CD40 Ligand Expression Is Developmentally Regulated in Human Thymocytes

Ramsay Fuleihan, Deborah Ahern, Raif S. Geha

Research output: Contribution to journalArticle

14 Scopus citations


Thymic selection involves the interaction between developing thymocytes and the thymic microenvironment. CD40 is expressed on thymic epithelial cells and on bone marrow-derived antigen-presenting cells in the thymus. We have investigated the capacity of human thymocytes to express CD40 ligand. CD40 ligand was not detectable on resting immature double-positive (CD4+/CD8+) or resting mature single-positive (CD4+/CD8- or CD4-/CD8+) thymocytes. Immature thymocytes failed to express CD40 ligand on their surface after stimulation with PMA and ionomycin, whereas stimulated CD4+/CD8- mature thymocytes expressed CD40 ligand. Northern blot analysis revealed that CD40 ligand mRNA was detectable in activated mature single-positive thymocytes. CD40 ligand expression by mature thymocytes was associated with the capacity to drive immunoglobulin isotype switching in purified B cells. These results demonstrate that the ability to express CD40 ligand is acquired late in thymocyte development and that mature thymocytes are capable of providing B cells with the activation signals necessary for immunoglobulin isotype switching.

Original languageEnglish (US)
Pages (from-to)52-58
Number of pages7
JournalClinical Immunology and Immunopathology
Issue number1
Publication statusPublished - Jul 1995


ASJC Scopus subject areas

  • Immunology and Allergy
  • Pathology and Forensic Medicine
  • Immunology

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