Activated polymorphonuclear leukocytes affect red blood cell aggregability.

Activated leukocytes can affect adjacent cells by generating oxygen free radicals and secreting proteolytic enzymes, and red blood cells (RBC) exposed to such agents should be susceptible to their effects. This study was thus designed to investigate the effects of activated polymorphonuclear leukocytes (PMN) on RBC aggregability (i.e., on intrinsic RBC aggregation characteristics). PMN were isolated from human blood by density separation and suspended in glucose-enriched buffer with RBC isolated from the same blood sample (RBC/PMN ratio of 150:1). PMN were then activated in this suspension by adding 1 ng/mL tumor necrosis factor alpha (TNF-alpha) and 10(-7) M N-formyl-methionyl-leucyl-phenylalanine (fMLP) or fMLP alone. After incubation for 2 h at 37 degrees C, RBC aggregation behavior in autologous plasma was assessed; RBC deformability and partition coefficients were also measured. RBC aggregation was significantly increased after incubation and deformability and partitioning were decreased; these effects were prevented by phenylmethylsulfonyl fluoride (1 mM) or superoxide dismutase (20 microg/mL) plus catalase (40 microg/mL). TNF-alpha and fMLP alone had no effect on RBC aggregation if PMN were not present. Activated PMN can thus markedly affect RBC aggregability, apparently via both proteolytic enzymes and oxygen free radicals; enhanced aggregation seen in clinical states associated with PMN activation or observed during in vivo RBC aging may also involve such PMN-RBC interactions.