Experimental RA was induced by the transfer of Th1-type DO11.10 CD4+ T cells in recipient BALB/c mice (RA), and after 6 weeks of infection with T. crassiceps (Tc + RA), control mice received unpolarized cells (Control), as well as the infected group (Tc); all groups were immunized with OVA in CFA followed by a periarticular injection near the ankle joints with HAO in both rear paws. This evidence concerns the gene CD4 and infection.