Eukaryotic plasma membranes present specialized lipid microdomains involved in different functions such as adhesion, signal transduction and polarized trafficking of proteins.  These microdomains are equivalent to detergent-resistant membranes (DRMs) and are usually enriched in cholesterol and sphingolipids. In our lab it was demonstrated that DRMs in Leishmania (Viannia) braziliensis presented about 67% of total parasite glycoinositolphospholipids (GIPLs), 70% of total parasite inositol phosphorylceramide and 67% of total parasite cholesterol/ergosterol. In order to understand the role of DRMs in parasite-macrophage interaction, promastigotes from L. (V.) braziliensis were submitted to disruption of lipid microdomains by treatment with methyl-b-cyclodextrin (MbCD). Culture of promastigotes in stationary phase were washed three times in PBS and maintained in 199 medium in absence of serum for 12 hours. The parasites were then incubated with 20mM and 40mM of MbCD at room temperature for 1 hour and for control parasites the incubations were carried out in the absence of MbCD. No difference in the parasite viability was observed. By treatment of parasite with 20mM and 40mM of MbCD about 40% and 70% of cholesterol content were removed from parasites, respectively. By radioimmunoassay using monoclonal antibody SST-1, specific to L. (V.) braziliensis GIPLs, it was observed that only 19% of GIPLs remain in non-ionic detergent insoluble fractions after MbCD treatment, indicating that microdomains containing GIPLs were also disrupted by MbCD. The parasites preincubated or not with MbCD were placed in plates with peritoneal macrophages for 1 hour and the non-adherent parasites were removed by washing with medium. Infected macrophages were maintained in RPMI with 10% fetal calf serum in CO₂ incubator for 24 hours. The phagocytic index was 44.9 ± 6.4 for control parasites, 22.5 ± 2.9 and 21.3 ± 0.3 for treated parasites with 20mM and 40mM of MbCD, respectively. The disruption of lipid microdomains present in promastigotes decreased the infectivity in macrophage by 50% for parasites treated with 20mM of MbCD and 53% for parasites treated with 40mM of MbCD, indicating that membrane microdomains enriched in cholesterol and GIPLs are important to Leishmania-macrophage interaction.