SMALL CD4(+)8(+)TCR(LOW) THYMOCYTES CONTAIN PRECURSORS OF MATURE T-CELLS

To evaluate directly the developmental potential of cortical CD4(+)8(+) thymocytes, highly purified populations of small, nondividing CD4(+)8(+)TCR(low) and large, dividing CD4(+)8(+)TCR(high) thymocytes from H-2(d) mice expressing a transgenic T cell receptor restricted by H-2D(b) (major histocompatibility complex class I) molecules were transferred into the thymus of normal, nonirradiated H-2(b) recipient mice. The results show that both populations generate CD4(-)8(+) thymocytes under these conditions, thus providing conclusive evidence that small cortical thymocytes do not represent a 'dead end' but an important intermediate stage in T cell development.