Model approach to immunological rejuvenation of the aged.

Reconstitution of a damaged or exhausted immune system by injection of genetically compatible immunocompetent cells (immunologic rejuvenation) is a promising approach for restoration of immune activity. By using this model, spleen cells from young-adult mice, previously immunized with Salmonella typhimurium, were transferred to either young-adult or old, syngeneic recipients before or after storage at -196 C. The susceptibility of recipient mice was then determined by challenging them at increasing time intervals after reconstitution with lethal doses of the virulent organisms. The findings, although preliminary in nature, demonstrate that (i) immunological rejuvenation of mice is possible with immunocompetent cells from specifically immunized donors; (ii) prolonged "takes" of these cells can occur even in nonirradiated recipient mice, and (iii) storage at -196 C does not impair their protective capacity.