Monoclonal antibodies to the murine VLA-6 alpha-chain trigger homotypic lymphocyte aggregation.

Very Late Antigen-6 (VLA-6) is a laminin receptor found on T cells, macrophages and platelets and may function as an activation antigen. Here we describe that two monoclonal antibodies (mAb) targeting the VLA-6 alpha-chain are capable of inducing homotypic aggregation of murine T-cell lines (3A9 and C10 cells). 3A9 and C10 cells are of the memory phenotype (CD4+, CD8-, CD44+, CD45+) and express VLA-6 abundantly. The VLA-6-induced aggregation is temperature dependent, energy requiring, and involves the cytoskeleton. In addition, divalent cations (Ca2+ and Mg2+) are also necessary for aggregation. The VLA-6-induced aggregation is not inhibited with mAb targeting the LFA-1/ICAM-1, VLA-4/VCAM-1 and CD2/LFA-3 adhesion pairs. We conclude that VLA-6 has a broader function and can serve as an activation molecule, triggering homotypic aggregation of T-cell subsets.