[Immunology in the aged].

On account of their katabolic status in general, elderly people show increasing involution of every organ and tissue. In addition to the decrease in functional vitality, we find morphologic reduction of highly differentiated cells. This process does also affect the immune system. Many diseases of old age (such as infections, malignomas, auto-immunopathies) seems to be brought about by immunodeficiency due to senescence. These diseases are promoted by the reduced production of antibodies against foreign antigens and by the decreased functions of T-suppressor subpopulations. On the other hand, we observe increasing auto-immunity, a rise of circulating immune complexes, and a higher tolerance towards alloantigenetic tissue. It is not easy to decide whether the pathologic immune status is the result of multimorbidity, or whether diseases of old age develop because of senile immunodeficiency. In this connection, our lacking knowledge regarding immunology in old age becomes obvious; moreover, the problem of answering these questions by means of systematic investigation has not yet been solved.