Imbalance of Circulating Follicular Regulatory and Follicular Helper T Cell Subpopulations Is Associated with Disease Progression and Serum CYFRA 21-1 Levels in Patients with Non-small Cell Lung Cancer

Objective This study aimed to investigate the changes of follicular helper T (TFH) and follicular regulatory T (TFR) cell subpopulations in patients with non-small cell lung cancer (NSCLC) and their significance. Methods Peripheral blood was collected from 58 NSCLC patients at different stages and 38 healthy controls. Flow cytometry was used to detect TFH cell subpopulation based on programmed death 1 (PD-1) and inducible co-stimulator (ICOS), and TFR cell subpopulation based on cluster determinant 45RA (CD45RA) and forkhead box protein P3 (FoxP3). The levels of interleukin-10 (IL-10), interleukin-17a (IL-17a), interleukin-21 (IL-21), and transforming growth factor-β (TGF-β) in the plasma were measured, and changes in circulating B cell subsets and plasma IgG levels were also analyzed. The correlation between serum cytokeratin fragment antigen 21-1 (CYFRA 21-1) levels and TFH, TFR, or B cell subpopulations was further explored. Results The TFR/TFH ratio increased significantly in NSCLC patients. The CD45RA + FoxP3 int TFR subsets were increased, with their proportions increasing in stages II to III and decreasing in stage IV. PD-1 + ICOS + TFH cells showed a downward trend with increasing stages. Plasma IL-21 and TGF-β concentrations were increased in NSCLC patients compared with healthy controls. Plasmablasts, plasma IgG levels, and CD45RA + FoxP3 int TFR cells showed similar trends. TFH numbers and plasmablasts were positively correlated with CYFRA 21-1 in stages I–III and negatively correlated with CYFRA 21-1 in stage IV. Conclusion Circulating TFH and TFR cell subpopulations and plasmablasts dynamically change in different stages of NSCLC, which is associated with serum CYFRA 21-1 levels and reflects disease progression.