Histocompatibility typing by cellular radioimmunoassay
B M Longenecker1, B Singh, M Gallatin
1Department of Immunology, The University of Alberta, 845E Medical Sciences Building, T6G 2H7, Edmonton, Alberta, Canada.
Insights
A new quantitative cellular radioimmunoassay (CRIA) offers highly sensitive histocompatibility typing. This method accurately detects minor cell populations and erythrocyte chimerism in chickens.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Histocompatibility typing is crucial for transplantation and genetic studies.
- Conventional methods like hemagglutination assays lack sensitivity and objectivity.
- There is a need for more sensitive and precise assays to detect minor cell populations and chimerism.
Purpose of the Study:
- To describe a novel quantitative cellular radioimmunoassay (CRIA) for histocompatibility typing.
- To evaluate the sensitivity and consistency of the CRIA assay.
- To demonstrate the utility of CRIA in detecting erythrocyte chimerism and tumor-specific antigens.
Main Methods:
- Chicken red blood cells (RBC) were incubated with specific anti-MHC (B) alloantisera in microtiter plates.
- Bound alloantibody was measured indirectly using (125)I-labeled rabbit anti-chicken IgG.
- CRIA was applied to artificial cell mixtures, induced erythrocyte chimerism in chickens, and a T-cell lymphoma model.
Main Results:
- The CRIA assay demonstrated high sensitivity, detecting as little as 1% of relevant cells in mixtures.
- Erythrocyte chimerism in chickens was precisely quantitated, with percentages ranging from 13-40% in chimeric animals.
- The assay successfully detected tumor-specific antigens and revealed unexpected binding patterns of anti-B(15) alloantibody.
Conclusions:
- CRIA is a highly sensitive, objective, and consistent method for histocompatibility typing.
- The assay is effective for quantitating erythrocyte chimerism and detecting minor cell subpopulations.
- CRIA has potential applications in tumor immunology and understanding alloantigen expression.
Abstract:
A quantitative cellular radioimmunoassay (CRIA) for histocompatibility typing is described. Chicken red blood cells (RBC) were incubated in microtiter plates with specific anti-MHC (B) alloantisera and the alloantibody bound measured indirectly by a second binding step with(125)I-labeled rabbit anti-chicken IgG. The assay is objective, highly consistent, and three to four orders of magnitude more sensitive than conventional hemagglutination assays. The new CRIA was used to detect minor subpopulations of cells in artificial cell mixtures; as few as 1% of relevant cells were easily detected. Erythrocyte chimerism was induced following the injection of B(2)/B(2) chicken embryos with B(15)/B(21) embryonic stem cells. Five weeks after hatching, erythrocyte chimerism was precisely quantitated by comparing the reaction of RBC from the putative chimeras with artificial cell mixtures using specific anti-B(15)/B(21) alloantisera. The percent varied from 13-40% in 13 chimeric animals. The new CRIA was also used for the sensitive detection of tumor-specific antigens on a T-cell lymphoma. An unexpected finding was that anti-B(15) alloantibody bound almost as well to B(15)/B(21) heterozygous RBC as to B(15)/B(15) homozygous cells, suggesting that either the concentration or the steric arrangement of B(15) alloantigen at the erythrocyte surface may not conform to conventional expectations.
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