6533b86ffe1ef96bd12cdf42

RESEARCH PRODUCT

T-cell-derived helper factor allows Lyt 123 thymocytes to differentiate into cytotoxic T lymphocytes.

subject

description

IT is generally accepted that the diversity of T-cell responsiveness is generated in the thymus1. It is also known that except for a few Lyt 1 cells all thymocytes express the Lyt 123 phenotype2,3. Surprisingly, thymocytes are poorly responsive in vitro4, and only the medullary thymocytes, comprising 5–10% of the total thymic cell population, show an in vitro responsiveness comparable with that of peripheral T cells5. Cortical thymocytes, comprising 90–95% of all thymocytes, have previously been considered to be immature and immunologically incompetent4. The result reported here show that thymocytes are able to generate alloantigen-, virus- and hapten-specific cytotoxic T lymphocytes (CTL), provided a T-cell-derived helper factor is added to the cultures. Furthermore, through the use of cell separation techniques we conclude that in the presence of the helper factor the great majority of Lyt 123+ thymocytes have the capacity to differentiate into either alloreactive or H–2-restricted CTL.