Platelet factor 4 is chemotactic for neutrophils and monocytes.

Abstract

Platelet factor 4 is a chemotactic protein for human polymorphonuclear leukocytes and monocytes at concentrations found in human serum and reached locally in injured tissue. The maximum chemotactic response to platelet factor 4 nearly equals that achieved with saturating concentrations of the chemotactic activity derived from the 5th component of human complement, C5. Cells desensitized to C5 chemotactic activity retain chemotactic responsiveness to platelet factor 4. Serum contains inhibitory capacity against the chemotactic activity associated with activity with platelet factor 4. The local release of platelet factor 4 may be an important stimulus attracting inflammatory cells to sites of blood vessel injury.