Human platelet chemotaxis: requirement for plasma factor(s) and the role of collagen.
Platelets are actively mobile in plasma in vitro and, in addition, they migrate specifically and directionally toward added intact collagen (chemotaxis). Native human, bovine, and equine collagen, suspended in plasma, induce a chemotactic response in human platelets. However, heat-denatured and dinitrofluorobenzene-treated collagen fail to attract platelets. Platelets migrate directionally and specifically to intact native collagen incubated in plasma over a large distance (6 mm) in a very short time (total 15 min), as observed in a newly designed micromaze apparatus. Platelets obtained from donors deficient in plasma factors XII, IX, and VIII showed normal migration and chemotaxis in normal plasma and in their respective factor-deficient plasmas. Although nondirectional movement (mobility) was normal, platelets from a donor deficient in factor XI did not exhibit chemotaxis toward collagen in either factor XI-deficient plasma or in normal plasma. The results indicate that 1) collagen is a physiological substrate for the chemotactic phenomenon, 2) intact chemical and/or structural integrity of collagen is required for the induction of platelet chemotaxis, 3) at least one plasma constituent, factor XI, plays an essential role in the chemotactic phenomenon, and 4) contact between collagen and a plasma factor is essential for normal chemotaxis.