Earlier studies with IFN-γ−/− mice and B6.Jalpha281−/− mice (lacking NKT cells) have confirmed an absolute requirement for IFN-γ for sustained (24 h) expression of CXCL10 mRNA in L. donovani infection; an indispensable role for invariant NKT cells for the regulation of hepatic CXCL10 gene expression during the infection, because both CD3−NK1.1+ NK cells and CD3intNK1.1+ NKT cells are the early sources of IFN-γ production (Svensson et al., 2005). The gene discussed is CXCL10; the disease is infection.