HLA Class I, II, and III Polymorphism in Italian Patients With Sarcoidosis

HLA Class I, II, and III Polymorphism in Italian Patients With SarcoidosisSarcoidosis is a multisystem granulomatous disorder characterized by an accumulation of immunocompetent cells at sites of disease activity. Though the etiology is unknown, both prevalence of sarcoidosis in different ethnic groups and familial occurrence of the disease strongly put forward the hypothesis of a possible genetic predisposition.
Frequencies of human leukocyte antigens (HLA) coded by genes of the HLA region in patients with sarcoidosis have been studied by many investigators in order to understand the role of immunogenetic factors in the pathogenesis of this disease. Despite the relatively large body of published articles, a final conclusion on the association of sarcoidosis and HLA has not been reached. Conflicting results were achieved when different ethnic groups were considered, so that, for instance, from pooled data an association between HLA and sarcoidosis in Caucasians has been denied. When another ethnic group or narrower caucasian groups were considered, the existence of association between sarcoidosis and certain HLA alleles, especially B8 in Caucasians, has been recognized. This implies the presence of a putative sarcoidosis-susceptibility gene within or linked to the HLA region.
Several studies have indicated that most conditions with autoimmune component are associated with particular HLA profiles. This fact leads to the hypothesis that, like autoimmune diseases, sarcoidosis may be associated with a discrete HLA pattern. Clinical heterogeneity of this disease might be determined by multiple interactions of different factors (hormonal, environmental, humoral, and genetic) which, combined in different subjects in various ways, induce distinct forms of disease.
The aim of this investigation was to perform an immunogenetic study of sarcoidosis in Italians, a population with an annual average incidence of sarcoidosis estimated as 0.5/100,000 inhabitants. So far, to our knowledge, Italian patients with sarcoid have not yet been studied for HLA. Furthermore, we believe that this is the first report of a study of C4A, C4B, BF complement proteins (coded by major histocompatibility complex [MHC] class III genes) in sarcoidosis. In this article, we present the results obtained in a large series of patients in which age of onset, radiologic stage, extrathoracic spread, and sex of patients have been considered in order to assess whether there was a specific relationship with particular HLA markers.

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