Use of the monoclonal antibody 12F1 to characterize the differentiation antigen VLA-2

Abstract

A monoclonal antibody, 12F1, has been produced that specifically immunoprecipitates the human cell surface structure VLA-2 from platelets and long-term activated T cells, as well as from fibroblast and neuroblastoma cell lines. Cross-linking studies indicate that the VLA-2 structure exists on the cell surface as a 165,000 Mr heavy chain (alpha 2) in noncovalent 1:1 association with a 130,000 Mr light chain (beta). The monoclonal antibody A-1A5, which reacts with the beta subunit common to all VLA structures, was able to completely preclear VLA-2, indicating that all of the alpha 2 subunit was associated with VLA beta-chain. The specificity of 12F1 for VLA-2 allowed independent immunoprecipitation and flow cytometry analysis of this alpha 2 beta structure separate from any other VLA structures that may have been present such as VLA-1 or free beta-subunit. Subunit dissociation studies were used to demonstrate that 12F1 recognizes an epitope on the alpha 2 chain on VLA-2, which is consistent with the 12F1 specificity for VLA-2 alone among the VLA proteins. Analysis of activated T cells indicated that VLA-2, like VLA-1, is another "very late" appearing T cell activation antigen that arises concurrently with VLA-1 starting at day 7 and increasing through 2 wk. VLA-2 was found on many of the same cells as VLA-1 (inactivated T cells, T cell leukemia cells, fibroblasts, SK-N-SH neuroblastoma cells), but VLA-1 and VLA-2 can be expressed independently, because VLA-2 was also present on VLA-1-negative cells such as HSB and platelets, and VLA-1 was present on VLA-2-negative C8215 cells.