Transcutaneous leukocyte migration in vivo: cellular kinetics, platelet and C5a dependent activity

A simple quantitative method for the measurement of leukotaxis in vivo is described. Duplicate skin chambers are placed over tape-stripped skin with 50% autologous serum--50% Hank's balanced salt solution as the attractant. Neutrophils predominate throughout 24 hr in this method with no change to mononuclear cells. A recommended modification of our original method is that chambers are sampled and removed after 8 hr rather than 24 hr since the majority of leukocyte migration occurs within the first 8 hr. Analysis of serum factors showed that heat-inactivation of the serum (56degreesC for 30 min) had no effect. However, depleting platelets or C5 from the serum removed approximately 90% of chemotactic activity for human neutrophils in vivo. Platelets, presumably through activity of their granules, enzymatically cleaves C5a from C5 in plasma. We conclude that C5a, after cleavage from C5, accounts for the majority of chemattractant activity in vivo.