Partial Immunological Restoration of Neonatally Thymectomized Rats with Thymus-containing Diffusion Chambers

Abstract

SEVERAL investigators have demonstrated the important part of the thymus in the development of immunological competence^1–3. A point of considerable significance is whether this thymic function is mediated by a cellular or a humoral mechanism. There is both direct and indirect evidence of a humoral factor in thymic activity in the mouse. Thus, genetic studies have established that the cellular constitution of thymus tissue grafted to mice thymectomized at birth is of host rather than donor origin^4,5, and other work has established that partial immunological restoration of such thymectomized mice can be achieved by thymus-containing diffusion chambers which do not permit the passage of whole cells^6,7. However, since the restorative effect of such chambers is incomplete, and since thymic extracts have not produced appreciable restoration, it remains unsettled whether a cellular mechanism is involved in addition to the humoral one and investigation in a second species appears to be warranted. The present note reports our investigations over the past 18 months of immunological restoration of neonatally thymectomized rats with thymus-containing diffusion chambers. The results are in general agreement with the mouse experiments, and show that partial immunological restoration is achieved but the restored animals are not immunologically normal.