Follicular Helper T Cells in Pulmonary Tuberculosis: A Retrospective Study

Follicular helper T lymphocyte (Tfh) promotes antibody production by B lymphocytes in various diseases, including Pulmonary Tuberculosis (PTB).

To explore the potential role of Tfh cells and assess the expression level of PD-1, and IL-21 in PTB.

54 newly diagnosed smear-positive PTB, 27 people with latent tuberculosis (LTB) and 27 healthy controls (HC) were enrolled. The PTB group was further divided based on the range of lung field involved (focus number>=3, PTB-X3; <3, PTB-X2). After 6-month therapy, sputum smear (positive, PTB-SP; negative, PTB-SN) or imaging examinations (lesion reduction significant, PTB-os; insignificant, PTB-s) were used to evaluate the conditions of PTB patients. Blood samples were collected from PTB group at month six. CD4+CXCR5+Tfh, and its subsets, CD4+CXCR5+PD-1+Tfh and CD4+CXCR5+ICOS+Tfh in peripheral blood mononuclear cells (PBMCs) were detected. Serum IL-21 concentrations were measured.

The frequencies of CD4+CXCR5+Tfh, CD4+CXCR5+ICOS+Tfh and CD4+CXCR5+PD-1+Tfh were higher in PTB group than in HC. IL-21, IL-4 and IFNγ concentrations were significantly higher in PTB group than in HC. The proportion of CD4+CXCR5+Tfh in PTB-X2 was lower than in PTB-X3 group. CD4+CXCR5+PD-1+Tfh proportion in PTB-X2 was lower than that in the PTB-X3. After treatment, CD4+CXCR5+Tfh proportion was significantly lower in the PTB-SN group. CD4+CXCR5+Tfh was lower in the PTB-os group than in the PTB-s group. However, the CD4+CXCR5+PD-1+Tfh and cytokine concentrations of IL-21 were not different.

CD4+CXCR5+Tfh level might predict the sputum results, and lesion decrease rate while CD4+CXCR5+PD-1+Tfh subset and IL-21 were not associated with sputum results or lesion decrease after treatment.