Immunsuppression durch C-Ausschaltung

An improved method is described for extraction from rat myocardium of an enzyme that cleaves the third component of complement (C3) into leukotactic fragments. Direct cleavage of C3 has been shown by the use of a radiolabeled preparation of human C3. The enzyme elutes slightly beyond (retarded to) an albumin marker in gel filtration. After surgical ligation of a coronary artery, leukotactic activity can be extracted from infarcted rat myocardium. Described in terms of its time of appearance in infarcted tissue, the leukotactic activity has been identified as cleavage products of rat C3. The C3 fragments are of low molecular weight and heterogenous in size. Rats, if treated with the C3 inactivator (isolated from cobra venom) so as to ablate serum C3, fail to develop leukotactic activity in the infarcted myocardium. In turn, few if any of the usual intense accumulations of neutrophils in response to infected myocardium are seen during the first 48 hr after coronary artery ligation. These studies suggest a nonimmunologic role for C3 in the mediation of the acute inflammatory response in nonspecific tissue injury.

In acute nephrotoxic nephritis, polymorphonuclear leukocytes (polymorphs) accumulated in large numbers in the glomeruli in the first 12 hours. The endothelial cells were dislodged by the polymorphs which then came to lie immediately adjacent to the glomerular basement membranes. Ultrastructural changes in neither polymorphs nor basement membranes were observed. Depletion of polymorphs in both rats and rabbits prevented the development of proteinuria. This occurred when doses of nephrotoxic globulin were employed that produced proteinurias of as much as 1800 mg/kg/24 hours in intact rabbits, or enough to yield near maximal immediate proteinuria in intact rats. In addition, measurable glomerular damage was frequently averted until the onset of the secondary stage of NTN. Controls indicated that the polymorph depleted animals exhibited minimal non-specific changes in the blood, that the ability of their vascular beds to react to stimuli was not affected, and that deposition of nephrotoxic antibody and C' in the glomeruli was not inhibited. Elimination of polymorphs from the circulation was only partially effective in preventing glomerular damage when large doses of nephrotoxic globulin were used. This indicated that under these circumstances, a polymorph independent glomerular injury may also take place in first stage nephrotoxic nephritis. An indirect role of C', i.e., the accumulation of polymorphs, in bringing about glomerular injury in first stage nephrotoxic nephritis was apparent. When rabbit nephrotoxic globulin was injected into rats depleted of C', or when duck nephrotoxic globulin that fixed C' poorly was injected into normal rats, C' failed to bind with the antibody along glomerular basement membranes and polymorphs did not accumulate.

Rats and guinea pigs were depleted of complement (C') by treatment with heat aggregated human γ-globulin (agg HGG), zymosan, anti-β1C globulin, and carrageenan. Although antigen and antibody were bound to vascular structures, Arthus reactions were inhibited. This inhibition was characterized by the lack of C' binding to walls of vessels, the lack of polymorphonuclear (PMN's) cellular infiltrates, and the lack of significant vascular damage. When the same animals were followed for several hours thereafter, levels of serum C' began to rise, C' was bound in tissues, PMN infiltrates appeared, and immunologic vasculitis developed. Blood counts, chemotaxis of PMN's induced by lysates of PMN granules, together with studies on motility and phagocytosis by PMN's obtained from C' depleted rats, failed to establish any abnormality in these cells which would account for inhibition of Arthus reactions. The specificity of C' depletion in terms of effects in the first four reacting components of guinea pig C' was studied. Treatment with agg HGG led to loss of activity in all components, whereas zymosan and anti-β1C globulin predominately affected the third component (C'3c). Carrageenan mainly affected the first two reacting components of C'. Thus, the availability of the 3c component, or a subsequently reacting component, correlated with the attraction of PMN's to immune reactants in vivo. Various antibodies with different C' fixing capacities in vitro were tested for their ability to induce immunologic vasculitis in normal animals. In rats, only those antibodies which fixed C' in vitro possessed biological activity, whereas in guinea pigs, all antibodies tested, regardless of C' fixation in vitro, induced Arthus reactions. For a given antibody in rats the vasculitis-inducing property was reflected in its ability to bind C' in vascular structures. Rats depleted of circulating PMN's by specific antibody were tested for Arthus activity. Although concentrations of immune reactants and C' were readily detected in vascular structures, no PMN infiltration occurred and significant vascular damage was averted.