CD43 DIMINISHES SUSCEPTIBILITY TO T LYMPHOCYTE-MEDIATED CYTOLYSIS

CD43 is a major membrane sialoglycoprotein expressed by cells of hemat opoietic origin. One property of CD43 is its ability to interfere with heterotypic and homotypic cellular adhesion. To determine whether CD4 3 expression can affect cell functions requiring intercellular adhesio n, we compared a CD43-positive human T cell line (CEM) and its CD43-ne gative counterpart derived by gene targeting for susceptibility to cel l-mediated lysis. CD43-negative CEM cells were more susceptible than C D43-positive cells to lysis by allospecific T cell lines derived from several donors. Induction of CD43 expression on transfected HeLa cells also imparted resistance to lectin-mediated lysis by a CD8(+) T cell clone. The effect of CD43 expression on reducing susceptibility to lys is was more pronounced in short-term cytotoxicity assays and tended to disappear as the time of contact between the effector cell and its ta rget increased. The enhanced susceptibility of CD43-negative cells to lysis was not associated with increased expression of adhesion molecul es known to mediate antigen-independent cellular adhesion. Sialic acid residues on CD43 contributed to the CD43 protective effect. These res ults suggest that either diminished CD43 expression or incomplete sial ylation may render hematopoietic cells more susceptible to T lymphocyt e-mediated cytolysis.