IL-12 production by LC may actually be down-regulated, as reported to occur in susceptible strains of mice after infection with L. major (Moll et al., 2002), although intriguingly, ligation of CD154 on LCs is reported to stimulate IL-12p40 production (Sugaya et al., 2005) and may explain the up-regulation of IL-12p40 release by skin biopsies following anti-CD40 mAb treatment of CD154−/− mice exposed to the RA schistosome vaccine (Hewitson et al., 2006). The gene discussed is CD40; the disease is infection.