FAS and tuberculosis: In addition, the percentage of Fas/FasL-expressing Vγ9Vδ2 T cells in the peripheral blood of IGRA-negative TB patients was significantly higher than in IGRA -positive TB patients, suggesting that the decrease in the number of Vγ9Vδ2 T cell may be related to the increase in Fas/FasL-mediated induced cell apoptosis.