Acute poststreptococcal glomerulonephritis (APSGN) is a consequence of the immune response to streptococcal antigens with further in situ antigen-antibody interaction and deposition of circulating immune complexes, resulting in the activation of complement and the inflammatory process. These events are related to a previous antibody response. However, early renal events, when circulating streptococcal antigens bind to the kidney during streptococcal infection, remain unknown. Cationic streptococcal erythrogenic toxin type B (ETB) and its precursor (ETBP) are largely produced by nephritogenic streptococci and have high affinity for anionic glomerular structures. Renal deposition of ETB/ETBP makes conceivable a possible interaction between these streptococcal proteins with intrinsic glomerular cells or infiltrating leukocytes. Since ETB/ETBP are chemotactic for leukocytes and capable of inducing proliferation, cytokine and chemokine production, expression of adhesion molecules and apoptosis in renal cells and leukocytes, the early presence of these proteins could be a relevant event before and during antigen-antibody interaction takes place in renal tissues.