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p30-Anti-p30 immune complexes: intravascular clearance and extravascular sequestration in rats bearing Moloney
Abstract:
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.
Insights
Antibody-antigen complexes cleared rapidly in tumor-bearing rats, primarily sequestered in the spleen. This rapid clearance of viral core polypeptide (p30) complexes suggests removal by the reticulo-endothelial system.
Area of Science:
- Immunology
- Oncology
- Virology
Background:
- Viral core polypeptides, such as p30, can elicit immune responses.
- Antibody-antigen complex formation is a key immunological process.
- Tumor microenvironments can influence immune complex pharmacokinetics.
Purpose of the Study:
- To investigate the in vivo fate of preformed 125I-labeled p30-antibody complexes.
- To determine if tumor burden affects the clearance and tissue distribution of these complexes.
- To elucidate the mechanisms underlying complex sequestration in tumor-bearing rats.
Main Methods:
- Intracardiac injection of 125I-labeled p30-antibody complexes into BN rats.
- Comparison of complex clearance and tissue distribution in rats with Moloney sarcomas (MST), unrelated tumors, and controls.
- Quantification of radioactivity in serum and various tissues over time.
- Assessment of complex binding to peripheral blood and spleen cells.
Main Results:
- Complexes were cleared more rapidly from the circulation of MST-bearing rats compared to controls.
- Rapid elimination of complexes was observed within 30 hours post-injection.
- The spleen showed significantly higher sequestration of complexes in MST-bearing rats.
- No significant concentration of complexes was found in tumor tissue or binding to peripheral blood cells.
Conclusions:
- Augmented clearance and splenic sequestration of p30-antibody complexes in tumor-bearing rats.
- These phenomena are likely due to the formation of large, insoluble complexes.
- Rapid removal by the reticulo-endothelial system is the probable mechanism for complex elimination.