Although no relevant changes were noticed with capacitation, modifications in the immunofluorescence pattern of some proteins were observed in acrosome-reacted sperm. The acrosome reaction involves an extensive reorganization of the membranes located in the anterior head of the sperm cell. Multiple fusion points between the plasma and outer acrosomal membranes induce a fenestration process during which the components originally located in the apical portion of the sperm are lost [1] . After fusion, the inner acrosomal and plasma membranes become continuous, assembling a new sperm surface resulting from the mixing of their respective components. Caveolin 2, originally found in the anterior head of the sperm, could not be detected after the acrosome reaction, suggesting that this antigen is likely located at the plasma membrane covering the acrosomal cap and is consequently lost during exocytosis. In the case of GM3, although no signal was found on reacted sperm, the original localization of this ganglioside did not predict this behavior because the equatorial segment is excluded from the vesiculization process that takes place during the acrosome reaction [1] . Although the possible loss of GM3 cannot be ruled out, considering that anti-GM3 recognizes the glycoside portion of the GM3 molecule [42] , the lack of signal of acrosome-reacted sperm could also be due to the removal of the respective epitope by acrosomal glycosidases released during exocytosis [1] .