Age-correlated changes in the lupus erythematosus antigens Ro, La, Sm and RNP of the thymus gland.

The concentrations of the Sm, RNP, La and Ro antigens of thymus glands from rats were determined depending on the developmental stage of the animals. It was found that lupus antigens strongly decrease after birth. Parallel with this change, the activities of the enzymes DNA polymerase alpha and terminal nucleotidyl transferase in the thymus glands drop during maturation and ageing. These biochemical analyses were supported by immunofluorescence studies using human thymus glands. Moreover, it is documented that a redistribution of Sm and Ro occurs during development. Focusing on Sm, fetal thymus glands contain this antigen predominantly in the cytoplasm, while in immature, mature or old animals Sm is found almost exclusively in the nucleus. From these data we conclude that the amounts of the lupus antigens are additional parameters for the age-correlated function of thymocytes.