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Background:The primary work-related lung disease in Brazil is silicosis. Its pathogenic agent is the dust of crystalline free silica (SiO 2 ; silicon dioxide). The inflammatory process of silicosis is not yet well understood.Objective: To analyze, through immunologic laboratory evaluation, including nonspecific and specific immunity, the profile of IgG, IgM, IgA, C3, C4 and autoantibodies in the serum of workers, with or without silicosis, exposed to silica.Methods: Fifty-eight male workers were studied. All had been exposed to silica. Immunologic, radiologic and functional evaluations were made. The immunoglobulins IgG, IgA, and IgM, the complement system components C3 and C4, and the autoantibodies were assessed.Results: Chest X-rays were normal in 20 of the 58 workers and compatible with silicosis in 38. Among the 38 who were positive, IgG values were, on average, higher than in the group with normal X-rays (p < 0.05). There were no significant differences in average values of IgA, IgM, C3 or C4 (p > 0.05). The percentage of autoantibody positivity was higher in the silicosis group than in the group with normal X-rays. Conclusion:The increased levels of IgG in patients with silicosis constitutes an important discovery. It may represent continuity of the granulomatous reaction, even when the individual is no longer being exposed to silica. However, further studies are necessary in order to increase understanding of the mechanism involved in the silicosis immunologic process.

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