Fcgamma and complement receptors: expression, role and co-operation in mediating the oxidative burst and degranulation of neutrophils of Brazilian systemic lupus erythematosus patients

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Abstract
We have investigated the individual role of FcgR and CR, as well as their cooperation, in mediating the oxidative burst and degranulation of neutrophils of Brazilian systemic lupus erythematosus (SLE) patients. Neutrophils were stimulated with the immune complexes (IC)-IgG or-F(ab')2, opsonized or not with normal or SLE human serum. The oxidative burst was decreased in neutrophils of active SLE patients compared to healthy controls when this response was mediated by FcgR and/or CR, while the degranulation was unaffected. The SLE hypocomplementemia did not affect the oxidative burst mediated only by CR. FcgRII and CR1 expression on neutrophils of active SLE patients was reduced, while the expression of FcgRIII and CR3 was unaffected. These results suggest that the different FcgR and CR may be involved or cooperate in different ways in the mediation of the oxidative burst and the degranulation. Moreover, the decreased oxidative burst of neutrophils of active SLE patients may not depend only on SLE hypocomplementemia for IC opsonization. These observations are directed at the understanding of how each of these immune system components (FcgR, CR and complement) influences the precise biological neutrophil responses both in physiological and pathological conditions. Since the Brazilian population comprises many races, these results are important because they are directed at a specific population of SLE patients.