Class I alloantigen is sufficient for cytolytic T lymphocyte binding and transmembrane signaling.

Based largely on antibody blocking studies, a number of surface "accessory" molecules on effector cytolytic T lymphocytes (CTL) have been implicated as having a role in mediating CTL binding and lysis of target cells, possibly via binding to ligands on the target cell surface. Despite this, cloned allogeneic CTL were able to specifically bind cell-size, artificial membranes (pseudocytes) bearing only class I alloantigen. This binding triggered CTL degranulation, as measured by serine esterase release. Thus, class I alloantigen alone is both a necessary and sufficient ligand for specific binding and effective transmembrane signaling to occur.