Enhancement of human NK and LAK cytotoxicity against HCMV-infected cells by rhamnogalacturonan: specificity of reaction.

Human peripheral blood mononuclear cells (PBMC) and their subpopulations obtained from healthy donors were used to study improvement of MHC-unrestricted cytotoxic reactions against cells infected with human cytomegalovirus (HCMV) at different multiplicities of infection. Natural killer (NK) and lymphokine-activated killer (LAK) cytotoxicity against HCMV-infected cells was greatly enhanced in the presence of rhamnogalacturonan (500 ng/ml). The increase of the multiplicity of infection from MOI 0.1 to 1.0 had only a slight effect on cytotoxicity enhancement by rhamnogalacturonan. The chemical specificity of interaction of rhamnogalacturonan with effector cells and virus-infected cells was found to be analogous to the interaction with tumor cells, i.e., both types of target cells must express a receptor for rhamnogalacturonan since rhamnogalacturonan-mediated enhancement of NK and LAK cytotoxicity against HCMV-infected cells was similarly inhibited by preincubation of CD56+ effector cells with 60% deacetylated D-mannose pentaacetate.