[Th2 differentiation features of Mycobacterium tuberculosis heat resistant antigen-activated human γδT cells and the regulation of transcription factor T-bet/GATA-3 on differentiation]

Abstract

Objective: To investigate Th2 differentiation features of Mycobacterium tuberculosis heat resistant antigens (MTB-HAg)-activated human γδT cells and the regulation of transcription factor T-box expression in T cells (T-bet) and GATA-binding protein 3 (GATA-3) on differentiation.

Methods: Peripheral blood mononuclear cells (PBMCs) were stimulated with MTB-HAg to generate MTB-HAg-activated T cells (MTBAT) and expanded in the neutral condition or Th2 polarizing condition. After restimulation for 6 hours with phorbol myristate acetate (PMA, 10 ng/mL), ionomycin (500 ng/mL) and monensin (2.5 μmol/L), intracellular cytokines (IFN-γ, IL-4) of γδT cells and αβT cells among MTBAT were detected by four-color fluorescence mAb staining combined with flow cytometry. The highly purified γδT cells and CD4⁺ T cells were sorted by flow cytometer from MTBAT that were cultured in neutral and Th2 polarizing conditions for 28 days. The expressions of T-bet and GATA-3 mRNA in purified γδT cells and CD4⁺ T cells were determined by reverse transcription PCR (RT-PCR) technique.

Results: γδT cells among MTBAT cultured in the neutral or Th2 polarizing condition predominantly produced IFN-γ, whereas the percentage of IFN-γ⁺ αβT cells significantly decreased in the Th2 polarizing condition as the culture time went by. Compared with the neutral condition, Th0 type (IFN-γ⁺ IL-4⁺) γδT cells significantly increased, and Th2 type (IFN-γ⁻ IL-4⁺) αβT cells also significantly increased in the Th2 polarizing condition. RT-PCR showed that mRNA expression of T-bet was still at a high level in γδT cells that were expanded in the Th2 polarizing condition, but at a low level in Th2 polarized CD4⁺ T cells. Moreover, the mRNA expressions of GATA-3 in both Th2 polarized γδT cells and CD4⁺T cells were up-regulated.

Conclusion: In the Th2 polarizing condition, the majority of γδT cells in MTBAT still remained Th1 profile, whereas the portion of γδT cells differentiated into Th0 type cells. Both transcription factor T-bet and GATA-3 failed to display a fully cross-regulation function in Th2 polarized γδT cells.