cTfh17.1 cells were the major subtype for IL-21 production in MS
patients
As shown in Fig. 3d and e, the level of IL-21 secreting cTfh cells was
significantly higher in MS patients. We then examined the secretion of
IL-21 by different subsets of cTfh cells and compared between HC and MS
patients. Although all the four subtypes of cTfh cells produce IL-21,
cTfh17.1 cells were associated with the greatest production of IL-21 in
both HC and MS (Fig. 4a,b). Interestingly, IL-21 secreting cTfh17.1
cells was significantly higher in MS patients (52.52±4.86% vs.
24.81±5.34%, p=0.002) than that in HC (Fig. 4a,b). However, other
subsets of IL-21 secreting cTfh cells did not differ significantly
between HC and MS. We also analyzed and compared IL-17 secreting cTfh17
cells in HC and MS patients, followed by a comparative analysis of IL-17
production by cTfh17 vs. non-follicular Th17 cells. We found no
noticeable difference in IL-17 secreting cTfh17 cells between HC and MS
(Fig. 4c and S3a). Moreover, IL-17 secreting cTfh17 versus
non-follicular Th17 cells did not show any differences between HC and MS
(Fig. 4d and S3a,b,e,f). However, a significant increase of
CXCR3+CCR6+ cTfh17.1 cells in MS
patients led us to investigate them further based on the cytokine types,
especially IFN-γ and IL-17. Along with IL-21, cTfh17.1 cells also
produced IFN-γ and IL-17 with different frequencies (Fig. S3c,d and Fig.
4e,f), although no significant difference was observed between HC and MS
regarding IFN-γ and IL-17 secreting cTfh17.1 cells. Importantly, IL-21
was the major cytokine secreted by the cTfh17.1 subtype over others
suggesting that cTh17.1 cells are the major secretor of IL-21 in MS
patients.