Brown adipose tissue and immunity. Effect of neonatal adipectomy on humoral and cellular immune reactions in the rat.

This work concerns the involvement of brown adipose tissue in the immune system ofthe rat. Wistar rats were thymectomized, adipectomized (surgical extirpation of the interscapular brown adipose tissue), thymectomized and adipectomized, and sham-operatedat birth, only 8-week-old females being employed in the experiment. The production of antibody to bovine werum albumin (BSA) and sheep red blood cells (SRBC), delayed skin reactions to BSA, rejection of thyroid allograft implanted under the kidney capsule, and development of experimental allergic encephalomyelitis were investigated. Neonatal adipectomy did not affect the production of anti-BSA and anti-SRBC antibodies. On the other hand, delayed skin reactions to BSA, rejection of thyroid allograft, and incidence and severity of allergic encephalomyelitis were much more pronounced in adipectomized animals. It has been postulated that the immune function of brown adipose tissue is an expression of the secretory activity of the tissue. Since the immunosuppressive effect of neonatal thymectomy on demyelinating disease was neutralized by neonatal adipectomy, and vice versa, and since thymectomy rendered ineffective the immunopotentiating influence of adipectomy on this disease, as demonstrated in thymo-adipectomized rats, it was concluded that the brown adipose tissue is a naturalantagonist of the thymus in cell-mediated immunity. This paper also describes the extra thymuses which were situated in the vicinity of the thyroid and parathyroid lobes of23.2 per cent of rats.