Enhanced vascular permeability and haemorrhage-inducing activity of rabbit C5a(des arg): probable role of polymorphonuclear leucocyte lysosomes

We previously reported that the injection into rabbit skin of rabbit zymosan-activated plasma (ZAP) induces marked polymorphonuclear leucocyte (PMN) infiltration, a transient increase in vascular permeability (1 hr) and prolonged red blood cell extravasation lasting at least 10 hr. Here we describe the fractionation of ZAP to identify the factor(s) responsible for these effects. On CM Sephadex G-25 chromatography, the majority of the leucocyte-attracting, permeability-enhancing and haemorrhage-inducing activities eluted in the high-salt fractions (0.6M ammonium formate, 1 M NaCl pH 5.0), suggesting that this is a very basic molecule(s). Furthermore, the three activities eluted in the same fraction on Sephadex G-100, with an apparent molecular weight of 14,000 - 17,000 daltons. These observations, and the previously described requirement for C5 in the plasma, suggest that C5a(des arg) is the active factor. Experiments performed in neutropenic rabbits indicated that PMN are required for both the increase in permeability and red cell extravasation. Ultrastructural studies showed extensive degenerative changes in the infiltrating PMNs evident even in 1-2 hr lesions. These ranged from 'watery' cytoplasm, loss of glycogen and cell membrane to segregation and extensive extracellular release of lysosomes. It is postulated that C5a(des arg)-induced chemotaxis and metabolic perturbations contribute to this rapid degeneration of the PMNs, and that the release of lysosomes from these cells results in progressive vascular injury.