Very early (VEA) and very late (VLA) activation antigens have distinct functions in T lymphocyte activation.

We have described in detail the properties of two types of murine T-cell activation antigen. mAbs to these cell surface antigens were initially identified because they demonstrated apparent selective reactivity with a number of cloned cell lines derived from dendritic epidermal T cells. After careful study, both of these antigens were also found to be expressed by normal T cells. The dimer recognized by mAb H1.2F3 which we have termed Very Early Activation (VEA) antigen, is rapidly and transiently expressed during the process of normal T-cell activation. It is likely that the VEA antigen plays a major role in T-cell activation as mAb H1.2F3 is a potent stimulator of T-cell proliferation in the presence of PMA and accessory cells. The second cell surface antigen recognized by mAbs H9.2B8 and 8.18E12 is a Very Late Activation (VLA) antigen that has biochemical, tissue distribution, and functional properties which resemble the human VLA antigens, which have been recently shown to be members of the integrin superfamily of cell surface receptors. While the physiologic ligand for the VEA antigen has yet to be identified, the integrin identified by mAbs H9.2B8 and 8.18E12 mediates cell adhesion to a well-defined group of ligands consisting of the ECM-proteins fibronectin, fibrinogen, and vitronectin. We postulate that the VEA and VLA antigens have distinctly different functions and that further detailed analysis of these dimers will further elucidate the role of these cell surface antigens in T-cell activation and function.