SB-Specific CTL Clones Exhibit Functional Heterogeneity in their Susceptibility to Blocking by Anti-T3 and Anti-T4 Antibodies

Abstract

Human T cells which recognize class II major histocompatibility complex (MHC) antigens are almost exclusively contained within a subpopulation of T cells that bear the T4 (Leu 3) cell surface marker^1–3. Antibodies that bind the T4 molecule have been shown to block the proliferative and cytotoxic responses of T4⁺ cells to class II MHC antigens^2,3,4. Studies that have partitioned the cytolytic process into binding and post-binding phases have demonstrated that anti-T4 antibodies block cytolysis by interfering with formation of functional conjugates^6,7. These and other findings have led to the hypothesis that the function of the T4 molecule is to bind to a non-polymorphic epitope on class II molecules and to thereby act as an ancillary structure that can facilitate T cell-target cell interactions^{2, 6, 8}.