Thymic influence on the T-lymphocyte self MHC repertoire. I. Helper T-lymphocyte precursors.
We measured the frequencies of helper T-cell precursors in spleens of allogeneic thymus-grafted nude mice to determine whether allogeneic thymus engraftment resulted in clonal deletion of helper T-cells reactive to thymic major histocompatibility complex alloantigens, thereby producing tolerance to the thymic alloantigens. C3H thymus-grafted nudes had nearly normal numbers of C3H-reactive helper T-cell precursors, whereas C57BL/6 thymus-grafted nudes had significantly reduced numbers of C57BL/6-reactive helper T-cell precursors. Additional evidence suggested that tolerance was not due to a paucity of helper T-cell precursors: a) there was no correlation between the helper T-cell precursor frequency and the ability to mount cytotoxic responses against the thymic alloantigens, and b) exogenous helper factors did not break cytotoxic T-lymphocyte tolerance to thymic alloantigens. Thus, we conclude that immune tolerance resulting from engraftment of allogeneic thymic tissue is not necessarily due to clonal deletion of specific helper T-cell precursors.
Jenski
L J
LJ
Hematology/Oncology Division, Children's Hospital Research Foundation, Cincinnati, OH 45229.
Belloni
M L
ML
Miller
B A
BA
D000818:Animals; D008285:Major Histocompatibility Complex; D051379:Mice; D008815:Mice, Inbred Strains; D008819:Mice, Nude; D013234:Stem Cells; D013601:T-Lymphocytes / Q000276:immunology*; D006377:T-Lymphocytes, Helper-Inducer; D013950:Thymus Gland / Q000502:physiology*