PREMATURE ESCAPE OF DOUBLE-POSITIVE THYMOCYTES TO THE PERIPHERY OF YOUNG MICE - POSSIBLE ROLE IN AUTOIMMUNITY

Thymectomy of 3-day-old mice induces organ-specific autoimmune disease . To define a relationship between the development of T cells early in the neonatal period and autoimmunity, we studied the thymus and perip heral lymphoid tissues of 3-day-old mice. Lymph nodes, but not spleens , of 3- to 4-day-old mice contained a significant number of thymus-der ived CD4(+)CD8(+) cells that are phenotypically similar to CD4(+)CD8() thymocytes in their level of expression of CD3 and HSA. it is likely that the prematurely exported cells are the progenitors of autoreacti ve T cells because the lymph nodes from 3- to 4-day-old male, but not female, mice which express a transgenic TCR specific for the H-Y Ag co ntained a large number of CD4(+)CD8(+)Tg(+) as well as CD4(-)CD8(+)Tg( +) T cells. Thus, the neonatal thymus is capable of exporting immature T cells that in the absence of a thymus may differentiate into autoim mune effector cells.