Neither interleukin-4 receptor alpha expression on CD4+ T cells, or macrophages and neutrophils is required for protective immunity to Trichinella spiralis

Abstract

The T helper type 2 (Th2) mediated expulsion of the gastrointestinal nematode Trichinella spiralis requires interleukin-4 receptor alpha (IL-4Ralpha) expression on both bone-marrow-derived and non-bone-marrow-derived cells. To more definitively investigate the role of IL-4/IL-13 responsiveness in the development of protective immunity to T. spiralis, cell-specific IL-4Ralpha signalling on CD4(+) T cells (Lck(cre) IL-4Ralpha(-/flox)) and macrophages/neutrophils (LysM(cre) IL-4Ralpha(-/flox)) was analysed on the BALB/c background. Infection of wild-type and control IL-4Ralpha(-/flox) mice induced a Th2-type immune response with elevated IL-4 cytokine production, parasite-specific immunoglobulin G1 (IgG1), total IgE, intestinal mastocytosis and enteropathy. In contrast, global IL-4Ralpha-deficient BALB/c mice showed reduced worm expulsion, antibody production, intestinal mastocytosis and gut pathology. BALB/c mice generated with cell-specific deletion of IL-4Ralpha on CD4(+) T lymphocytes or macrophages/neutrophils, controlled gastrointestinal helminth infection by eliciting a protective immune response comparable to that observed with wild-type and IL-4Ralpha(-/flox) controls. Together, this shows that the development of host protective Th2 responses accompanied by parasite loss is independent of IL-4Ralpha expression on CD4(+) T cells and macrophages/neutrophils.

Figure 1

Expulsion of Trichinella spiralis in mice deficient for interleukin-4 receptor α (IL-4Rα) expression on CD4⁺ T cells (Lck^cre IL-4Rα^−/flox). Establishment and expulsion of T. spiralis was measured in (a) IL-4Rα^−/flox (BALB/c wild-type, bearing one floxed and one disrupted IL-4Rα allele), (b) global IL-4Rα^−/− and (c) Lck^cre IL-4Rα^−/flox mice at days 6 and 16 postinfection. Adult T. spiralis worms were recovered from excised intestine to determine the total worm numbers per strain. Data are expressed as the mean worm burden ±SEM. Four mice were used per group. *P< 0·05, significantly different from day 6 postinfection.

Figure 2

Mice expel Trichinella spiralis in the absence of interleukin-4 (IL-4)/IL-13-responsive macrophages/neutrophils. (a) BALB/c wild-type and (b) LysM^cre IL-4Rα^−/flox mice were infected with 400 freshly isolated T. spiralis larvae and their worm burden was monitored at days 6 and 14 postinfection. Data are expressed as the mean worm burden ± SEM. Four mice were used per group. *P < 0·05, significantly different from day 6 postinfection.

Figure 3

The development of villus atrophy and crypt hyperplasia was measured in (a) interleukin-4 receptor α (IL-4Rα)^−/flox, (b) IL-4Rα^−/−, (c) Lck^cre IL-4Rα^−/flox, (d) BALB/c and (e) LysM^cre IL-4Rα^−/flox mice at days 0 and 6 postinfection. Data are expressed as mean length (in μm) + SEM. Three to five mice were used per group. *P < 0·05, significantly different from uninfected.

Figure 4

Deletion of interleukin-4 receptor α (IL-4Rα) on either CD4⁺ T cells or macrophages/neutrophils does not abrogate Trichinella spiralis-induced mastocytosis. Mast cell hyperplasia in response to the gastrointestinal nematode was measured in (a) IL-4Rα^−/flox, (b) IL-4Rα^−/−, (c) Lck^cre IL-4Rα^−/flox, (d) BALB/c and (e) LysM^cre IL-4Rα^−/flox mice. Carnoy’s-fixed jejuna from uninfected and infected (day 16 postinfection) mice were processed and stained with 0·5% toluidine blue and numbers of intestinal mast cells in 10 villus/crypt units (VCU) were counted. Data are expressed as the mean number of masts and/or villus/crypt units. Three to five mice were used per group. *P< 0·05, significantly different from uninfected; ψP < 0·05, significantly different from IL-4Rα^−/flox and Lck^cre IL-4Rα^−/flox.

Figure 5

Intraepithelial invading helminths elicit a T helper type 2 (Th2) immune response independent of interleukin-4Rα (IL-4Rα) signalling on either CD4⁺ T cells or macrophages/neutrophils. Sera and mesenteric lymph nodes were removed from uninfected and infected (day 6 postinfection) (a) IL-4Rα^−/flox, (b) global IL-4Rα^−/−, (c) Lck^cre IL-4Rα^−/flox, (d) BALB/c and (e) LysM^cre IL-4Rα^−/flox mice and analysed for antibody and cytokine responses. Parasite-specific IL-4, immunoglobulin G1 (IgG1) and total IgE were measured and the data expressed as the mean value + SEM. Three to five mice were used per group. *P< 0·05, significantly different from naïve; ψP < 0·05, significantly different from BALB/c IL-4Rα^−/flox and Lck^cre IL-4Rα^−/flox. ND, not detectable.