BACKGROUND
interleukin - <dig> and il- <dig> are related cytokines and the dominant mediators of th <dig> immune responses  <cit> .
signalling by both cytokines is dependent on binding to heterodimeric receptors containing the il- <dig> receptor α chain .
ligand binding results in intracellular signalling pathways activating the th <dig> defining transcription factors stat- <dig> and/or gata- <dig>  <cit> .
this polarisation to a th <dig> immune response is essential for the successful resolution of a number of helminth infections  <cit> .
actual worm expulsion, in nematode infections, is associated with increased il-13/il-4rα/stat- <dig> dependent intestinal smooth muscle contractions, epithelial cell turnover and goblet cell hyperplasia  <cit> .
infections of il-4-/-, il-13-/-, il-4rα-/- and stat 6-/- mice with the nematodes trichuris muris, heligmosomoides polygyrus and nippostrongylus brasiliensis have demonstrated a positive relationship between polarisation to a th <dig> immune response, goblet cell hyperplasia and worm expulsion  <cit> .
in support of a role for goblet cell derived mucus in worm expulsion in vitro experiments have demonstrated increased viscosity of mileu surrounding n. brasiliensis at an equivalent density to intestinal mucus inhibits worm movement  <cit> .
moreover, isolation of the goblet cell secreted protein relmβ/fizz <dig> and incubation with parasitic nematodes in vitro results in impaired chemotactic function in the worm  <cit> .
these observations have led to th <dig> induced goblet cell hyperplasia being considered a key mechanistic factor in resolving gastrointestinal related nematode infections  <cit>
intestinal goblet cell hyperplasia in schistosoma mansoni  infections is driven by parasite eggs traversing the intestine  <cit> , as opposed to nematode infections where adult worms residing in the intestine induce the goblet cell responses  <cit> .
s. mansoni eggs produced by adults residing in the mesenteric venules move from the blood vessels through the intestine passing to the lumen.
this movement of eggs generates considerable tissue damage as well as inducing a strong mucosal response in the intestine  <cit> .
as with nematode infections, s. mansoni induced mucus production has been considered to be th <dig> dependant  <cit> .
in this study we examined goblet cell hyperplasia in response to infection with the nematodes n. brasiliensis and syphacia obvelata and the trematode s. mansoni.
as already published n. brasiliensis infection induced a goblet cell hyperplasic response dependent on il-4/il-13/il-4rα expression  <cit> .
however, infection with the nematode s. obvelata did not increase goblet cell hyperplasia in the host colon, irrespective of il-4rα expression.
such data demonstrates that il-4rα driven goblet cell hyperplasia may not be essential for the clearance of all gastro-intestinal nematode infections.
furthermore, we also show s. mansoni induced goblet cell hyperplasia to be independent of il-4/il- <dig> responsiveness.
this data represents the first demonstration of goblet cell hyperplasia and mucus production in response to helminth infections being independent of il-4/il- <dig>
RESULTS
n. brasiliensis infection induces il-4/il- <dig> dependent goblet cell hyperplasia while s. obvelata infection does not induce goblet cell hyperplasia
examination of il-4/il- <dig> dependent goblet cell hyperplasic responses in the intestinal niches utilised by the nematodes n. brasiliensis and s. obvelata infections was carried out in balb/c, il-4/il-13-/-, il-4-/- and il-4rα-/- mice.
n. brasiliensis infected balb/c mice demonstrated significantly higher levels of goblet cell hyperplasia in the small intestine at both days  <dig> and  <dig> post infection  when compared to naïve mice .
however, no significant increase in the number of goblet cells in the intestine could be detected in infected and naïve il-4/il-13-/- or il4rα-/- mice when compared to naïve controls .
examination of intestinal worm burdens in balb/c mice showed resolution of infection by day  <dig> pi.
both il-4/il-13-/- and il-4rα-/- mice failed to expel adult worms by day  <dig> pi .
these data confirm n. brasiliensis clearance to be associated with an il-4/13/il-4rα dependent goblet cell hyperplasia.
s. obvelata adult worm burdens in infected wild type mice are only detectable by day  <dig> pi , this burden peaks by day  <dig> pi to approximately  <dig> worms/caecum.
infection of il-4rα-/- mice results in considerably higher worm burdens  when compared to wild type mice  <cit> .
in contrast to n. brasiliensis infected mice, no induction of goblet cell hyperplasia in the colon of s. obvelata infected balb/c, il-4rα-/- and il-4-/- mice was seen .
this lack of a goblet cell response was irrespective of heightened levels of the th <dig> cytokine il- <dig> at day  <dig> pi  in balb/c restimulated splenocytes isolated from infected mice  balb/c il- <dig> levels declined to that found in naïve mice at day  <dig> pi.
il-4rα-/- mice failed to demonstrate any significant increase in il- <dig> production when compared to naïve mice.
together these data demonstrate that s. obvelata infections do not induce a colonic mucus response even though levels of il- <dig> and other th <dig> cytokines are significantly increased  <cit>
schistosoma mansoni induces goblet cell hyperplasia in the intestine in an il-4/il- <dig> independent manner
s. mansoni infection induces a strong th <dig> immune response and goblet cell hyperplasia related to parasite egg production  <cit>  in order to confirm the role of parasite eggs in induction of goblet cell hyperplasia, we analysed the hyperplasic response at  <dig> weeks pi  and at the peak of parasite egg production;  <dig> weeks pi.
while no difference in the number of goblet cells could be detected in the intestine of naïve or infected balb/c at  <dig> weeks pi , a strong induction of goblet cell hyperplasia was detected at  <dig> weeks pi .
to establish whether this hyperplasic response was dependent on il-4/il-13/il-4rα responsiveness we examined the intestines of infected il-4/il-13-/- and il-4rα-/- mice at  <dig> weeks pi.
here we found no difference in the numbers of eggs accumulating in the small intestine and large intestine between balb/c, il-4/il-13-/- and il-4rα-/- mice .
goblet cell hyperplasia in the small intestine of all infected mouse groups was significantly elevated above naïve controls  and 3c).
furthermore, equivalent levels of goblet cell hyperplasia were found in the intestine of all infected mice groups .
to demonstrate if il-4/il-13/il-4rα independent goblet cell hyperplasia occurred throughout the intestine we also examined the colon of both naïve and infected mice.
as with the small intestine goblet cell hyperplasia was elevated above naïve controls in all mouse groups and no differences were found between infected groups .
together these results demonstrate il-4/il-13/il-4rα independent goblet cell hyperplasia in the intestine of mice infected with s. mansoni.
discussion
our data demonstrates that  goblet cell hyperplasia is dependent on helminth species and  il-4/il- <dig> responsiveness is not required for induction of s. mansoni egg induced goblet cell hyperplasia.
it has previously been demonstrated that n. brasiliensis  <cit>  and s. obvelata  <cit>  infected il-4-/-, il-13-/- and il-4rα-/- mice have impaired worm expulsion, while in s. mansoni infections il-4/il- <dig> signalling is essential for host survival  <cit> .
a common feature of both n. brasiliensis and s. mansoni infections is the hosts' goblet cell hyperplasic response to the parasite.
such responses have previously been considered to be dependent, in part at least, on the hosts th <dig> polarised immune response  <cit> .
from the data presented here and in other studies this does indeed appear to be the case in n. brasiliensis infections <cit> .
work on other parasitic nematode models such a t. muris also show a th <dig> dependent worm expulsion and goblet cell response  <cit> .
however, in this study we have demonstrated that this may not be the case for all intestinal nematode infections.
following oral infection with s. obvelata eggs, larvae emerge in the hosts small intestine at  <dig> day pi  <cit> .
from here the larvae migrate, mature and establish the definitive infection in the hosts cecum and colon.
we found the hosts th <dig> immune response to peak at day  <dig> pi and then decreases from at least day  <dig> pi.
previous work has shown that by day  <dig> pi this response is undetectable  <cit> .
together, these data demonstrate a transient th <dig> response to this infection.
th <dig> responses in other intestinal nematode infections result in strong goblet cell hyperplasic responses  <cit> .
however, mice infected with s. obvelata failed to generate hyperplasic goblet cell responses, suggesting that th <dig> induction of intestinal mucus responses is not a common feature of intestinal nematode infections, or that the th <dig> response needs to be sustained.
other factors such as prostaglandins  <cit> , cholinergic  <cit>  and non-cholinergic  <cit>  agonist may also play a role.
additionally, the different niches occupied by various species of parasitic nematodes could effect the host response to them  <cit> .
s. obvelata infections do not cause major pathology in the intestine  <cit>  as opposed to n. brasiliensis and t. muris which cause considerable histological damage to the hosts intestinal architecture  <cit> .
such differences in worm pathogenicity may explain the lack of a goblet cell response in s. obvelata infections, irrespective of the hosts th <dig> polarisation  <cit> .
s. mansoni infection induces a strong th <dig> response initiated by worm egg production at week  <dig> pi and persists throughout the infection  <cit> .
associated with this are significant levels of goblet cell hyperplasia in the intestine  <cit> .
s. mansoni egg antigens have previously been shown to also induce goblet cell hyperplasia in the lung in a il-4rα dependent manner  <cit> .
however the role of il-4rα in goblet cell hyperplasia in the intestine during the live infection has not been shown.
an explanation for the il-4rα independent hyperplasia described here could be the mode of s. mansoni infection and its interaction with the hosts' tissue.
s. mansoni eggs cause pathology from the adventitial surface of the intestine, as opposed to nematodes driving the pathology from the lumen.
we propose that the severe tissue damage resulting from the eggs migration from the adventitial surface to the lumen is capable of initiating a goblet cell response, independently of il- <dig> and il- <dig> signalling during s. mansoni infection.
in addition to il-4/il- <dig> other cytokines may act to induce goblet cells hyperplasia.
il- <dig> and il- <dig> have previously been shown to play a role in directly inducing il-4/il- <dig> independent goblet cell hyperplasia in lung models  <cit> .
il- <dig> overexpressing transgenic mice infected with s. mansoni do have increased goblet cell hyperplasia  <cit> .
however il- <dig> transgenic mice also had increased il- <dig> and il- <dig> compared to wild type mice, and therefore it cannot be concluded that il- <dig> directly increases goblet cell hyperplasia.
furthermore il- <dig> levels are decreased in n. brasiliensis infected il-4rα-/- mice  <cit> .
as such il-4/il- <dig> independent intestinal goblet cell hyperplasia may not be due to increased il- <dig>  no clear reports linking il- <dig> to goblet cell hyperplasia during s. mansoni infection have reported.
as il-4rα-/- mice have decreased il- <dig> expression it is also unlikely that il- <dig> induces intestinal goblet cell hyperplasia in s. mansoni infections  <cit> .
CONCLUSIONS
our results demonstrate for the first time that intestinal goblet cell hyperplasia in response to parasitic helminth infections can occur independently of il-4/il- <dig> signalling and that intestinal nematode infections may not always induce a goblet cell response.

 interleukin - and il- are related cytokines and the dominant mediators of th immune responses. signalling by both cytokines is dependent on binding to heterodimeric receptors containing the il- receptor α chain. ligand binding results in intracellular signalling pathways activating the th defining transcription factors stat- and/or gata-. this polarisation to a th immune response is essential for the successful resolution of a number of helminth infections. actual worm expulsion, in nematode infections, is associated with increased il-13/il-4rα/stat- dependent intestinal smooth muscle contractions, epithelial cell turnover and goblet cell hyperplasia. infections of il-4-/-, il-13-/-, il-4rα-/- and stat 6-/- mice with the nematodes trichuris muris, heligmosomoides polygyrus and nippostrongylus brasiliensis have demonstrated a positive relationship between polarisation to a th immune response, goblet cell hyperplasia and worm expulsion. in support of a role for goblet cell derived mucus in worm expulsion in vitro experiments have demonstrated increased viscosity of mileu surrounding n. brasiliensis at an equivalent density to intestinal mucus inhibits worm movement. moreover, isolation of the goblet cell secreted protein relmβ/fizz and incubation with parasitic nematodes in vitro results in impaired chemotactic function in the worm. these observations have led to th induced goblet cell hyperplasia being considered a key mechanistic factor in resolving gastrointestinal related nematode infections intestinal goblet cell hyperplasia in schistosoma mansoni infections is driven by parasite eggs traversing the intestine, as opposed to nematode infections where adult worms residing in the intestine induce the goblet cell responses. s. mansoni eggs produced by adults residing in the mesenteric venules move from the blood vessels through the intestine passing to the lumen. this movement of eggs generates considerable tissue damage as well as inducing a strong mucosal response in the intestine. as with nematode infections, s. mansoni induced mucus production has been considered to be th dependant. in this study we examined goblet cell hyperplasia in response to infection with the nematodes n. brasiliensis and syphacia obvelata and the trematode s. mansoni. as already published n. brasiliensis infection induced a goblet cell hyperplasic response dependent on il-4/il-13/il-4rα expression. however, infection with the nematode s. obvelata did not increase goblet cell hyperplasia in the host colon, irrespective of il-4rα expression. such data demonstrates that il-4rα driven goblet cell hyperplasia may not be essential for the clearance of all gastro-intestinal nematode infections. furthermore, we also show s. mansoni induced goblet cell hyperplasia to be independent of il-4/il- responsiveness. this data represents the first demonstration of goblet cell hyperplasia and mucus production in response to helminth infections being independent of il-4/il-  n. brasiliensis infection induces il-4/il- dependent goblet cell hyperplasia while s. obvelata infection does not induce goblet cell hyperplasia examination of il-4/il- dependent goblet cell hyperplasic responses in the intestinal niches utilised by the nematodes n. brasiliensis and s. obvelata infections was carried out in balb/c, il-4/il-13-/-, il-4-/- and il-4rα-/- mice. n. brasiliensis infected balb/c mice demonstrated significantly higher levels of goblet cell hyperplasia in the small intestine at both days and post infection when compared to naïve mice. however, no significant increase in the number of goblet cells in the intestine could be detected in infected and naïve il-4/il-13-/- or il4rα-/- mice when compared to naïve controls. examination of intestinal worm burdens in balb/c mice showed resolution of infection by day pi. both il-4/il-13-/- and il-4rα-/- mice failed to expel adult worms by day pi. these data confirm n. brasiliensis clearance to be associated with an il-4/13/il-4rα dependent goblet cell hyperplasia. s. obvelata adult worm burdens in infected wild type mice are only detectable by day pi, this burden peaks by day pi to approximately worms/caecum. infection of il-4rα-/- mice results in considerably higher worm burdens when compared to wild type mice. in contrast to n. brasiliensis infected mice, no induction of goblet cell hyperplasia in the colon of s. obvelata infected balb/c, il-4rα-/- and il-4-/- mice was seen. this lack of a goblet cell response was irrespective of heightened levels of the th cytokine il- at day pi in balb/c restimulated splenocytes isolated from infected mice balb/c il- levels declined to that found in naïve mice at day pi. il-4rα-/- mice failed to demonstrate any significant increase in il- production when compared to naïve mice. together these data demonstrate that s. obvelata infections do not induce a colonic mucus response even though levels of il- and other th cytokines are significantly increased schistosoma mansoni induces goblet cell hyperplasia in the intestine in an il-4/il- independent manner s. mansoni infection induces a strong th immune response and goblet cell hyperplasia related to parasite egg production in order to confirm the role of parasite eggs in induction of goblet cell hyperplasia, we analysed the hyperplasic response at weeks pi and at the peak of parasite egg production; weeks pi. while no difference in the number of goblet cells could be detected in the intestine of naïve or infected balb/c at weeks pi, a strong induction of goblet cell hyperplasia was detected at weeks pi. to establish whether this hyperplasic response was dependent on il-4/il-13/il-4rα responsiveness we examined the intestines of infected il-4/il-13-/- and il-4rα-/- mice at weeks pi. here we found no difference in the numbers of eggs accumulating in the small intestine and large intestine between balb/c, il-4/il-13-/- and il-4rα-/- mice. goblet cell hyperplasia in the small intestine of all infected mouse groups was significantly elevated above naïve controls and 3c). furthermore, equivalent levels of goblet cell hyperplasia were found in the intestine of all infected mice groups. to demonstrate if il-4/il-13/il-4rα independent goblet cell hyperplasia occurred throughout the intestine we also examined the colon of both naïve and infected mice. as with the small intestine goblet cell hyperplasia was elevated above naïve controls in all mouse groups and no differences were found between infected groups. together these results demonstrate il-4/il-13/il-4rα independent goblet cell hyperplasia in the intestine of mice infected with s. mansoni. discussion our data demonstrates that goblet cell hyperplasia is dependent on helminth species and il-4/il- responsiveness is not required for induction of s. mansoni egg induced goblet cell hyperplasia. it has previously been demonstrated that n. brasiliensis and s. obvelata infected il-4-/-, il-13-/- and il-4rα-/- mice have impaired worm expulsion, while in s. mansoni infections il-4/il- signalling is essential for host survival. a common feature of both n. brasiliensis and s. mansoni infections is the hosts' goblet cell hyperplasic response to the parasite. such responses have previously been considered to be dependent, in part at least, on the hosts th polarised immune response. from the data presented here and in other studies this does indeed appear to be the case in n. brasiliensis infections. work on other parasitic nematode models such a t. muris also show a th dependent worm expulsion and goblet cell response. however, in this study we have demonstrated that this may not be the case for all intestinal nematode infections. following oral infection with s. obvelata eggs, larvae emerge in the hosts small intestine at day pi. from here the larvae migrate, mature and establish the definitive infection in the hosts cecum and colon. we found the hosts th immune response to peak at day pi and then decreases from at least day pi. previous work has shown that by day pi this response is undetectable. together, these data demonstrate a transient th response to this infection. th responses in other intestinal nematode infections result in strong goblet cell hyperplasic responses. however, mice infected with s. obvelata failed to generate hyperplasic goblet cell responses, suggesting that th induction of intestinal mucus responses is not a common feature of intestinal nematode infections, or that the th response needs to be sustained. other factors such as prostaglandins, cholinergic and non-cholinergic agonist may also play a role. additionally, the different niches occupied by various species of parasitic nematodes could effect the host response to them. s. obvelata infections do not cause major pathology in the intestine as opposed to n. brasiliensis and t. muris which cause considerable histological damage to the hosts intestinal architecture. such differences in worm pathogenicity may explain the lack of a goblet cell response in s. obvelata infections, irrespective of the hosts th polarisation. s. mansoni infection induces a strong th response initiated by worm egg production at week pi and persists throughout the infection. associated with this are significant levels of goblet cell hyperplasia in the intestine. s. mansoni egg antigens have previously been shown to also induce goblet cell hyperplasia in the lung in a il-4rα dependent manner. however the role of il-4rα in goblet cell hyperplasia in the intestine during the live infection has not been shown. an explanation for the il-4rα independent hyperplasia described here could be the mode of s. mansoni infection and its interaction with the hosts' tissue. s. mansoni eggs cause pathology from the adventitial surface of the intestine, as opposed to nematodes driving the pathology from the lumen. we propose that the severe tissue damage resulting from the eggs migration from the adventitial surface to the lumen is capable of initiating a goblet cell response, independently of il- and il- signalling during s. mansoni infection. in addition to il-4/il- other cytokines may act to induce goblet cells hyperplasia. il- and il- have previously been shown to play a role in directly inducing il-4/il- independent goblet cell hyperplasia in lung models. il- overexpressing transgenic mice infected with s. mansoni do have increased goblet cell hyperplasia. however il- transgenic mice also had increased il- and il- compared to wild type mice, and therefore it cannot be concluded that il- directly increases goblet cell hyperplasia. furthermore il- levels are decreased in n. brasiliensis infected il-4rα-/- mice. as such il-4/il- independent intestinal goblet cell hyperplasia may not be due to increased il- no clear reports linking il- to goblet cell hyperplasia during s. mansoni infection have reported. as il-4rα-/- mice have decreased il- expression it is also unlikely that il- induces intestinal goblet cell hyperplasia in s. mansoni infections.  our results demonstrate for the first time that intestinal goblet cell hyperplasia in response to parasitic helminth infections can occur independently of il-4/il- signalling and that intestinal nematode infections may not always induce a goblet cell response. 
intestinal mucus production by hyperplasic goblet cells is a striking pathological feature of many parasitic helminth infections and is related to intestinal protection and worm expulsion. furthermore, induction of goblet cell hyperplasia in response to s. mansoni eggs traversing the intestine was equivalent between balb/c, il-4/il-13-/- and il-4rα-/- mice. induction of goblet cell hyperplasia is associated with th immune responses, which in helminth infections are controlled primarily by il- and also il- in the study presented here we examine the goblet cell hyperplasic response to three experimental parasitic helminth infections; namely nippostrongylus brasiliensis, syphacia obvelata and schistosoma mansoni. together these data demonstrate that intestinal goblet cell hyperplasia can be independent of th immune responses associated with parasitic helminth infections. as expected n. brasiliensis infection induced a strong goblet cell hyperplasia dependent on il-4/il-13/il-4rα expression. in contrast, and despite previously published transiently elevated il-4/il- levels, s. obvelata infections did not increase goblet cell hyperplasia in the colon.
 intestinal mucus production by hyperplasic goblet cells is a striking pathological feature of many parasitic helminth infections and is related to intestinal protection and worm expulsion. induction of goblet cell hyperplasia is associated with th immune responses, which in helminth infections are controlled primarily by il- and also il- in the study presented here we examine the goblet cell hyperplasic response to three experimental parasitic helminth infections; namely nippostrongylus brasiliensis, syphacia obvelata and schistosoma mansoni.  as expected n. brasiliensis infection induced a strong goblet cell hyperplasia dependent on il-4/il-13/il-4rα expression. in contrast, and despite previously published transiently elevated il-4/il- levels, s. obvelata infections did not increase goblet cell hyperplasia in the colon. furthermore, induction of goblet cell hyperplasia in response to s. mansoni eggs traversing the intestine was equivalent between balb/c, il-4/il-13-/- and il-4rα-/- mice.  together these data demonstrate that intestinal goblet cell hyperplasia can be independent of th immune responses associated with parasitic helminth infections. 