Role of T lymphocytes in adjuvant arthritis. I. Evidence for the regulatory function of thymus-derived cells in the induction of the disease.

Rats of Wistar King Aptekman (WKA) were thymectomized at 4 weeks of age and injected with Mycobacterium tuberculosis wax D 6 weeks after the operation to induce adjuvant arthritis. The development of this disease was strikingly enhanced by this treatment. Further experiments showed that a 4- to 6-week interval between thymectomy and wax D injection was necessary to show the enhancing effect. Such enhancement by thymectomy was also shown in rats of another strain, Sprague-Dawley (SD). The enhancing effect of thymectomy was abolished when thymocytes of normal syngeneic rats were transferred to thymectomized rats 7 days before the wax D inoculation. Furthermore, severe arthritis was also produced in WKA rats that were pretreated with low dose (200 R) whole body irradiation, but not in those treated with higher doses (400 to 700 R). These results seem to indicate that the enhancing effect is brought about by selective depletion of a certain population of T lymphocytes. The population depleted may be thymus dependent, short-lived and radiosensitive, the properties of which agree whith those known for suppressor T lymphocytes. Thus, it appears that thymus-derived cells could normally exert a regulatory effect on the development of adjuvant arthritis which might render these rat strains relatively less susceptible to this disease.