RETENTION OF INTACT HSA FOR PROLONGED PERIODS IN THE POPLITEAL LYMPH-NODES OF SPECIFICALLY IMMUNIZED MICE

The rate of clearance of radiolabel was studied from the popliteal lymph nodes of either nonimmune or specifically immunized mice following footpad injection of 125I-labeled HSA. The 125I was more rapidly and more completely eliminated from the nodes of nonimmune mice than from the nodes of specifically immunized animals. Autoradiographs showed that, whereas the radiolabel was strictly confined for long periods to the follicles of the nodes of immune mice, no such localizaton was present in nonimmune animals. Solubilization of the whole nodes with 5 M guanidine-HCl released the labeled material which could then be specifically precipitated with anti-HSA but not with anti-EA. Such specifically precipitable material could be extracted from the draining popliteal lymph nodes of the immune mice even 12 weeks after challenge. Analysis of the solubilized radioiodinated lymph node extract on Sephacryl S-200 gels showed that the majority of the material was indistinguishable from the 125I-labeled HSA used for challenge. The radiolabel therefore remains attached to intact HSA for long periods in vivo in immune animals which have a highly developed mechanism for clearance of simple protein antigens. These data suggest that intact antigenic determinants can persist for prolonged periods and may play a role in the long-term maintenance and regulation of immune responses. © 1979.