Treatment effects on IL-9+CD4+ T cells and the cytokines influencing IL-9 production in paediatric visceral leishmaniasis.

The higher frequency of IL-9+CD4+ T cells and its decline following treatment implies their roles in the immunopathogenesis of VL; however, at the diagnosis onset, lower levels of serum IL-9 and its higher level in the culture supernatant may confer in vivo dysfunction of IL-9+CD4+ T cells in the acute phase of human VL.