Studies on tissue factor activity and production by leukocytes of human umbilical cord and adult origin

Human adult and umbilical cord-derived leukocytes were shown to be capable of generating tissue factor activity on exposure to endotoxin and to reduced pH. Blood for leukocyte separation was collected from normal adults and from newly delivered sections of umbilical cord and mixed leukocyte preparations were obtained by separation over methyl cellulose Hypaque. The coagulant activity of the cell suspension was assayed using a one-stage or two-stage method. Cord-derived leukocytes were shown to develop greater coagulant activity than adult-derived leukocytes when stimulated by endotoxin in vitro at 2,000 cells/mm-3. This response to endotoxin was partially inhibited by prior exposure of the cells to prostaglandin (PG) E1 an to L-epinephrine. Acetylcholine stimulated the production of coagulant activity in the absence of endotoxin. Both cord and adult-derived leukocytes (20,000/mm-3) developed coagulant activity when exposed to pH reduction by lactic or hydrochloric acids and this activity was shown to be tissue factor.