Characterization of antigen-specific receptors from pig lymphocytes.
Antigen-specific receptors were isolated from the surface of spleen and lymph node cells of ARS-BGG-stimulated miniature pigs using an immunoadsorption technique. The yields of the receptors can be increased by 20-hr cultivation of the cells protein-free medium prior to the isolation procedure. In this case antigen-specific molecules can be isolated not only from the surface of the cells but also from the culture medium. 125I-labelled isolated receptors were separated by SDS-PAGE into six fractions. The first corresponded to aggregated molecules and IgG, the mol. wts of the other fractions were 56,000, 35,000, 26,000 and 10,000. It has been shown that they all were able to bind antigen but only the first two reacted with anti-Ig antibodies and Staphylococcus aureus protein A-Sepharose 4B. Gel filtration of the same sample of 125I receptors on Sephacryl S-200 revealed the presence of four peaks. Three of them were able to bind antigen as detected by radioimmunoassay. Fractions of all three peaks reacted also with anti-Id and anti-R (anti-Ig- receptors) antisera, but only fractions of the first two peaks reacted with anti-Ig antisera. The finding that Ig- receptors and more heterogeneous than Ig+ receptors is discussed. No reaction of isolated 125I receptors with anti-SLA and anti-SLB antisera used was detected in the solid-phase radioimmunoassay.