Course of lymphocytic choriomeningitis virus infection in young and aged mice.

The course and histological picture of intracerebral LCM virus infection was found to differ in mice with their thymus displaying an age-dependent involution and in young adult animals. Signs of lymphocytic choriomeningitis were absent in 75 per cent of the aged animals. The change of the characteristic clinical and histological picture referred to the decreased cellular immune response of aged animals, ascribed to the age-dependent involution of the thymus.