p30-Anti-p30 immune complexes: intravascular clearance and extravascular sequestration in rats bearing Moloney sarcoma.

Complexes of 125I p30, a viral core polypeptide, and rat anti-p30 antibody, preformed in vitro, were injected into the heart of BN rats bearing Moloney sarcomas (MST) and of BN rats bearing an unrelated tumor or unexposed to tumor. Complexes were cleared from the circulation of MST-bearing rats more rapidly than from sera of controls and were almost completely eliminated after 30 hr. There was no relationship between rate of disappearance and size of tumor or levels of circulating complexes. Disappearance rates in rats with progressing and regressing tumors were similar. Uncomplexed labeled p30 was cleared from the circulation of tumor-bearing and control rats with kinetics similar to those of labeled complexes. Complexes were localized in the spleen of tumor-bearing and control rats, but much more in spleens of MST-bearing rats. No other tissues, including tumor, concentrated complexes, nor was there binding to peripheral blood and spleen cells. The data suggest that augmented clearance and sequestration were due to the formation of large insoluble complexes that were rapidly removed by the reticulo-endothelial system.