Thymectomy in acute systemic lupus erythematosus and rheumatoid arthritis.

Abstract

Much of the mystery surrounding the function of the thymus gland was dispelled by the demonstration that its removal shortly after birth resulted in an impaired capacity to respond to various antigenic stimuli, including tissue homografts and injections of bacteria and of foreign proteins (Archer and Pierce, 1961 ; Miller, 1961). These observations have now been made in several mam malian species, and it is well established that the thymus plays a vital part in the development of the lymphoid tissues and of normal immune responses: much of the evidence has been reviewed by Miller et al. (1962) and is described in a recent symposium (Good and Gabrielsen, 1964). There is good evidence that the thymus secretes a humoral factor capable of stimulating lymphopoiesis in other lymphoid tissues (Levey et al., 1963 ; Osoba and Miller, 1964), and it is also likely that it produces large numbers of lymphocytes (Nossal and Gorrie, 1964 ; Sainte-Marie and Leblond, 1964), though this has not been established with certainty. Though the thymus undergoes involution in adult life, lymphocytic mitotic activity, while not as prominent as in early life, maintains a high level, and in recent observations Metcalf (1965), Miller (1965), Miller et al. (1965), and Taylor (1965) provide evidence that thymectomy in the adult mouse is followed after an interval of several months by a depression of immune responsiveness. Apart from thymic tumours, the only condition for which thymectomy is commonly performed in man is myasthenia gravis. The changes in the thymus in this condition commonly include the formation of germinal centres, and both this and the demonstration of immunoglobulin (IgG) in the thymus in myasthenia (White and Marshall, 1962) suggest that it may be the site of an abnormal immune response. The detection of auto-antibodies reacting with skeletal muscle in the serum of some patients with myasthenia raises the further possibility that the, abnormal response is of an autoimmune nature. The thymus has not been studied extensively in the various other diseases in which auto-antibodies are commonly present, but thymic abnormalities, including formation of germinal centres, have been described in some cases of Hashimoto's disease, thyrotoxicosis, Addison's disease, systemic lupus erythematosus,