The current knowledge of immunological responses to
schistosomiasis is insufficient for the development of
vaccine and
therapies. The role of T follicular helper (Tfh) cells in schistosome
infections is not fully defined. The frequency of circulating Tfh cells and serum
cytokine levels were analyzed in 11 patients with chronic
schistosomiasis and 10 healthy controls (HC), who reside in an endemic area for
Schistosomiasis japonicum. Significantly higher frequencies of circulating CXCR5(+) CD4(+) Tfh cells and higher expression levels of ICOS and PD-1 in CXCR5(+) CD4(+) Tfh cells were observed in patients with chronic
schistosomiasis compared to HC. The levels of
IL-21 in serum and the expression of
IL-21 mRNA were higher in chronic
schistosomiasis patients than in HC. Moreover, the frequency of circulating PD-1(high) CXCR5(+) CD4(+) Tfh cells positively correlated with the levels of
IL-21 in serum from patients with chronic
schistosomiasis. A positive correlation was also found between the frequency of PD-1(high) CXCR5(+) CD4(+) Tfh cells and the levels of soluble egg
antigen (SEA)-specific
antibodies in serum samples from the patient group. Our study is the first regarding Tfh cells in chronic human
schistosomiasis and the finding indicate that PD-1(high) CXCR5(+) CD4(+)Tfh cells might play an important role in the production of specific
antibodies in
schistosomiasis. This study contributes to the understanding of immune response to
schistosomiasis and may provide helpful support in
vaccine development.