A possible effect of the old systemic environment may neglect rejuvenation effect of young Factors (e.g. Young Plasma Injection), stem cell transplantation (bone marrow transplantation into aged irradiated hosts) or constant exchange of blood cells and factors from young partners (Heterochronic Parabiosis). Therefore, transplantation of young lymphoid organs may rejuvenate immune system.
Neonatal lymphoid organs can be transplanted under the kidney capsule and after 3 months the primary response to SRBC can be determined.
Thymus graft from young to old animals has a positive effect on the grafted spleen cellularity and PFC (plaque-forming cell) number in CBA/Ca mice [Physiol J. 1996].