ANTIBODIES TO DIFFERENT MEMBERS OF THE BETA-1 (CD29) INTEGRINS INDUCE HOMOTYPIC AND HETEROTYPIC CELLULAR AGGREGATION

Members of the β1 (CD29) integrin family are involved in cellular adhesion to extracellular matrix. However, there have been several reports of CD29 integrin participation in intercellular adhesion. For example, the treatment of the human T cell line Jurkat with antibodies to α4 (CD49d) causes homotypic aggregation. The present report describes the induction of aggregation of Jurkat cells by antibodies to α5 (CD49e) and to a lesser extent by antibodies to the common β1 CD29 chain of these integrins. The metabolic requirements for these aggregations are compared with that of the CD49d-induced process. The possible involvement of fibronectin in the cytoadhesion appears to be unlikely as (1) the aggregates form in the absence of plasma fibronectin; (2) antibodies to fibronectin do not inhibit the cell adhesion; and (3) exogenous fibronectin does not influence the process. One of the cognate partners involved in the CD49e-induced aggregation appears to be present on non-antibody-treated Jurkat cells as the cells are coincorporated into aggregates of anti-CD49e-stimulated cells. The adhesion does not appear to involve members of the CD2, CD3, CD4, or CD18 receptor groups. These results indicate that interaction with α4, α5 chain or the β1, chain of the CD29 integrins leads to the induction of intercellular adhesion. The possible biological significance of this process is discussed. © 1991.