The JOVI.1 monoclonal antibody recognizes an epitope common to a large proportion of human CD4+ or CD8+ T lymphocytes that express the T cell receptor beta chain (TCRβ). Antibody JOVI-1 recognizes human Cβ1 TCR gene product and reacts with 50-75% of T cells in normal human blood. Antibody JOVI-1 is mitogenic for T cells expressing TCR Cβ1.