Presence of a Non-polymorphic Polypeptide Chain in Ia Immunoprecipitates

• Published in: The Journal of immunology (1950) Vol. 121; no. 4; p. 1609
• Main Authors: Jones, Patricia P, Murphy, Donal B, McDevitt, Hugh O
• Format: Journal Article
• Language: English
• Published: Am Assoc Immnol 01.10.1978
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.121.4.1609.a

Abstract All immunoprecipitates prepared from NP-40 extracts of 35S-methionine-labeled mouse lymphocytes using anti-Ia alloantisera contain a common polypeptide chain, MW 31,000 daltons. The electrophoretic mobility of this molecule in two-dimensional polyacrylamide gel electrophoresis is the same for Ia antigens coded for by loci in the I-A and I-E subregions and for molecules obtained from mice of different H-2 haplotypes and genetic backgrounds. Immunoprecipitates obtained with anti-H-2K, anti-H-2D, and anti-immunoglobulin antisera do not contain this polypeptide chain. This molecule therefore appears to be a nonpolymorphic protein unique to Ia immunoprecipitates. Because it is nonpolymorphic, this chain probably is not recognized by alloantisera and hence may be precipitated only because it is complexed to polymorphic Ia proteins. Thus the occurrence of this invariant chain with Ia antigens appears to be analogous to that of β2 microglobulin, a nonpolymorphic polypeptide chain coprecipitated with H-2K and H-2D antigens.