The role of interleukin-4 receptor alpha on smooth muscle cells during helminth infection

Includes abstract.Includes bibliographical references (leaves 101-111).Interleukin-4 receptor alpha (IL-4Ra) signaling, mediated by the ligands IL-4 and IL- 13, is important for effective host protection during murine Nippostrongylus brasiliensis (N. brasiliensis) and Schistosoma mansoni (S. manson!) infection. Among other cell types, IL-4Ra responsive smooth muscle cells influence immunological responses and are needed for host protection during N. brasiliensis and S. mansoni infection

Nippostrongylus-induced intestinal hypercontractility requires IL-4 receptor alpha-responsiveness by T cells in mice

Gut-dwelling helminthes induce potent IL-4 and IL-13 dominated type 2 T helper cell (T H 2) immune responses, with IL-13 production being essential for Nippostrongylus brasiliensis expulsion. This T H 2 response results in intestinal inflammation associated with local infiltration by T cells and macrophages. The resulting increased IL-4/IL-13 intestinal milieu drives goblet cell hyperplasia, alternative macrophage activation and smooth muscle cell hypercontraction. In this study we investigated how IL-4-promoted T cells contributed to the parasite induced effects in the intestine. This was achieved using pan T cell-specific IL-4 receptor alpha-deficient mice (iLck cre IL-4Rα −/lox ) and IL-4Rα-responsive control mice. Global IL-4Rα −/− mice showed, as expected, impaired type 2 immunity to N. brasiliensis . Infected T cell-specific IL-4Rα-deficient mice showed comparable worm expulsion, goblet cell hyperplasia and IgE responses to control mice. However, impaired IL-4-promoted T H 2 cells in T cell-specific IL-4Rα deficient mice led to strikingly reduced IL-4 production by mesenteric lymph node CD4 + T cells and reduced intestinal IL-4 and IL-13 levels, compared to control mice. This reduced IL-4/IL-13 response was associated with an impaired IL-4/IL-13-mediated smooth muscle cell hypercontractility, similar to that seen in global IL-4Rα −/− mice. These results demonstrate that IL-4-promoted T cell responses are not required for the resolution of a primary N. brasiliensis infection. However, they do contribute significantly to an important physiological manifestation of helminth infection; namely intestinal smooth muscle cell-driven hypercontractility

IL-4R{alpha}-responsive smooth muscle cells increase intestinal hypercontractility and contribute to resistance during acute Schistosomiasis.

Interleukin-(IL)-4 and IL-13 signal through heterodimeric receptors containing a common IL-4 receptor-alpha (IL-4Ralpha) subunit, which is important for protection against helminth infections, including schistosomiasis. Previous studies demonstrated important roles for IL-4Ralpha-responsive hematopoietic cells, including T cells and macrophages in schistosomiasis. In this study, we examined the role of IL-4Ralpha responsiveness by nonhematopoietic smooth muscle cells during experimental acute murine schistosomiasis. Comparative Schistosoma mansoni infection studies with smooth muscle cell-specific IL-4Ralpha-deficient (SM-MHC(cre)IL-4Ralpha(-/flox)) mice, heterozygous control (IL-4Ralpha(-/flox)) mice, and global IL-4Ralpha-deficient (IL-4Ralpha(-/-)) mice were conducted. S. mansoni-infected SM-MHC(cre)IL-4Ralpha(-/flox) mice showed increased weight loss and earlier mortalities compared with IL-4Ralpha(-/flox) mice, despite comparable T(H)2/type 2 immune responses. In contrast to highly susceptible IL-4Ralpha-deficient mice, increased susceptibility in SM-MHC(cre)IL-4Ralpha(-/flox) mice was not accompanied by intestinal tissue damage and subsequent sepsis. However, both susceptible mutant mouse strains failed to efficiently expel eggs, demonstrated by egg reduction in the feces compared with control mice. Reduced egg expulsion was accompanied by impaired IL-4/IL-13-mediated hypercontractile intestinal responses, which was present in the more resistant control mice. Together, we conclude that IL-4Ralpha responsiveness by smooth muscle cells and subsequent IL-4- and IL-13-mediated hypercontractility are required for host protection during acute schistosomiasis to efficiently expel S. mansoni eggs and to prevent premature mortality

<i>N. brasiliensis</i> induced smooth muscle cell hypertrophy/hyperplasia is unaffected in iLck^creIL-4Rα^−/lox mice.

<p>Haematoxylin and eosin stained sections were used to determine the smooth muscle cell layer thickness from Day 3, 7 and 10 <i>N. brasiliensis-</i>infected iLck^creIL-4Rα^−/lox and control mice. Representative photomicrographs are shown from control mice at days 3, 7 and 10 at 40× magnification. Also shown is a photomicrograph at 200× showing the longitudinal and circular smooth muscle layers included in the measurement (A). Measurements are shown in a bar graph (B) with mean values+SEM and represent 2 independent experiments with n = 4 or 5 mice per group. Ns = not significant. One-Way-ANOVA, ***<i>P<.001</i>.</p

IL-4 responsive T cells are not needed for expulsion of <i>N. brasiliensis.</i>

<p>iLck^creIL-4Rα^−/lox and control mice were infected with 750 <i>N. brasiliensis</i> L3 larvae. Faeces were collected from day 6 to 14 post infection (PI) and egg production was calculated using the modified McMaster technique (A). At days 7 and 10 PI the worm burden in the small intestine was assessed (pooled from 3 experiments) (B). Intestinal goblet cell hyperplasia was assessed by determining the total number of PAS-positive goblet cells per 5 villi in histological sections of the small intestine at day 7 and 10 PI (C). Mucus and PAS staining at days 7 and 10 PI. Representative photomicrographs are shown from individual mice and <i>N. brasiliensis</i> is indicated with a black arrow (D). Total IgE production in the serum was measured by ELISA at day 7 and 10 PI (E). The graphs show mean values ± SEM and represent the results of three independent experiments, except B and E where 2–3 independent experiments were combined with n = 4 or 5 mice per group. ND, not detected. One-Way-ANOVA, *<i>P<.05</i>, **<i>P<.01</i>, ***<i>P<.001</i> for all experiments.</p

Reduced IL-4 response in <i>N. brasiliensis-</i>infected iLck^creIL-4Rα^−/lox and IL-4Rα^−/− mice.

<p>Mice were infected with 750 <i>N. brasiliensis</i> L3 larvae and at days 7 and 10 PI CD4⁺ cells from pooled mesenteric lymph nodes were isolated by negative selection (purity>90%) then restimulated with anti-CD3 for 48 hours and IL-4, IL-13, INF-γ, IL-17 cytokine concentration of the supernatant determined by ELISA (A). Further, IL-4 and IL-13 concentrations were determined in homogenates of the jejunum (B). The graphs show mean values+SEM and are representative of the results of three independent experiments with IL-17 only determined in one experiment for CD4⁺ T cells and IL-13 in two independent experiments for homogenates, with n = 4 or 5 per group. One-Way-ANOVA, *<i>P<.05</i>, **<i>P<.01</i>, ***<i>P<.001</i>.</p