Cross-linking of VLA/CD29 molecule has a co-mitogenic effect with anti-CD3 on CD4 cell activation in serum-free culture system

In this study, we demonstrated that antibodies reactive with a common β1 subunit (CD29) of the VLA family of antigens could synergize with CD3 but not CD2 in inducing CD4 cell proliferation in a serum-free culture system. The extent of activation was similar to that obtained when CD4 cells were cultured with anti-CD3 plus fibronectin. The proliferative response induced via the CD3-CD29 pathway was associated with the interleukin (IL) 2 autocrine pathway, including IL2 production and IL2 receptor expression. Specifically, cross-linking of VLA-5, but not other members of the VLA family of antigens with the CD3 molecule induced strong CD4 cell activation. However, cross-linking of CD3 with other cell surface antigens such as CD4 did not induce CD4 cell activation in this serum-free culture system. The above results strongly suggest that the VLA/CD29 family of antigens may play an important role in regulating CD4 T cell activation via the CD3-T cell receptor pathway.