Our findings pointed out that the major glycoprotein recognized by ALL was able to costimulate the production of cytokines; A. leucocarpus lectin binds two glycoproteins situated in lipid raft microdomains from activated CD4+ T cells; one of which showed identity to a moesin-like protein that was visualised on activated-CD4+ T cell surface; and that anti-moesin antibody was able to costimulate CD4+ T cells activated by CD3. This evidence concerns the gene MSN and acute lymphoblastic leukemia.