Nippostrongylus brasiliensis can induce B7-independent antigen-specific development of IL-4-producing T cells from naive CD4 T cells in vivo

Th2 immune responses to a number of infectious pathogens are dependent on B7-1/B7-2 costimulatory molecule interactions. We have now examined the Th2 immune response to Nippostrongylus brasiliensis (Nb) in B7-1/B7-2(-/-) mice and show that Th2 effector cells develop that can mediate worm expulsion and produce substantial Th2 cytokines comparable with wild-type infected mice; however, in marked contrast, B cell Ag-specific Ab production is abrogated after B7 blockade. To examine the mechanism of T cell activation, OVA-specific DO11.10 T cells were transferred to recipient mice, which were then immunized with a combination of Nb plus OVA or either alone. Only the combination of Nb plus OVA triggered T cell differentiation to OVA-specific Th2 cells, suggesting that Nb acts as an adjuvant to stimulate Ag-specific naive T cells to differentiate to effector Th2 cells. Furthermore, using the DO11.10 TCR-transgenic T cell adoptive transfer model, we show that blocking B7-1/B7-2 interactions does not impair nonparasite Ag-specific DO11.10 Th2 cell differentiation; however, DO11.10 T cell cycle progression and migration to the B cell zone are inhibited.     

Limited ability of antigen-specific Th1 responses to inhibit Th2 cell development in vivo

Th1 and Th2 cells mutually antagonize each other's differentiation. Consequently, allergen-specific Th1 cells are believed to be able to suppress the development of Th2 cells and to prevent the development of atopic disorders. To determine whether a pre-existing Ag-specific Th1 response can affect the development of Th2 cells in vivo, we used an immunization model of Ag-pulsed murine dendritic cell (DC) transfer to induce distinct Th responses. When transferred into naive mice, Ag-pulsed CD8alpha(+) DCs induced a Th1 response and the production of IgG2a, whereas CD8alpha(-) DCs primed a Th2 response and the production of IgE. In the presence of a pre-existing Ag-specific Th2 environment due to Ag-pulsed CD8alpha(-) DC transfer, CD8alpha(+) DCs failed to prime Th1 cells. In contrast, CD8alpha(-) DCs could prime a Th2 response in the presence of a pre-existing Ag-specific Th1 environment. Moreover, exogenous IL-4 abolished the Th1-inducing potential of CD8alpha(+) DCs in vitro, but the addition of IFN-gamma did not effectively inhibit the potential of CD8alpha(-) DCs to prime IL-4-producing cells. Thus, Th1 and Th2 cells differ in their potential to inhibit the development of the other. This suggests that the early induction of allergen-specific Th1 cells before allergy sensitization will not prevent the development of atopic disorders.     

B cells as antigen-presenting cells: antigen-specific IL-2 production by cloned T cells without expression of IL-2 receptors

A murine T cell clone, 24-2C, responds specifically to human IgG (HGG) in the context of I-Ab. B cells purified from mouse spleen cells were examined for their function as antigen-presenting cells (APC) in the response of 24-2C cells to HGG. B cells functioned as APC for IL-2 production but not for proliferation, whereas spleen cells or spleen-adherent cells functioned as APC for both IL-2 production and proliferation. LPS-activated B cells also failed to induce the proliferative response. The addition of the culture supernatant of 24-2C cells stimulated with HGG presented by irradiated spleen cells to the culture of 24-2C cells, irradiated B cells, and HGG induced the proliferative response of 24-2C cells, whereas IL-1, IL-3, and/or interferon-gamma did not reconstitute the proliferation. The expression of IL-2 receptors (IL-2R) on 24-2C cells was examined using a monoclonal anti-mouse IL-2R antibody AMT 13 or 7D4. 24-2C cells cultured with spleen cells as APC expressed IL-2R. Those cultured alone or with B cells as APC did not express IL-2R. Enlargement of 24-2C cells in response to HGG was also examined, and the relative cell size of those cultured with B cells or spleen cells as APC was larger than that of those cultured alone. These results demonstrate that B cells as APC induce IL-2 production and cell size enlargement in the response of 24-2C cloned T cells to HGG, but not IL-2R expression nor proliferation.     

Cutting edge: the development of IL-4-producing B cells (B effector 2 cells) is controlled by IL-4, IL-4 receptor alpha, and Th2 cells

Although IL-4-producing B cells (B effector 2 cells) are found following infection and immunization, the signals regulating IL-4 production by Be2 cells are unknown. We show that culturing naive B cells with Th2 cells induces up-regulation of IL-4 in the B cells with a concomitant down-regulation of T-bet, IL-12Rbeta2, and IFN-gamma. Up-regulation of IL-4 in the Be2 cells is dependent on both T cells and IL-4 as IL-4Ralpha-deficient B cells primed with Th2 cells did not transcribe IL-4, and B cells primed in the presence of IL-4-deficient Th2 cells produced IFN-gamma instead of IL-4. Likewise, the in vivo development of IL-4-expressing B cells in a nematode infection model was dependent on both T cells and IL-4Ralpha-mediated signals. Thus, the differentiation of naive B cells into IL-4-expressing Be2 cells is regulated by a combination of T cell-dependent signals and the cytokine environment and this process is critically dependent upon the IL-4/IL-4R signaling pathway.     

IL-4 from Th2-type cells suppresses induction of delayed-type hypersensitivity elicited shortly after immunization

The pure delayed-type hypersensitivity reaction obtained in 4-day ovalbumin-sensitized mice after antigen challenge in the footpad was abrogated by transfer of in vitro expanded, antigen-specific lymphoblasts derived from ovalbumin-hyperimmunized donors (high antibody producers), 12 h before immunization. This effect was specific inasmuch as Trypanosoma cruzi-specific blasts derived from Tc-Ag-hyperimmunized mice did not inhibit delayed-type hypersensitivity in ovalbumin-immunized recipients. The ovalbumin-specific blasts displayed a Th2 cytokine profile, secreting IL-4 and IL-10 upon restimulation in vitro with ovalbumin, but not IFN-gamma or IL-2. In addition, recipients of such cells produced much more IgG1 and IgE antibodies. When the frequency of T-cell blasts was enriched among these cells, transfer of four million cells was enough to prevent the induction of delayed-type hypersensitivity. Neutralization of IL-4 alone just before cell transfer not only restored the delayed-type hyper-sensitivity reaction, but also maintained it in a plateau for at least 72 h after challenge. Recipients treated in this way also showed a shift back towards a Th1 phenotype, indicated by the increase in IL-2, IFN-gamma and IL-12 synthesis. No synergistic action was observed when IL-4 and IL-10 were concomitantly neutralized. These results indicate that activation of Ag-specific Th2 cells early in the course of the immune response to a protein antigen provides an immunological environment rich in IL-4, thus leading to the inhibition of cell-mediated immunity.     

Regulatory roles of IL-2 and IL-4 in H4/inducible costimulator expression on activated CD4+ T cells during Th cell development

We found a tight correlation among the levels of H4/inducible costimulator (ICOS) expression, IL-4 production, and GATA-3 induction, using activated CD4(+) T cells obtained from six different murine strains. BALB/c-activated CD4(+) T cells expressed approximately 10-fold more H4/ICOS on their surfaces and produced approximately 10-fold more IL-4 upon restimulation than C57BL/6-activated CD4(+) T cells. BALB/c naive CD4(+) T cells were shown to produce much higher amounts of IL-2 and IL-4 upon primary stimulation than C57BL/6 naive CD4(+) T cells. Neutralization of IL-4 with mAbs in culture of BALB/c naive CD4(+) T cells strongly down-regulated both H4/ICOS expression on activated CD4(+) T cells and IL-4 production upon subsequent restimulation. Conversely, exogenous IL-4 added to the culture of BALB/c or C57BL/6 naive CD4(+) T cells up-regulated H4/ICOS expression and IL-4 production upon restimulation. In addition, retroviral expression of GATA-3 during the stimulation of naive CD4(+) T cells from C57BL/6 or IL-4(-/-) mice increased H4/ICOS expression on activated CD4(+) T cells. A similar effect of IL-2 in the primary culture of BALB/c naive CD4(+) T cells appeared to be mediated by IL-4, the production of which was regulated by IL-2. These data suggest that IL-4 induced by IL-2 is critical to the maintenance of high H4/ICOS expression on BALB/c-activated CD4(+) T cells.     

TCR-independent activation of extrathymically developed, self antigen-specific T cells by IL-2/IL-15

Naive intrathymically developed T cells, which express foreign Ag-specific TCR, do not express IL-2R. After antigenic stimulation, they express high affinity IL-2R, which enables IL-2 to be used as an autocrine growth factor. On the contrary, extrathymically developed T cells, which express self Ag-specific TCR but are unresponsive to antigenic stimulation, spontaneously express low affinity IL-2R. In this study, we compared the responses of these two subsets of T cells to IL-2R stimulation and examined the influences of TCR-mediated signaling on the responses. IL-2 or IL-15 augmented the proliferative response of Ag-stimulated, intrathymically developed T cells. On the other hand, extrathymically developed T cells proliferated in response to IL-2 or IL-15, independently of Ag stimulation. Furthermore, both IL-2 and IL-15 induced IFN-gamma production of these T cells, which is strikingly augmented by the presence of IL-12. These results revealed functional differences between intrathymically developed, foreign Ag-specific T cells and extrathymically developed, self Ag-specific T cells. The latter can be activated by some inflammatory cytokines, in an Ag-independent manner, similar to NK cells.     

Germinal center B cells constitute a predominant physiological source of IL-4: implication for Th2 development in vivo

Protective immunity depends upon the capability of the immune system to properly adapt the response to the nature of an infectious agent. CD4(+) Th cells are implicated in this orchestration by secreting a polarized pattern of cytokines. Although Th2 development in animal models and in human cells in vitro to a large extent depends on IL-4, the nature of the cells that provide the initial IL-4 in vivo is still elusive. In this report, we describe the anatomical localization as well as the identity of IL-4-producing cells in human tonsil, a representative secondary lymphoid organ. We demonstrate that IL-4 production is a normal and intrinsic feature of germinal center (GC) B cells. We also show that expression of IL-4 is highly confined to the GCs, in which the B cells constitute the prevalent cellular source. Furthermore, immunofluorescence analysis of colon mucosa reveals a strikingly similar pattern of IL-4-expressing cells compared with tonsils, demonstrating that IL-4 production from GC B cells is not a unique feature of the upper respiratory tract. Our results show that GCs provide the most appropriate microenvironment for IL-4-dependent Th2 polarization in vivo and imply a critical role for GC B cells in this differentiation process.     

Activation of antigen-specific CD4+ Th2 cells and B cells in vivo increases norepinephrine release in the spleen and bone marrow

The neurotransmitter norepinephrine (NE) binds to the beta 2-adrenergic receptor (beta 2AR) expressed on various immune cells to influence cell homing, proliferation, and function. Previous reports showed that NE stimulation of the B cell beta 2AR is necessary for the maintenance of an optimal primary and secondary Th2 cell-dependent Ab response in vivo. In the present study we investigated the mechanism by which activation of Ag-specific CD4+ Th2 cells and B cells in vivo by a soluble protein Ag increases NE release in the spleen and bone marrow. Our model system used scid mice that were reconstituted with a clone of keyhole limpet hemocyanin-specific Th2 cells and trinitrophenyl-specific B cells. Following immunization, the rate of NE release in the spleen and bone marrow was determined using [3H]NE turnover analysis. Immunization of reconstituted scid mice with a cognate Ag increased the rate of NE release in the spleen and bone marrow 18-25 h, but not 1-8 h, following immunization. In contrast, immunization of mice with a noncognate Ag had no effect on the rate of NE release at any time. The cognate Ag-induced increase in NE release was partially blocked by ganglionic blockade with chlorisondamine, suggesting a role for both pre- and postganglionic signals in regulating NE release. Thus, activation of Ag-specific Th2 cells and B cells in vivo by a soluble protein Ag increases the rate of NE release and turnover in the spleen and bone marrow 18-25 h after immunization.     

IL-4 plays a dominant role in the differential development of Tho into Th1 and Th2 cells.

We have analyzed the evolution of the pattern of lymphokine secretion by Th cell lines specific for either the synthetic terpolymer Glu60Ala30Tyr10 (GAT) or killed bacillus Calmette Guérin. When cultured in the presence of exogenous rIL-2 as a growth factor, GAT-specific Th cell lines secreted mainly IL-4, whereas bacillus Calmette Guérin-specific lines produced predominantly IL-2. However, culturing in the presence of rIL-4 or of anti-IL-4 mAb and rIL-2 led to the establishment of Th2-like and Th1-like lines, respectively, regardless of their Ag specificity. Inasmuch as we show that the proliferative response of mature Th1 and Th2 cells was identical in the presence of IL-4, these results indicate that IL-4 influences the development of Th cell subsets. To understand the mode of IL-4 action, we isolated immature GAT-specific Tho clones able to secrete IL-2 and IL-4. Two types of Tho cells were isolated: ThoA cells that secreted IL-2 and IL-4, but not IFN-gamma, and ThoB cells that secreted IL-2, IL-4, and IFN-gamma. We show for the first time that such cells are indeed Th precursors able to differentiate into Th1 or Th2 cells. We demonstrate that IL-4 positively and negatively controls the differentiation of Tho cells into Th2 and Th1 cells, respectively. When cultured in rIL-4, Tho cells stop secreting IL-2 and IFN-gamma, but maintain IL-4 secretion. Moreover, endogenous IL-4 produced by Tho cells has similar effects: when cultured in rIL-2 alone, Tho cells either keep their immature phenotype or become Th2 cells, but do not become Th1 cells. In contrast, neutralization of secreted IL-4 completely prevents the differentiation of Tho into Th2 cells, but permits the development of Th1 cells. The presence of exogenous IFN-gamma does not affect the development of Tho into Th1 and Th2 cells, because it does not modify either mode of IL-4 action. However, it influences the ratio between the two types of Tho cells: when IL-4 is neutralized, added IFN-gamma can induce IFN-gamma secretion by ThoA cells and thereby facilitate their passage into ThoB cells. Taken together, our results demonstrate that IL-4, in addition to mediating T cell growth, is a principal factor that controls the differential development of Tho cells into Th1 and Th2 cells.     

IL-33 induces antigen-specific IL-5+ T cells and promotes allergic-induced airway inflammation independent of IL-4

Type 2 cytokines (IL-4, IL-5, and IL-13) play a pivotal role in helminthic infection and allergic disorders. CD4(+) T cells which produce type 2 cytokines can be generated via IL-4-dependent and -independent pathways. Although the IL-4-dependent pathway is well documented, factors that drive IL-4-independent Th2 cell differentiation remain obscure. We report here that the new cytokine IL-33, in the presence of Ag, polarizes murine and human naive CD4(+) T cells into a population of T cells which produce mainly IL-5 but not IL-4. This polarization requires IL-1R-related molecule and MyD88 but not IL-4 or STAT6. The IL-33-induced T cell differentiation is also dependent on the phosphorylation of MAPKs and NF-kappaB but not the induction of GATA3 or T-bet. In vivo, ST2(-/-) mice developed attenuated airway inflammation and IL-5 production in a murine model of asthma. Conversely, IL-33 administration induced the IL-5-producing T cells and exacerbated allergen-induced airway inflammation in wild-type as well as IL-4(-/-) mice. Finally, adoptive transfer of IL-33-polarized IL-5(+)IL-4(-)T cells triggered airway inflammation in naive IL-4(-/-) mice. Thus, we demonstrate here that, in the presence of Ag, IL-33 induces IL-5-producing T cells and promotes airway inflammation independent of IL-4.     

Thymic modulation of IL-2 and IL-4 synthesis by peripheral T cells

In this paper we provide several lines of evidence to support the hypothesis that the thymus can exert regulatory influences on the functional capabilities of mature recirculating T cells. Our studies demonstrate that while the IL-2-producing potential of T cells that repopulate the secondary lymphoid organs of lethally irradiated and stem cell-reconstituted mice is significantly reduced compared to that of T cells harvested from normal mice, the amount of IL-4 produced by the T cells of these experimental animals is equivalent to, or greater than, the amount produced by T cells from control animals. In addition, we determined that the amount of biologically active IL-2 and IL-4 secreted by T cells harvested from lethally irradiated animals who reconstitute their hematopoietic and immune systems under the influence of nonirradiated thymic epithelial grafts is essentially identical to the amount produced by T cells harvested from nonirradiated control animals. Collectively, these findings suggest that: (1) the alterations observed in the lymphokine-producing potential of T cells harvested from lethally irradiated and stem cell-reconstituted mice is not due to a direct effect of ionizing radiation on the T lymphocytes themselves, and (2) the exposure of the epithelial cells of the thymus to ionizing radiation during marrow-ablative regimens abrogates or modifies a component of thymic function which can influence the lymphokine-secreting potential of recirculating T cells. Further evidence for thymic involvement in the regulation of lymphokine production by peripheral T cells comes from our finding of a post-thymectomy time-dependent reduction in the capacity of T cells from animals to produce IL-2. Coincident with this reduction, T cells harvested from peripheral lymphoid organs of thymectomized animals demonstrated an augmentation in their IL-4-producing capabilities. The finding that treatment of thymectomized animals with the androgen steroid hormone dehydroepiandrosterone reestablished a normal IL-2-producing potential by their T cells makes it unlikely that the reduced capacity to produce IL-2 was secondary to a loss in fresh thymic emigrants.     

IL-4 directs the development of Th2-like helper effectors

Our studies show that the presence of IL-4 during the response of naive Th cells causes precursors to develop into a population comprised largely of "Th2-like" effectors that secrete IL-4 and IL-5, but little IL-2 or IFN-gamma. We find that the levels of IL-4 and IL-2 determine both the level of effectors developed in response to mitogen or Ag and the patterns of lymphokines they secrete when restimulated. IL-2 is required for optimum generation of effectors, and increasing levels of IL-2, augments the expansion of effectors secreting both IL-4/IL-5 and IFN-gamma. In contrast, IL-4 is required for the development of IL-4/IL-5 secreting effectors but suppresses the development of IL-2 and at higher doses IFN-gamma-secreting effectors detected after 4 days. Also dramatic are the effects of the presence or absence of IL-4 evaluated after an additional 1 to 2 wk. When cultures with or without initial IL-4 are cultured in IL-2 alone from days 4 to 11, they retain their distinct patterns of lymphokine production. Those cells that developed in cultures without IL-4 progressively secrete more IL-2 and can be maintained and expanded in IL-2. They continue to produce IFN-gamma, though the levels decrease somewhat with time, but they do not acquire the ability to produce IL-4 or IL-5. These cells thus increasingly resemble Th1 cell lines. In contrast, those cells in cultures initially exposed to IL-4, generate effectors which secrete high levels of IL-4/IL-5 (plus variable levels of IFN-gamma) at days 4 to 5, but the populations of cells developed, are not maintained well on IL-2 alone. Those cells that do survive continue to secrete IL-4 and IL-5 but not IL-2. In addition, IFN-gamma production, if present, falls off with time. Thus the cells in these cultures take on an increasingly Th2-like phenotype. It appears that the effects of low levels of IL-4 in suppressing IL-2 production by day 4 effectors appear to be transient whereas the higher levels appear to drive the development along a distinct pathway which is irreversible. These studies support the concept that different subsets of helper cells, which correspond roughly to Th1 and Th2 subsets, can develop rapidly in short term culture with respectively low vs high levels of IL-4. They support the concept that such distinct phenotypes arise from alternate pathways of differentiation that can be expected to reflect pathways available for helper T cell differentiation in the animal.     

Suppression of early IL-4 production underlies the failure of CD4 T cells activated by TLR-stimulated dendritic cells to differentiate into Th2 cells

Dendritic cells (DCs) activated through TLRs provide a potent negative signal for Th2 cell development that is independent of positive signals for Th1 cell development such as IL-12 and IFN-gamma. In this study we demonstrate that the ability of TLR-activated DCs to suppress Th2 cell development is Ag dose-independent and unique to DCs that have been activated through TLRs vs by cytokines. We show that TLR-activated DCs inhibit early IL-4 production by CD4 T cells and thus inhibit their ability to subsequently increase GATA-3 expression and commit to the Th2 lineage. This occurs independently of expression of the GATA-3 antagonist T-bet. Although CD4 T cells activated by TLR-activated DCs make IL-2, they are not capable of phosphorylating STAT5 in response to this cytokine. This inhibition of responsiveness to IL-2 appears to underlie the failure to make early IL-4. Our findings suggest that DCs provide instructional signals for T cell differentiation before cytokine-mediated Th cell selection and outgrowth.     

The action of interleukin-4 on antigen-specific IgG1 and IgE production by interaction of in vivo primed B cells and carrier-specific cloned Th2 cells

The production of anti-trinitrophenyl (TNP) antibodies of different isotypes from in vivo primed B cells was studied using the plaque-forming cell method. It was shown that these B cells secrete anti-trinitrophenyl antibodies of different isotypes only in the presence of Th2 cells specific for keyhole limpet hemocyanin (KLH) and the hapten-carrier conjugate TNP-KLH. Lipopolysaccharide-stimulated primed B cells without cells from the Th2 clone did not produce anti-TNP-specific IgG1 or IgE antibodies even in the presence of the hapten-carrier antigen TNP-KLH. Supernatants from these Th2 clones cultured with antigen-presenting cells and the complete antigen were unable to activate primed B cells for antibody secretion. Cognate interaction between primed B cells and carrier-specific Th2 cells is a prerequisite for hapten-specific IgG1 or IgE production. Anti-IL-4 antibody inhibited secretion of anti-hapten IgE antibody. Therefore, for production of anti-hapten antibody of the IgE isotype IL-4 is also necessary.     

Aluminium hydroxide adjuvant initiates strong antigen-specific Th2 responses in the absence of IL-4- or IL-13-mediated signaling

Previous studies demonstrate that aluminium hydroxide adjuvant (alum) produces increased Th1 responses in IL-4-deficient mice compared with wild-type animals, although the continued production of IL-5 by spleen cells from these mice also indicates that Th2 responses are induced. In the present study, we demonstrate that alum can induce Th2-associated IL-4 and IL-5 production in the absence of IL-4 signaling in mice deficient in either IL-4Ralpha or Stat6. The Th2 responses observed could not be due to IL-13 as IL-13 responses are also impaired in IL-4Ralpha- and Stat6-deficient mice. We also detected higher levels of IL-4 in IL-4Ralpha gene-deficient, though not Stat6-deficient, mice compared with their wild-type counterparts. The increased levels of IL-4 could be explained by the IL-4R being unavailable to neutralize this cytokine in IL-4Ralpha-deficient mice. While levels of IL-5 production in IL-4Ralpha- or Stat6-deficient mice were similar to IL-4-deficient and wild-type mice, other type 2-associated responses, which are largely or wholly IL-4 dependent, such as the production of IgG1 or IgE Abs, were either reduced or absent. We conclude that alum adjuvants can induce IL-4 production and Th2 responses independently of IL-4 or IL-13, negating the requirement for an early source of IL-4 in the Th2 response induced by this adjuvant.     

IL-4 is a mediator of IL-12p70 induction by human Th2 cells: reversal of polarized Th2 phenotype by dendritic cells

IL-12 is a key inducer of Th1-associated inflammatory responses, protective against intracellular infections and cancer, but also involved in autoimmune tissue destruction. We report that human Th2 cells interacting with monocyte-derived dendritic cells (DC) effectively induce bioactive IL-12p70 and revert to Th0/Th1 phenotype. In contrast, the interaction with B cells preserves polarized Th2 phenotype. The induction of IL-12p70 in Th2 cell-DC cocultures is prevented by IL-4-neutralizing mAb, indicating that IL-4 acts as a Th2 cell-specific cofactor of IL-12p70 induction. Like IFN-gamma, IL-4 strongly enhances the production of bioactive IL-12p70 heterodimer in CD40 ligand-stimulated DC and macrophages and synergizes with IFN-gamma at low concentrations of both cytokines. However, in contrast to IFN-gamma, IL-4 inhibits the CD40 ligand-induced production of inactive IL-12p40 and the production of either form of IL-12 induced by LPS, which may explain the view of IL-4 as an IL-12 inhibitor. The presently described ability of IL-4 to act as a cofactor of Th cell-mediated IL-12p70 induction may allow Th2 cells to support cell-mediated immunity in chronic inflammatory states, including cancer, autoimmunity, and atopic dermatitis.     

Cutting edge: IL-4 receptor expression by non-bone marrow-derived cells is required to expel gastrointestinal nematode parasites.

Expulsion of two gastrointestinal nematode parasites, Nippostrongylus brasiliensis and Trichinella spiralis, is similar in that both require IL-4Ralpha expression, but different in that T cells and mast cells are required for IL-4-induced expulsion of T. spiralis but not N. brasiliensis. To examine the role of IL-4Ralpha signaling in immunity to these parasites, we studied worm expulsion in chimeric mice that selectively expressed IL-4Ralpha on bone marrow-derived or non-bone marrow-derived cells. N. brasiliensis was expelled by mice that expressed IL-4Ralpha only on non-bone marrow-derived cells, but not by mice that expressed IL-4Ralpha only on bone marrow-derived cells. Although T. spiralis expulsion required IL-4Ralpha expression by both bone marrow- and non-bone marrow-derived cells, IL-4 stimulation eliminated the requirement for IL-4Ralpha expression by bone marrow-derived cells. Thus, direct IL-4Ralpha signaling of nonimmune gastrointestinal cells may be generally required to induce worm expulsion, even when mast cell and T cell responses are also required.