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

Resistance and susceptibility to the intestinal nematode Trichuris mur is 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 domi nant T(h)2 response, sub-threshold levels of infection (< 40 eggs) can survive and become sexually mature adult worms (10-20 adults). The im munological basis of this phenomenon was found to be a dramatically al tered polarization of the CD4 response. The T(h)2-response characteris tic of this strain of mouse infected with T. muris was shown to be sig nificantly 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 presenc e of parasite-specific IgG2a were greatly up-regulated in these mice.