Homotypic aggregation of CD103 (alpha E beta 7)+ lymphocytes by an anti-CD103 antibody, HML-4.

One monoclonal antibody, HML-4, directed against the alpha E beta 7 integrin (CD103), an integrin preferentially expressed on human intestinal intraepithelial lymphocytes (IEL), induced the homotypic aggregation of IEL and of a CD103+ MOLT16 cell line. Aggregation was an active adhesion event dependent on an intact cytoskeleton, on tyrosine phosphorylation but not on activation of protein kinase C. It was blocked by four other anti-CD103 antibodies but by none of the antibodies blocking known adhesion lymphocyte pathways.