Host defense in cryptococcosis. III. Protection of nude mice by thymus transplantation.

Congenitally athymic (nude) BALB/c mice, which are homozygous for the nu gene, are extremely susceptible to challenge with Cryptococcus neoformans. Groups of nude mice received transplants of thymus tissue obtained from either heterozygous (nu/+) mice or normal BALB/c mice not carrying the nu gene. Survival and delayed-type hypersensitivity were measured after challenge with cryptococci. Mice that received thymus tissue from a heterozygous (nu/+) or normal BALB/c mouse donor had markedly prolonged survival after challenge. In addition, mice that received thymus tissue from normal BALB/c mice developed delayed-type hypersensitivity to cryptococcal antigens following challenge. These studies indicate that transplantation of thymus tissue effectively increases host immune resistance against C. neoformans.