Lack of effect of thymus and spleen on the incubation period of Creutzfeldt-Jakob disease in mice.

Genetically athymic and asplenic (Lasat), athymic (Nude), asplenic (Dh) or normal littermate (Hetero) mice with a BALB/c genetic background were injected either intracerebrally or intraperitoneally with a 1% or 10% homogenate of mouse brains infected with the Fukuoka 1 strain of the Creutzfeldt-Jakob disease (CJD) agent. As there were no significant differences in incubation periods among the five groups (Lasat, Nude, Dh, Hetero and BALB/c) inoculated with the same dilution, via the same route, it was concluded that cell-mediated immunity dependent on the thymus plays no significant role in host defence against the CJD agent, and the spleen, a critical site of agent replication, is apparently not an obligatory source from which infection spreads to the central nervous system.