LOW-LEVEL INFECTION WITH TRICHURIS-MURIS SIGNIFICANTLY AFFECTS THE POLARIZATION OF THE CD4 RESPONSE

Resistance and susceptibility to the intestinal nematode Trichuris muris has been shown to be dependent upon the induction of Thelper type 2 (T(h)2) or T(h)1 cells, respectively. This study demonstrates that in a normally resistant strain of mouse, i.e. BALB/K which mounts a dominant T(h)2 response, sub-threshold levels of infection (< 40 eggs) can survive and become sexually mature adult worms (10-20 adults). The immunological basis of this phenomenon was found to be a dramatically altered polarization of the CD4 response. The T(h)2-response characteristic of this strain of mouse infected with T. muris was shown to be significantly down-regulated as assessed by in vitro cytokine production [interleukin (IL)-4, IL-5 and IL-9]. In contrast, T(h)1 parameters of infection such as in vitro interferon-gamma production and the presence of parasite-specific IgG2a were greatly up-regulated in these mice.