CD4-induced down-regulation of T cell adhesion to B cells is associated with localization of phosphatidyl inositol 3-kinase and LFA-1 in distinct membrane domains

We have previously shown that binding of anti-CD4 antibody inhibit LFA-1-dependent adhesion between CD4+ Tcells and B cells in a p56lck and a PI3-kinase-dependent manner. In this work, we investigated with two different T cell lines (Jurkat and A201) whether CD4 binding could alter interactions of the proteins putatively involved in this adhesion regulatory pathway. Anti-CD4 binding was shown to induce a transient association between PI3-kinase and LFA-1, which took place in different regions of the plasma membrane. It was detected in detergent soluble membrane but also in detergent insoluble membrane consisting in raft microdomains, composed of GM1 and/or GM3 gangliosides. These results show that anti-CD4 Ab could modify the interaction between LFA-1 and signaling molecules, such as PI3-kinase and induce, in part, their recruitment in raft domains. By using specific inhibitors, raft integrity and CD4 association with GM3 were found necessary for observing the CD4-dependent inhibition of LFA-1-mediated adhesion. These results strongly suggest that these molecular rearrangements in the membrane are necessary to induce down-regulation of LFA-1-mediated adhesion. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA.