The ligand for positive selection of T lymphocytes in the thymus

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T cells are spared from programed cell death in the thymus after an appropriate interaction between the T-cell receptor and a self peptide/MHC complex; this step is referred to as positive selection. Recent work has focused on precise identification of the positively selecting ligand, and the cell that presents it. First, it was shown that bone marrow derived cells or fibroblasts can substitute for epithelial cells in providing the ligand for positive selection. Second, in a T-cell receptor transgenic system, variants of the antigenic peptides were found to induce positive selection. Peptides that served as antagonists or weak agonists for the T-cell receptor efficiently selected immature thymocytes for survival. It appears that the peptide ligands for positive selection of T cells are self peptides, which serve as mimics or look alikes for the universe of pathogen peptides. The challenge remains to identify a naturally occurring thymic self peptide that can cause positive selection and determine the range of reactivities to foreign peptides which it can select.

Original languageEnglish (US)
Pages (from-to)273-278
Number of pages6
JournalCurrent Opinion in Immunology
Issue number2
StatePublished - Apr 1994

Bibliographical note

Funding Information:
MJ Ikvan is supported by the Howard Hughes Medical Institute and grants from the National Institute of Allergy and Infectious Diseases. SC Jameson is a special fellow of the Leukemia Society.


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