Mary Ruth Smith

The role of c3 as an opsonin in the early stages of infection.

Summary In order to investigate the role of C3 in host defense in vivo, normal AKR/J mice, genetically deficient in C5, were depleted of serum C3 by the injection of purified cobra venom factor (CoVF). Concurrent with their C3 depletion, their serum opsonizing activity decreased to a level less than 20% of normal. When these mice were challenged with an intraperitoneal injection of pneumococci 2 hr after the CoVF treatment, the LD50 was from 30 to 80 times lower than the LD50 in saline-treated control animals. When the CoVF was given only 6 hr after the pneumococcal challenge, the LD50 was the same as in the control mice. If the pneumococci were first preopsonized in vitro and then injected into CoVF-treated animals, the LD50 was the same as that in control animals. These experiments demonstrate that C3 plays a significant role in vivo in the hosts defense against infection and that a major part of that role is through its action as an opsonin. Furthermore, these experiments demonstrate that the role of C3 is most significant during the early stages of bacterial invasion. The authors are grateful to Andrea Swift for her expert technical assistance.

Internationales Komplement Symposion 14. und 15. Juli 1969 in Mainz

A technique has been developed allowing the detection of C lq activity in an agarose gel containing EA and an RClq. This latter reagent consists of fresh human serum, which has been depleted of Clq by means of a specific rabbit anti-Clq ant ibody in the presence of EDTA. In a Petri-dish containing such a gel, lysis of EA can be shown around wells filled with purified Clq. The system can be used to detect Clq activity in a cell suspension. Washed blood leucocytes from human origin are separated by means of eentrifugation on an albumin gradient. A population of mononucleated cells can be isolated which releases Clq. This activity is revealed as hemolytic plaques occurring around some of the cells after incubation at 37~ the reation can be inhibited by specific anti-Clq. The type of the cells involved in the release of this complement factor is currently being investigated.

WHOLE BLOOD MEASUREMENT OF PROTHROMBIN TIME AND ACTIVATED PARTIAL THROMBOPLASTIN TIME IN A PEDIATRIC POPULATION. 927

WHOLE BLOOD MEASUREMENT OF PROTHROMBIN TIME AND ACTIVATED PARTIAL THROMBOPLASTIN TIME IN A PEDIATRIC POPULATION. 927

THE BIOLOGIC SIGNIFICANCE OF THE THIRD COMPONENT OF COMPLEMENT |[lpar]|C3|[rpar]| IN NONIMMUNE HOST DEFENSES

Studies performed in vitro have demonstrated that C3 acts as an opsonin when activated to C3b and fixed to bacteria. In order to investigate the significance of C3 as an opsonin in vivo the following experiments were performed in normal, nonimmune mice.Mice were totally depleted of serum C3, as measured in a hemolytic assay, by the injection of cobra venom factor(CoVF). Concurrent with the C3 depletion their serum opsonizing activity decreased to a level less than 20% of normal. When mice were challenged with an intraperitoneal injection of pneumococci(Pn) immediately after the CoVF treatment, the LD50 was 1.8 × 106 as compared to 6.8 × 107 in saline treated control animals (P<0.05). When the CoVF was given only 6 hours after the Pn challenge the LD50 was the same as in the control mice. If Pn were preopsonized in vitro with nonimmune mouse serum and then injected into CoVF treated animals, the LD50 was the same as that in control animals.These studies demonstrate that there is a biologically significant in vivo role for C3 as an opsonin in the nonimmune hosts defense against bacterial infection and that that role is most significant in the early stages of bacterial invasion.