General summary

The blood clotting, fibrinolytic, renin–angiotensin, kinin forming systems, and complements are all systems of greater or lesser complexity. Complement with its nine components, with one of the components of human complement, C'1 consisting of three subcomponents, is the most complex; the intrinsic blood clotting mechanism running it a very close second, if not a dead heat. In addition, in each system it is necessary to consider varying number of inhibitors and activators. In no system have all the components of that system been fully characterized, although excellent progress on this score has been made in regard to the blood clotting system and complement. The need for the isolation, purification and thoroughgoing physico-chemical characterization of the components of the kinin forming system is pressing. For it is only by such characterization, and by reconstitution of the system with pure, individual components that the present hypothesis as to the sequence of reactions in this system will be supported or refuted, and the nature and significance of the reported heterogeneity of kallikrein (kininogenase) PF(dil) (PF), and kininogen, be understood. Similarly, it is only through isolation and purification that the nature of the plasminogen activators of plasma and of tissue will be ultimately clarified. Although such isolation and purification will not solve the questions of the in vivo nature and significance of these systems it will aid mightily in their solution. The enzymes in each of the five systems are broadly of the same kind, being mainly proteases, or peptidases. However, with complement recent evidence to be published shortly in the Journal of Immunology indicates, that in addition to the proteolytic activity of C'3, there is also an enzymatic action of either C'8 or C'9 on the phospholipids of the red cell membrane.