Control of lymphocyte integrin function: evidence for multiple contributing factors.

The control of lymphocyte adhesion is critical for proper cellular functions. The alpha 2 beta 1 integrin complex serves as a receptor for collagen on lymphocytes. The T cell leukemia Jurkat expresses alpha 2 beta 1 in a latent form on the cell surface. Three types of stimuli, antibody to the alpha 2 chain (JBS2), antibody to the beta 1 chain (JB1B), and phorbol ester (PMA), each induce activation of alpha 2 beta 1-dependent Jurkat binding to collagen. A comparison of the JBS2, JB1B, and PMA induction requirements indicated that the JB1B and the JBS2 effects are not sensitive to staurosporine while the PMA response is completely inhibited. Combinations of functionally saturating concentrations of the stimuli displayed an additive effect. Collectively these results suggest that several factors contribute to the generation of full integrin functionality and cellular adhesion, thus providing a possible basis for incrementally controlling the adhesive potential of lymphoid cells.