| Abstract: | The present report demonstrates that the naturally occurring biologic substance, platelet-derived growth factor (PDGF), substantially inhibits human natural killer (NK) cell activity. More precisely, pretreatment of peripheral blood mononuclear cells for 2 h with nanogram amounts of either partially purified PDGF or highly purified PDGF significantly inhibited peripheral blood NK cell activity (cytotoxicity) in a dose-dependent manner as measured against the NK-sensitive target, K-562. Furthermore, pretreatment of purified NK cells for 2 h with nanogram amounts of purified PDGF also resulted in a significant, dose-dependent inhibition of human NK cell activity (cytotoxicity), as mediated by positively selected, B73.1+ human NK cells sorted on a fluorescence-activated cell sorter. In addition to the inhibition of NK-mediated cytotoxicity, nanogram amounts of purified PDGF also significantly inhibited the single-cell binding of B73.1+ human NK cells to the NK-sensitive target K-562, as determined by routine single-cell-binding assays (i.e. conjugate formation). The implications of these findings are discussed. |
