Evaluation of the Contribution of Major T Cell Subsets to IFN-γ Production in TB Infection by ELISPOT

Abstract

Interferon gamma remains a key effector molecule that is still widely used as the most informative biomarker for screening human immune responses against tuberculosis, particularly in ELISPOT assays. We investigated the participation of CD4⁺ and CD8⁺ T lymphocytes in the PBMC responses to Mycobacterium tuberculosis (Mtb) specific antigens in 33 TB cases and 49 contacts. Responses to ESAT-6 were higher than CFP-10. There was no significant difference in responses to both Mtb antigens between cases and contacts. PBMCs response to ESAT-6 but not CFP-10 in cases was significantly reduced by depletion of CD4⁺ cells whereas CD8⁺ cell depletion had no impact. In conclusion, ESAT-6 is a more recognized antigen in this population, and CD4⁺ lymphocytes are the main participants in IFN-γ response by ELISPOT. Thus, a decline of CD4⁺ T lymphocytes below a critical level might affect the sensitivity of IFN-γ release assays for detecting Mtb infection.

Keywords:

• T lymphocyte subsets
• Tuberculosis
• IFN-γ
• ELISPOT