Sterile protection of monkeys against malaria after administration of interleukin-12.

An estimated 300-500 million new infections and 1.5-2.7 million deaths attributed to malaria occur annually in the developing world, and every year tens of millions of travelers from countries where malaria is not transmitted visit countries with malaria. Because the parasites that cause malaria have developed resistance to many antimalarial drugs, new methods for prevention are required. Intraperitoneal injection into mice of one dose of 150 ng (approximately 7.5 micrograms per kg body weight) recombinant mouse interleukin-12 (rmIL-12) 2 days before challenge with Plasmodium yoelii sporozoites protects 100% of mice against malaria. We report that one subcutaneous injection of 10 micrograms/kg recombinant human IL-12 (rhIL-12) 2 days before challenge with P. cynomolgi sporozoites protected seven of seven rhesus monkeys. Protection was associated with marked increases in plasma levels of interferon-gamma (IFN-gamma), and relative increases of lymphoid cell messenger RNA coding for IFN-gamma and several other cytokines. We speculate that rIL-12 protects monkeys through IFN-gamma-dependent elimination of P. cynomolgi-infected hepatocytes. This first report of rIL-12-induced protection of primates against an infectious agent supports assessment of rhIL-12 for immunoprophylaxis of human malaria.

Distinct roles for IL-13 and IL-4 via IL-13 receptor alpha1 and the type II IL-4 receptor in asthma pathogenesis.

IL-13 and IL-4 are central T helper 2 (Th2) cytokines in the immune system and potent activators of inflammatory responses and fibrosis during Th2 inflammation. Recent studies using Il13ra1(-/-) mice have demonstrated a critical role for IL-13 receptor (IL-13R) alpha1 in allergen-induced airway responses. However, these observations require further attention especially because IL-4 can induce similar lung pathology to IL-13, independent of IL-13, and is still present in the allergic lung. Thus, we hypothesized that IL-13Ralpha1 regulates IL-4-induced responses in the lung. To dissect the role of IL-13Ralpha1 and the type I and II IL-4Rs in experimental asthma, we examined lung pathology induced by allergen, IL-4, and IL-13 challenge in Il13ra1(-/-) mice. We report that IL-13Ralpha1 is essential for baseline IgE production, but Th2 and IgE responses to T cell-dependent antigens are IL-13Ralpha1-independent. Furthermore, we demonstrate that increased airway resistance, mucus, TGF-beta, and eotaxin(s) production, but not cellular infiltration, are critically dependent on IL-13Ralpha1. Surprisingly, our results identify a CCR3- and IL-13Ralpha1-independent pathway for lung eosinophilia. Global expression profiling of lungs from mice stimulated with allergen or IL-4 demonstrated that marker genes of alternatively activated macrophages are differentially regulated by the type I and type II IL-4R. Taken together, our data provide a comprehensive mechanistic analysis of the critical role by which IL-13Ralpha1 mediates allergic lung pathology and highlight unforeseen roles for the type II IL-4R.

Differential regulation of IgG1 and IgE synthesis by interleukin 4.

IL-4/B cell stimulatory factor-1 is a T cell-derived lymphokine that has been shown to enhance IgG1 and IgE and to suppress IgG3 and IgG2b secretion by B cells stimulated with bacterial LPS. We show here that the stimulation of IgG1 and IgE secretion in response to rIL-4 is differentially regulated. The dose-response curve for IgG1 production is bimodal with peaks at 100 and 10,000 U/ml. IgE production is modest at 100 U/ml and exhibits a progressive enhancement as the IL-4 concentration is increased to 10,000 U/ml, reaching approximately 1 microgram of IgE from an initial cell number of 2 X 10(4). Both of these effects are reversed by monoclonal anti-IL-4 antibody. Neither the enhancing nor suppressing effects of IL-4 can be explained by changes in viable cell yields or [3H]thymidine incorporation. The production of both IgG1 and IgE is controlled by IL-4 in a two-phase manner. During the initial 2 d of culture with LPS, IL-4 action for both IgG1 and IgE production is relatively concentration independent at doses greater than 600 U/ml. This 2-d treatment leads to maximal IgG1 production at day 6 with no further addition of IL-4. Addition of IL-4 during the final 4 d of culture has no effect at concentrations under 100 U/ml. At higher concentrations, IL-4 is strikingly suppressive for IgG1 production. By contrast, little IgE is produced unless IL-4 is present after 2 d of culture and the response is directly dependent on the concentration of IL-4 during this second phase of culture with maximal responses observed at 10,000 U/ml. These differences in IL-4 requirements for IgG1 and IgE production, respectively, may have an important role in the regulation of the synthesis of these isotypes in responses to microbial antigens.

Evidence for the involvement of interleukin 10 in the differential deactivation of murine peritoneal macrophages by prostaglandin E2.

Among other effects, prostaglandins (PG) of the E series are known to inhibit several acute and chronic inflammatory conditions in vivo and proinflammatory cytokine production by activated macrophages in culture. The research presented here demonstrates that the inhibitory effect of PGE2 on tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) production by lipopolysaccharide (LPS)-stimulated murine peritoneal macrophages involves IL-10. In a dose-dependent manner, PGE2 inhibits LPS-induced release of TNF-alpha and IL-6, but not of lactate or nitric oxide. The decrease in the level of these cytokines is inversely proportional to the increase in immunoreactive IL-10. This differential inhibitory effect of PGE2 is mimicked by agents that elevate intracellular levels of cAMP, but not cGMP. Neutralizing anti IL-10 antibody but not neutralizing antibodies against other macrophage secretory products (IL-6, leukemia inhibitory factor, and transforming growth factor beta [TGF-beta]), significantly reverse the potent inhibitory effect of PGE2. In vivo, the administration of PGE2 before LPS challenge significantly reduces circulating TNF-alpha and IL-6 levels. Anti-IL-10 antibody substantially enhanced the LPS-induced TNF-alpha and IL-6 levels in mice that received either LPS alone or LPS plus PGE2. These results suggest that the anti-inflammatory effect of PGE2 on mononuclear phagocytes is mediated in part by an autocrine feedback mechanism involving IL-10.

Abnormal ratio of membrane immunoglobulin classes in mice with an X-linked B-lymphocyte defect.

CBA/N mice have an X-linked genetic defect in B-lymphocyte function manifested by inability to make antibody responses to T-independent antigens. Plasma membrane immunoglobulin (Ig) on spleen, lymph node, and Peyer's patch cells was analyzed by lactoperoxidase-catalyzed iodination, NP-40 extraction, specific immunoprecipitation, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These studies indicated that the X-linked immune defect was associated, in all three cell types, with a decrease in the ratio of cell membrane IgD analog to cell membrane IgM. This suggests either that IgD analog may be important in initiation of T-independent antibody responses or that CBA/N mice lack a subpopulation of B cells specialized to respond to T-independent antigens, and that these cells are relatively rich in plasma membrane IgD analog.

Cross-linking of membrane immunoglobulin D, in the absence of T cell help, kills mature B cells in vivo.

In vivo experiments were performed to determine whether the cross-linking of membrane immunoglobulin (mIg) D on mature B cells, in the absence of T cell help, leads to B cell death. Mice were injected with either a monoclonal antibody (mAb) that cross-links mIgD effectively or a mAb that binds to mIgD avidly but cross-links it to a limited extent, and effects on B cell number and B cell Ia, mIgM, and mIgD expression were observed. In most experiments, mice were pretreated with anti-interleukin 7 mAb to prevent the generation of new bone marrow B cells, and with anti-CD4 mAb to prevent the generation of T cell help. In some experiments, mice also received anti-Fc gamma RII mAb to prevent cross-linking of mIgD with Fc gamma RII, and cobra venom factor to prevent possible mIg-complement receptor interactions and complement-mediated killing of B cells. The results of these studies demonstrate that (a) even limited cross-linking of mIgD on mature B cells can lead to B cell death; (b) increased cross-linking of mIgD leads to increased B cell death; (c) the loss of B cells is first detected 2 d after anti-IgD mAb injection and increases during the subsequent 3 d; (d) sustained modulation of mIgD may be necessary to cause B cell death; (e) mIgMdull but not mIgMbright B cells are lost in mice injected with anti-IgD mAbs; and (f) T cell help prevents or minimizes B cell death.

Crosslinkage of B lymphocyte surface immunoglobulin by anti-Ig or antigen induces prolonged oscillation of intracellular ionized calcium.

Our results indicate that B lymphocytes stimulated with anti-Ig or antigen exhibit repetitive [Ca2+]i transients which persist for hours. The magnitude of these transients favors an important and ongoing role for [Ca2+]i elevation in antigen driven B cell activation. Repetitive Ca2+ transients may prove to be a prevalent mechanism of Ca2+ signaling. In preliminary experiments (with L. E. Samelson and R. D. Klausner), we have observed Ca2+ transients in cloned T cells stimulated with antigen. Woods et al. have described repetitive free Ca2+ transients in hepatocytes stimulated with extracellular ligands promoting glycogenolysis, and suggest that the intervals of base-line [Ca2+]i levels explain the absence of mitochondrial overload in chronically stimulated cells. These considerations apply equally to B lymphocytes and recommend caution in delineating the range of Ca2+-mediated functions by prolonged coculture of cells with Ca2+ ionophores. Our experiments were done in a simple recording chamber with one cell type. No cell interactions were observed. Given the variety of indicator dyes now available, the technical approach we present, augmented by a more sophisticated recording chamber, is a potentially powerful tool for examining the intrinsic, and T- or accessory cell-dependent, physiology of B cell differentiation.

Acquisition of cell surface IgD after in vitro culture of neoplastic B cells from the murine tumor BCL1.

Murine BCL1 tumor cells bear large amounts of surface IgM and trace amounts of surface IgD. In the present studies we have shown that cultivation of these cells, in the absence of lipopolysaccharide, results in the acquisition of IgD by virtually all the cells. These results suggest that BCL1 cells can differentiate in vitro into more mature B cells and offer an attractive model for analyzing the factors controlling appearance of IgD on a monoclonal cell line.

Generation of interleukin 4 (IL-4)-producing cells in vivo and in vitro: IL-2 and IL-4 are required for in vitro generation of IL-4-producing cells.

T cell populations derived from naive mice produce very small amounts of interleukin 4 (IL-4) in response to stimulation on anti-CD3-coated dishes. IL-4 production by such cells is mainly found among large- and intermediate-sized T cells and is dependent upon IL-2. Injection of anti-IgD into mice, a stimulus that leads to striking increases in serum levels of IgG1 and IgE, causes a striking increase in the IL-4-producing capacity of T cells. This increase is first observed 4 d after injection of anti-IgD. IL-4 production by T cells from anti-IgD-injected donors is mainly found among large- and intermediate-sized T cells. Small, dense T cells are poor producers of IL-4. The capacity of T cells from anti-IgD-injected donors to produce IL-4 is enhanced by addition of IL-2 and is largely, but not completely, inhibited by neutralization of in situ produced IL-2. These results indicate that the control of IL-4 production in T cells from naive and anti-IgD-injected donors is similar. However, it is possible that a portion of the IL-4-producing activity of T cells from activated donors is IL-2 independent. Although small T cells from naive donors have a very limited capacity to produce IL-4 in response to stimulation with anti-CD3, even in the presence of added IL-2, they can give rise to IL-4-producing cells upon in vitro culture on plates coated with anti-CD3 if both IL-2 and IL-4 are added. This leads to the appearance of IL-4-producing cells within 2 d. When analyzed after 5 d of culture by harvesting and re-exposure to anti-CD3-coated culture wells and IL-2, these cells have increased their IL-4-producing capacity by approximately 100-fold. The development of IL-4-producing cells in response to anti-CD3, IL-2, and IL-4 is not inhibited by interferon gamma (IFN-gamma), nor does IFN-gamma diminish IL-4 production by these cells upon challenge with anti-CD3 plus IL-2.

Cytokine-mediated regulation of chronic intestinal helminth infection.

Most inbred strains of mouse infected with the intestinal nematode Trichuris muris are resistant to infection expelling the parasite before adult worms establish. However, a few susceptible strains exist that are incapable of worm expulsion and harbor chronic infections of mature adult worms. Analyses of in vitro cytokine production by cells from the draining lymph node (mesenteric lymph node) have indicated that expulsion phenotype is tightly correlated with the selective expansion of helper T cells (Th) of the Th1 or Th2 cell subset within the mesenteric lymph node, resulting in susceptibility and resistance to T. muris, respectively. We have now confirmed and extended our in vitro observations in a series of experiments involving the in vivo manipulation of host cytokine levels. Depletion of interferon (IFN)-gamma in normally susceptible mice resulted in expulsion of the parasite, representing the first evidence for a role for IFN-gamma in the establishment of chronic helminth infection. Blocking interleukin (IL)-4 function in normally resistant animals prevented the generation of a protective immune response allowing adult stages of the parasite to develop. Conversely the administration of IL-4 to a normally susceptible host facilitated expulsion and indeed enabled established adult worms to be expelled when administered late in infection. In all cases assessment of a variety of in vivo parameters indicative of a Th1- or Th2-type response (parasite-specific immunoglobulin (Ig) G2a and the parasite-specific IgG1, total IgE levels and intestinal mastocytosis, respectively) demonstrated that the in vivo modulation of a Th1- or Th2-specific cytokine allowed the reciprocal Th cell subset to expand and become dominant with dramatic consequences for worm expulsion.

Persistent calcium elevation correlates with the induction of surface immunoglobulin-mediated B cell DNA synthesis.

Surface immunoglobulin (sIg)-mediated stimulation of B lymphocytes induces a tyrosine kinase-dependent sequence of events leading to rapid and large elevations in intracellular ionized calcium ([Ca2+]i). These early biochemical events do not necessarily lead to proliferation of B cells, however, and conversely, the absence of or inhibition of these events does not necessarily prevent cellular proliferation. We now show by digital image analysis of single B cells that conditions which lead to B cell proliferation are associated with low-level but persistent sustained or cyclic elevations in [Ca2+]i. In marked contrast, early and nonsustained elevations in [Ca2+]i are induced in B cells by stimuli that lead to G1 transition but fail to progress to DNA synthesis. Thus, when B cells were stimulated with mitogenic and nonmitogenic anti-IgD antibodies, both of which induce entry of cells into G1 and early calcium transients of comparable magnitude, persistent low-level calcium elevations were only detected in cells stimulated with the mitogenic antibody. Furthermore, persistent calcium elevations were also seen when B cells were stimulated with a multivalent dextran-anti-Ig conjugate which induced very high levels of B cell proliferation in the absence of detectable phosphatidylinositol 4,5-biphosphate hydrolysis or elevations in [Ca2+]i as detected by flow cytometry. Finally, B cells from X-linked B cell-defective mice, which do not proliferate in response to anti-Ig antibody, show marked and early increases in [Ca2+]i, but do not show persistent calcium elevations. These data suggest that the rapid and large increases of [Ca2+]i seen in lymphocytes within seconds after antigen receptor ligation may be associated with entry in G1, whereas low-level but persistent elevations may be the hallmark of a cell destined to synthesize DNA.

bcl-x exhibits regulated expression during B cell development and activation and modulates lymphocyte survival in transgenic mice.

We have assessed during B cell development, the regulation and function of bcl-x, a member of the bcl-2 family of apoptosis regulatory genes. Here we show that Bcl-xL, a product of bcl-x, is expressed in pre-B cells but downregulated at the immature and mature stages of B cell development. Bcl-xL but not Bcl-2 is rapidly induced in peripheral B cells upon surface immunoglobulin M (IgM) cross-linking, CD40 signaling, or LPS stimulation. Transgenic mice that overexpressed Bcl-xL within the B cell lineage exhibited marked accumulation of peripheral B cells in lymphoid organs and enhanced survival of developing and mature B cells. B cell survival was further increased by simultaneous expression of bcl-xL and bcl-2 transgenes. These studies demonstrate that Bcl-2 and Bcl-xL are regulated differentially during B cell development and activation of mature B cells. Induction of Bcl-xL after signaling through surface IgM and CD40 appears to provide mature B cells with an additional protective mechanism against apoptotic signals associated with antigen-induced activation and proliferation.

Regulation by interferon alpha of immunoglobulin isotype selection and lymphokine production in mice.

Antigens and infectious agents that stimulate interferon alpha(IFN-alpha) production in mice induce antibody responses that are predominantly of the immunoglobulin (Ig)G2a isotype and contain little or no IgE. This suggested the possibility that IFN-alpha might have a role in directing Ig isotype selection. Consistent with this possibility, we have found that injection of mice with recombinant mouse IFN-alpha suppresses IgE secretion, enhances IgG2a secretion, and has no independent effect on IgG1 secretion in mice stimulated with a foreign anti-IgD antibody. Injection of mice with polyinosinic acid.polycytidylic acid (poly I.C), an inducer of macrophage IFN-alpha production, also suppresses the anti-IgD antibody-induced IgE response and stimulates the IgG2a response; these effects are blocked by a sheep antibody that neutralizes mouse IFN-alpha/beta. Both recombinant IFN-alpha and poly I.C have maximum IgE suppressive and IgG2a stimulatory effects when injected early in the anti-IgD antibody-induced immune response. Addition of IFN-alpha to mouse B cells cultured with lipopolysaccharide (LPS) + interleukin 4 (IL-4) suppresses both IgG1 and IgE production, but much less potently than IFN-gamma. IFN-alpha suppresses anti-IgD antibody-induced increases in the level of splenic IL-4 mRNA, but enhances the anti-IgD antibody-induced increase in the splenic level of IFN-gamma mRNA. These results are consistent with the effect of IFN-alpha on Ig isotype expression in mice, as IL-4 stimulates IgE and suppresses IgG2a secretion while IFN-gamma exerts opposite effects. These observations suggest that antigen presenting cells, by secreting IFN-alpha early in the course of an immune response, can influence the nature of that response both through direct effects on B cells and by influencing the differentiation of T cells.

Interleukin 12 inhibits antigen-induced airway hyperresponsiveness, inflammation, and Th2 cytokine expression in mice.

Allergic asthma is characterized by airway hyperresponsiveness and pulmonary eosinophilia, and may be mediated by T helper (Th) lymphocytes expressing a Th2 cytokine pattern. Interleukin (IL) 12 suppresses the expression of Th2 cytokines and their associated responses, including eosinophilia, serum immunoglobulin E, and mucosal mastocytosis. We have previously shown in a murine model that antigen-induced increases in airway hyperresponsiveness and pulmonary eosinophilia are CD4+ T cell dependent. We used this model to determine the ability of IL-12 to prevent antigen-induced increases in airway hyperresponsiveness, bronchoalveolar lavage (BAL) eosinophils, and lung Th2 cytokine expression. Sensitized A/J mice developed airway hyperresponsiveness and increased numbers of BAL eosinophils and other inflammatory cells after single or repeated intratracheal challenges with sheep red blood cell antigen. Pulmonary mRNA and protein levels of the Th2 cytokines IL-4 and IL-5 were increased after antigen challenge. Administration of IL-12 (1 microgram/d x 5 d) at the time of a single antigen challenge abolished the airway hyperresponsiveness and pulmonary eosinophilia and promoted an increase in interferon (IFN) gamma and decreases in IL-4 and IL-5 expression. The effects of IL-12 were partially dependent on IFN-gamma, because concurrent treatment with IL-12 and anti-IFN-gamma monoclonal antibody partially reversed the inhibition of airway hyperresponsiveness and eosinophilia by IL-12. Treatment of mice with IL-12 at the time of a second antigen challenge also prevented airway hyperresponsiveness and significantly reduced numbers of BAL inflammatory cells, reflecting the ability of IL-12 to inhibit responses associated with ongoing antigen-induced pulmonary inflammation. These data show that antigen-induced airway hyperresponsiveness and inflammation can be blocked by IL-12, which suppresses Th2 cytokine expression. Local administration of IL-12 may provide a novel immunotherapy for the treatment of pulmonary allergic disorders such as atopic asthma.

Induction of IgG3 secretion by interferon gamma: a model for T cell-independent class switching in response to T cell-independent type 2 antigens.

T cell-independent type 2 (TI-2), in contrast to T-dependent, antigens stimulate the production of murine IgG3. To investigate a possible role for cytokines in mediating the induction of this IgG subclass, we established an in vitro polyclonal model system for studying TI-2 antigen-mediated B cell activation by using dextran-conjugated anti-IgD antibody (alpha delta-dex). We demonstrate that interferon gamma (IFN-gamma) stimulates, and interleukin 4 inhibits, the expression of IgG3 by alpha delta-dexactivated cells. The production of IFN-gamma by non-T cells in response to bacterial products, possibly capsular polysaccharides, may provide an explanation underlying the ability of TI antigens, which are unable to directly stimulate T cell-derived cytokines to induce Ig isotype switching.

Role of the thymus in directing the development of a subset of B lymphocytes.

In an effort to evaluate the role of the thymus in influencing the development of Lyb-5- B lymphocytes, mice expressing both the xid and nu gene defects were studied. Mice expressing either of these defects respond to both trinitrophenylated Brucellus abortus and lipopolysaccharide; whereas mice with the combined defect show markedly suppressed responses. The other abnormalities included: (a) greater than 80 percent diminution of serum Ig levels; (b) significant increase in the number of sIgM+ sIgD- B lymphocytes; (c) reduced expression of IgD on sIgD+ cells; and (d) a strikingly abnormal histology of their lymphoid tissue. Because nu/nu mice that do not express the xid defect appear relatively normal, it would suggest that the development of Lyb-5- B lymphocytes require a thymic influence for normal maturation, whereas, Lyb-5+ B lymphocytes are relatively independent of such influences.

Infection with Nippostrongylus brasiliensis or injection of anti-IgD antibodies markedly enhances Fc-receptor-mediated interleukin 4 production by non-B, non-T cells.

Non-B, non-T cells from spleen and bone marrow of naive mice produce IL-4 upon stimulation by plate-bound IgE or IgG2a in the presence of IL-3. Infection of mice with Nippostrongylus brasiliensis (Nb) or injection of anti-IgD antibodies, treatments known to cause striking polyclonal IgE responses, increase the number of splenic non-B, non-T cells and cause 10-30-fold increase in IL-4 production by a standard number of these cells. In Nb-infected mice, IL-4 producing non-B, non-T cells can be found in the lungs, a site through which Nb larvae migrate. Non-B, non-T cells from anti-IgD-injected mice produce IL-4 in response to anti-IgE antibodies, indicating that these cells have been sensitized in vivo with IgE and that crosslinkage of such IgE can lead to stimulation of lymphokine production. Similarly, non-B, non-T cells from Nb-infected mice produce IL-4 upon stimulation with Nb-antigen, indicating that antigen can also crosslink receptors on in vivo sensitized non-B, non-T cells and stimulate lymphokine production. The striking increases in the IL-4-producing capacity of the splenic non-B, non-T cell population in anti-IgD-injected and Nb-infected mice and the in vivo sensitization of these cells strongly suggests that they may have an important role in lymphokine production in helminthic infections and other situations marked by striking elevations of serum IgE levels.

Oral but not parenteral interleukin (IL)-12 redirects T helper 2 (Th2)-type responses to an oral vaccine without altering mucosal IgA responses.

Our past studies have shown that the mucosal adjuvant cholera toxin (CT) induces T helper type 2 (Th2) responses with systemic IgG1, IgE and mucosal secretory IgA (S-IgA) antibodies (Abs). In this study, recombinant murine IL-12 (rmIL-12) was given either parenterally or orally to mice orally immunized with tetanus toxoid (TT) and CT to determine whether this cytokine could redirect the CT-induced Th2-type responses and what effect this shift would have on S-IgA Ab responses. Intraperitoneal administration of rmIL-12 shifted TT-specific responses toward Th1-type and resulted in CD4+ T cells producing IFN-gamma and IL-2 with markedly reduced levels of Th2-type cytokines. This cytokine profile was accompanied by increased delayed-type hypersensitivity (DTH) and shifts in serum IgG1 to IgG2a and IgG3 anti-TT Ab responses. Further, serum IgE and S-IgA Ab responses were markedly reduced by parenteral IL-12. When IL-12 complexed to liposomes was given orally both shifts to IgG2a and IgG3 and low IgE Abs again occurred concomitant with enhanced serum IFN-gamma and DTH responses. Interestingly, oral rmIL-12 did not result in significant levels of serum IL-12 nor altered S-IgA Ab responses and resulted in higher levels of some Th2-type cytokines both in vitro and in vivo when compared with parenteral IL-12. Our results show that the shifts in systemic immune responses with intact S-IgA Abs which occur after oral delivery of IL-12-liposomes are due to cytokine effects in the Peyer's patches and suggest new strategies for the targeted manipulation of Th1- and Th2-type responses to mucosal vaccines.

CTLA-4 ligands are required to induce an in vivo interleukin 4 response to a gastrointestinal nematode parasite.

The costimulatory signal provided to T cells through CTLA-4-ligand interactions is required for T cell activation resulting in increased interleukin 2 (IL-2) production in vitro, but its role in the production of IL-4 and other cytokines is unclear and few in vivo studies have been performed to confirm results of in vitro experiments. We have examined the in vivo effects of blocking CTLA-4 ligands on the T helper cell 2 (Th2)-associated mucosal immune response that follows oral infection of mice with the nematode parasite, Heligmosomoides polygyrus. CTLA-4Ig administration inhibited H. polygyrus-induced increases in mesenteric lymph node (MLN) B cell major histocompatibility complex class II expression and size and T cell-derived IL-4 gene expression. In addition, CTLA-4 immunoglobulin (Ig) partially blocked increased IL-3, IL-5, and IL-9 cytokine gene expression in Peyer's patch (PP) and MLN 8 d after primary inoculation of mice with the parasite. Increases in the number of IL-4- but not IL-5-secreting cells were also inhibited by CTLA-4Ig. H. polygyrus-induced elevations in serum IgE levels but not blood eosinophils, were markedly inhibited by CTLA-4Ig. These results suggest that stimulation of CD28 and/or CTLA-4 is required for T cell priming leading to IL-4 cytokine production, B cell activation, and IgE secretion during a Th2-like, mucosal immune response to a nematode parasite.

Inhibition of murine B and T lymphopoiesis in vivo by an anti-interleukin 7 monoclonal antibody.

The effects of interleukin 7 (IL-7) on the growth and differentiation of murine B cell progenitors has been well characterized using in vitro culture methods. We have investigated the role of IL-7 in vivo using a monoclonal antibody that neutralizes IL-7. We find that treatment of mice with this antibody completely inhibits the development of B cell progenitors from the pro-B cell stage forward. We also provide evidence that all peripheral B cells, including those of the B-1 and conventional lineages, are derived from IL-7-dependent precursors. The results are consistent with the rapid turnover of B cell progenitors in the marrow, but a slow turnover of mature B cells in the periphery. In addition to effects on B cell development, anti-IL-7 treatment substantially reduced thymus cellularity, affecting all major thymic subpopulations.