The effect of measles on the thymus and other lymphoid tissues.

The histological changes in the thymus and other lymphoid tissues in cases of severe measles resulting in death during the acute phase or at sometime afterwards (from a presumably unrelated cause) have been surveyed and compared with cases of similar age and duration of illnesses other than measles which were admitted to the same infectious diseases hospital. Severe changes of aggregation and formation of large syncytia of thymocytes which progressed to cytoplasmic and nuclear destruction were observed early in the disease (at 4 days). These `giant-cells' failed to show either nuclear or cytoplasmic inclusion bodies. Such cases when seen at a later stage had total loss of thymic cortex. After measles the cortex of the thymus can be absent for at least 2 months. Thus no cortex was discernible in cases of post-measles death at 28 and 64 days; recovery of cortex was seen at 91 and 122 days. Other cases of severe systemic disease entering the same hospital also showed loss of thymic cortex from 6 days of illness. Thus, although measles-determined aggregative destruction of thymocytes can cause rapid loss of cortex, the final histological picture of the latter need not necessarily have been preceded by the same type of measles-dependent thymocyte destruction. Although thymocyte aggregation and secondary depletion were the most obvious histological result, a careful quantitation of the medulla and of HassalFs corpuscles showed a small decrease in both tissues in the acute phase. Cases recovering from measles showed a small decrease in the number of Hassall's corpuscles. Measles-specific changes were not found in lymphoid tissues other than the thymus of these cases.