Locomotor responses of human CD45 lymphocyte subsets: preferential locomotion of CD45RO+ lymphocytes in response to attractants and mitogens.

The CD45RO+ population of lymphocytes from human blood contains a higher proportion of locomotor cells than the CD45RA+ population. Direct from blood there were few locomotor lymphocytes (< 15%), but, among these, a higher proportion of CD45RO+ than of CD45RA+ cells responded to the chemotactic stimuli, foetal calf serum (FCS) and interleukin-2 (IL-2) in polarization assays. Likewise, after overnight culture, a higher proportion of CD45RO+ cells responded to IL-8. Culture for 24-72 hr in activators such as anti-CD3, purified protein derivative (PPD), phytohaemagglutinin (PHA), concanavalin A (Con A), pokeweed mitogen (PWM) or in an allogeneic mixed leucocyte reaction (AMLR) increased the proportion of locomotor lymphocytes to 20-60%, and the CD45RO+ subset showed proportionately more polarized cells than the CD45RA+ subset after culture with all the above activators. Preferential migration of CD45RO+ cells into collagen gels was also seen after culture in antigenic stimuli (PPD or AMLR) but not with polyclonal activators (alpha CD3 or Con A). Double labelling showed that, within the CD4+ and CD8+ subsets, antigen-stimulated CD45RO+ T cells invaded collagen gels in higher proportions than CD45RA+ T cells. Clustering of lymphocytes with accessory cells is an essential prerequisite for locomotion and, after culture in alpha CD3, CD45RO+ lymphocytes were found preferentially in clusters with monocytes. In all of the above populations, CD45RO+ lymphocytes were larger in size. These findings suggest that, not only selective adhesion to vascular endothelium as reported earlier, but also selective locomotion recruits CD45RO+ lymphocytes into sites of inflammation.