Ra allele A2–positive (IL-1Ra A2+) healthy subjects was 1.9-fold higher than in IL-1Ra A2− subjects. The M. tuberculosis–induced expression of mRNA for IL-1β was higher in subjects of the IL-1β (+3953) A1+ haplotype (P = 0.04). The molar ratio of IL-1Ra/IL-1β induced by M. tuberculosis was markedly higher in IL-1Ra A2+ individuals (P < 0.05), with minor overlap between the groups, reflecting linkage between the IL-1Ra A2 and IL-1β (+3953) A2 alleles. In M. tuberculosis–stimulated peripheral blood mononuclear cells, the addition of IL-4 increased IL-1Ra secretion, whereas interferon γ increased and IL-10 decreased IL-1β production, indicative of a differential influence on the IL-1Ra/IL-1β ratio by cytokines. In a study of 114 healthy purified protein derivative–reactive subjects and 89 patients with tuberculosis, the frequency of allelic variants at two positions (−511 and +3953) in the IL-1β and IL-1Ra genes did not differ between the groups. However, the proinflammatory IL-1Ra A2−/IL-1β (+3953) A1+ haplotype was unevenly distributed, being more common in patients with tuberculous pleurisy (92%) in comparison with healthy M. tuberculosis–sensitized control subjects or patients with other disease forms (57%, P = 0.028 and 56%, P = 0.024, respectively). Furthermore, the IL-1Ra A2+ haplotype was associated with a reduced Mantoux response to purified protein derivative of M. tuberculosis: 60% of tuberculin-nonreactive patients were of this type. Thus, the polymorphism at the IL-1 locus influences the cytokine response and may be a determinant of  delayed-type hypersensitivity and disease expression in human tuberculosis.