RESUMO
Abstract Among the microorganisms that make up the intestinal microbiota, stands out Escherichia coli, which has as main ecological niche, the large human intestine. Its importance stands out in being part of the pioneer's commensal microorganisms on the colonization of the intestinal mucosa and its pathogenic role causing extra and intra intestinal diseases. The aim of the study was to evaluate the antibody production and proliferative response of Peripheral Blood Mononuclear Cells (PBMC) to E. coli antigens. The bacteria were grown on Brain Heart Infusion broth medium at 35 ºC for 72 hours. Pellet bacteria were lysed for one hour at room temperature with an 8M sodium guanidine solution. After spin and dialysis, the protein antigens were measured in the supernatant by protein assay. The antigens were characterized by polyacrylamide gel electrophoresis and the antigenic profile by western blotting. The presence of specific IgG and IgA antibodies were evaluated using thirty normal human sera by an indirect ELISA. The response of PBMC to E. coli antigens was assessed by MTT metabolization. The results demonstrated that the antigens were composed of proteins of different sizes and they were recognized by antibodies present in normal human serum. Human sera presented high titers of IgG and IgA antibodies to E. coli antigens when compared to the results of lipopolysaccharide. We also showed that total E. coli antigens induced PBMC proliferation at different antigen concentrations. Taken together the results suggest that the antigens from E. coli can induce local and systemic immune responses.