Differential effect of vasoactive intestinal peptide, somatostatin, and substance P on human IgE and IgG subclass production

Sensory neurons regulate stimulus-dependent humoral immunity

Sensory neurons sense pathogenic infiltration, serving to inform immune coordination of host defense. However, sensory neuron-immune interactions have been predominantly shown to drive innate immune responses. Humoral memory, whether protective or destructive, is acquired early in life - as demonstrated by both early exposure to streptococci and allergic disease onset. Our study further defines the role of sensory neuron influence on humoral immunity in the lung. Using a murine model of Streptococcus pneumonia pre-exposure and infection and a model of allergic asthma, we show that sensory neurons are required for B-cell and plasma cell recruitment and antibody production. In response to S. pneumoniae , sensory neuron depletion resulted in a larger bacterial burden, reduced B-cell populations, IgG release and neutrophil stimulation. Conversely, sensory neuron depletion reduced B-cell populations, IgE and asthmatic characteristics during allergen-induced airway inflammation. The sensory neuron neuropeptide released within each model differed. With bacterial infection, vasoactive intestinal polypeptide (VIP) was preferentially released, whereas substance P was released in response to asthma. Administration of VIP into sensory neuron-depleted mice suppressed bacterial burden and increased IgG levels, while VIP1R deficiency increased susceptibility to bacterial infection. Sensory neuron-depleted mice treated with substance P increased IgE and asthma, while substance P genetic ablation resulted in blunted IgE, similar to sensory neuron-depleted asthmatic mice. These data demonstrate that the immunogen differentially stimulates sensory neurons to release specific neuropeptides which specifically target B-cells. Targeting sensory neurons may provide an alternate treatment pathway for diseases involved with insufficient and/or aggravated humoral immunity.

The significance of vasoactive intestinal peptide in immunomodulation

First identified by Said and Mutt some 30 years ago, the vasoactive intestinal peptide (VIP) was originally isolated as a vasodilator peptide. Subsequently, its biochemistry was elucidated, and within the 1st decade, their signature features as a neuropeptide became consolidated. It did not take long for these insights to permeate the field of immunology, out of which surprising new attributes for VIP were found in the last years. VIP is rapidly transforming into something more than a mere hormone. In evolving scientifically from a hormone to a novel agent for modifying immune function and possibly a cytokine-like molecule, VIP research has engaged many physiologists, molecular biologists, biochemists, endocrinologists, and pharmacologists and it is a paradigm to explore mutual interactions between neural and neuroendocrine links in health and disease. The aim of this review is firstly to update our knowledge of the cellular and molecular events relevant to VIP function on the immune system and secondly to gather together recent data that support its role as a type 2 cytokine. Recognition of the central functions VIP plays in cellular processes is focusing our attention on this "very important peptide" as exciting new candidates for therapeutic intervention and drug development.

Neurotrophins and neurotrophin receptors in allergic asthma

The neurotrophins nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3 (NT-3) and NT-4 play a pivotal role in the development of the nervous system. Despite their well-known effects on neurons, elevated neurotrophin concentrations have been observed under pathological conditions in sera of patients with inflammatory disorders. Patients with asthma feature both airway inflammation and an abnormal airway reactivity to many unspecific stimuli, referred to as airway hyperresponsiveness, which is, at least partly, neuronally controlled. Interestingly, these patients show increased levels of neurotrophins in the blood as well as locally in the lung. It has been demonstrated that neurotrophin release from immune cells is triggered by allergen contact. The presence of neurotrophins and the neurotrophin receptors p75 (p75NTR), tyrosine kinase A (TrkA), TrkB and TrkC have been described in several immune cells. There is strong evidence for an involvement of neurotrophins in regulation of hematopoiesis and, in addition, in modulation of immune cell function in mature cells circulating in blood or resting in lymphatic organs and peripheral tissues. The aim of this review is to demonstrate possible roles of neurotrophins during an allergic reaction in consideration of the temporospatial compartimentalization.

Neuropeptides modulate a murine monocyte/macrophage cell line capacity for phagocytosis and killing of Leishmania major parasites

Host-parasite interactions and their outcome constitute a critical and challenging step in disease establishment in cutaneous leishmaniasis. In the present in vitro study we investigated the possible modulating effects of both sensory and autonomic neuropeptides that normally exist in human and mouse skin, on the uptake and leishmanicidal capacity of macrophages on Leishmania (L.) major parasites, using a monocyte/macrophage murine cell line (Raw 264.7). The sensory neuropeptides somatostatin (SOM), calcitonin gene-related peptide (CGRP) and substance P (SP) suppressed the macrophage capacity for phagocytosing L. major promastigotes at different concentrations, 10(-10) - 10(-5) M, however, the suppressive effect of SP does not reach a significant level. CGRP and SP enhanced the leishmanicidal capacity of macrophages at 10(-7) M, and 10(-5) M, respectively, whereas SOM was without effect. The autonomic neuropeptides vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY) both suppressed the phagocytic and leishmanicidal capacities of macrophages at various concentrations, 10(-10) - 10(-5) M. The findings indicate that neuropeptides have modulating effects on macrophage-L. major interactions. These effects might be exerted by a direct action on macrophages or indirectly through induction of other mediators.

Differential modulation of human immunoglobulin isotype production by the neuropeptides substance P, NKA and NKB

The modifying effects of tachykinins substance P, neurokinin A and neurokinin B on immunoglobulin production were analyzed in an in vitro culture system. Purified human T- and B-cells were stimulated with TGFbeta2 and IL-5 to induce preferential IgA production. Neuropeptides had the following effects. (1) The levels of IgA and IgG4 production were enhanced by IL-5 and TGFbeta2; IgA levels remained constant or were slightly augmented by neuropeptides, whereas IgG4 was further augmented. (2) IL-5 and TGFbeta2 did not alter IgG3 production, but neuropeptides stimulated secretion of this subclass. (3) IgG1 and IgM production were inhibited by IL-5 and TGFbeta2. This effect was prevented by neuropeptides. (4) Other isotypes including IgG2 and IgE remained unaffected. Except for IgM, these effects were blocked by specific receptor antagonists indicating specificity. The tachykinin receptor NK-1 mRNA was detected in B- and T-cells, whereas NK-3 mRNA was only present in T- and B-cell coculture following activation. Furthermore, neuropeptide effects depended on cytokine co-stimulation and the presence of T-cells. These results suggest that neuropeptides are potent modifiers of preferential IgA synthesis.

Somatostatin and octreotide modulate the function of Kupffer cells in liver cirrhosis

In our previous studies we have shown that somatostatin and octreotide modulate the function of peritoneal macrophages and Kupffer cells in noncirrhotic livers. However, the effects of somatostatin on the Kupffer cells in cirrhotic livers are not known. In the present study, Kupffer cells, obtained from male rats with carbon tetrachloride-induced cirrhotic livers, were treated in vitro with somatostatin or octreotide and their effects on the release of nitric oxide, tumor necrosis factor-alpha (TNF-alpha) and peroxide (H2O2) determined. At concentrations of 10(-13) or 10(-10) to 10(-6) M of somatostatin or 10(-12) to 10(-10) M, or 10(-6) M of octreotide, the amount of nitric oxide released by Kupffer cells was significantly suppressed relative to that of untreated cells. Kupffer cells treated with less than 10(-12) M or greater than 10(-12) M of somatostatin or octreotide released less TNF-alpha compared to the untreated controls. In addition, zymosan-induced H2O2 release by Kupffer cells treated with 10(-9) to 10(-7) M somatostatin or with 10(-15) to 10(-13) M and 10(-9) to 10(-7) M of octreotide was greater than that of the untreated controls. These findings demonstrate that somatostatin and octreotide modulate the release of nitric oxide, TNF-alpha and H2O2 by Kupffer cells in cirrhotic livers depending on the concentrations of hormones used.

Localization of Receptors for Vasoactive Intestinal Peptide, Somatostatin, and Substance P in Distinct Compartments of Human Lymphoid Organs

Regulatory peptides, such as vasoactive intestinal peptide (VIP), somatostatin (SS), or substance P (SP), are considered to play a role in immune regulation. To localize the targets of these peptides in the human immune system, their receptors have been evaluated with in vitro receptor autoradiography in lymph nodes, tonsils, appendix, Peyer's patches, spleen, and thymus. The three peptide receptors were detected in all lymphoid tissues tested, but, unexpectedly, usually in distinct compartments. In lymph nodes, palatine tonsils, vermiform appendix, and Peyer's patches, VIP receptors were found in the CD3 positive zone around lymphoid follicles; SS receptors in the germinal centers of secondary follicles; and SP receptors mainly in interfollicular blood vessels. In the spleen, VIP receptors were detected in periarterial lymphatic sheaths, SS receptors in the red pulp, and SP receptors in the central arteries. In the thymus, VIP receptors were present in cortex and medulla, SS receptors in the medulla, and SP receptors in blood vessels. For comparison, cholecystokinin (CCK)-A and -B receptors were not demonstrated in any of these tissues. These results suggest a strong compartmentalization of the three peptide receptors in human lymphoid tissues and represent the molecular basis for the understanding of a very complex and interactive mode of action of these peptides.

In vitro Leishmania major promastigote-induced macrophage migration is modulated by sensory and autonomic neuropeptides

Recruitment, migration and adherence of macrophages and their interaction with inoculated promastigotes are key steps in the initiation of the inflammatory process in cutaneous leishmaniasis. Parasite- and nervous system-derived factors might be involved in this process. In the present study the chemotactic activities of live, killed and sonicated Leishmania major promastigotes and of the promastigote culture supernatant as well as the L. major surface protease gp63 towards a murine macrophage cell line, Raw 264.7, were investigated, using the Boyden technique. The sensory neuropeptides SOM, CGRP and SP, and the autonomic neuropeptides VIP and NPY, were also investigated for possible modulatory effects on this chemotaxis, using the living promastigotes. Living promastigotes were the most efficient attractants for macrophages compared with other forms of the parasites. Prior incubation of the macrophages with the parasites completely abolished the chemotactic activity. This might indicate that the living promastigote chemotaxis is a receptor-mediated process. On the other hand, paraformaldehyde-killed promastigotes not only failed to induce macrophage chemotaxis but also inhibited it in comparison with the control. The surface protease gp63 tended to inhibit the macrophage chemotactic activity and the sonicate tended to stimulate it compared with controls. The culture supernatant had no effect, indicating that the chemoattractive factors putatively synthesized by the living promastigotes are not released to the surrounding medium. Somatostatin inhibited L. major promastigote-induced macrophage migration at a high concentration, 10(-6) M, while substance P inhibited it at both low concentrations, 10(-10) and 10(-9) M, and a high one, 10(-6) M, the last-mentioned having the greatest inhibitory effect. A stimulatory effect of calcitonin gene-related peptide was found at high concentrations, 10(-5) and 10(-6) M. Vasoactive intestinal peptide stimulated macrophage chemotactic activity at both a high, 10(-5) M, and at a low, 10(-9) M, concentration, the same concentration at which neuropeptide Y exerted its maximum inhibitory effect.

Somatostatin modulates the function of Kupffer cells

Recent studies have shown that somatostatin modulates lymphocyte and peritoneal macrophage function, but the effects of somatostatin on hepatic macrophages (Kupffer cells) are not clearly defined. In the present study, hepatic macrophages obtained from male rats were treated in vitro with somatostatin or octreotide and their effects on the release of nitrite, tumor necrosis factor (TNF), and hydrogen peroxide (H2O2) determined. At concentrations of 10(-14) M to 10(-12) M, or greater than 10(-10) M, somatostatin suppressed nitrite release by Kupffer cells. At concentrations of less than 10(-9) M or greater than 10(-9) M, octreotide inhibited nitrite release by Kupffer cells. Kupffer cells treated with 10(-10) M to 10(-14) M or greater than 10(-8) M of somatostatin released significantly less amounts of TNF than did the untreated controls. TNF release by Kupffer cells treated with 10(-15) M to 10(-5) M of octreotide was significantly inhibited as compared to that of untreated controls. Kupffer cells treated with 10(-14) M to 10(-11) M and 10(-9) M to 10(-8) M of somatostatin released more H2O2 than did the untreated controls. The amount of H2O2 released by noncirrhotic Kupffer cells treated with 10(-6) M or 10(-5) M of somatostatin was less than that of controls. These findings demonstrate that somatostatin and octreotide modulate the release of nitric oxide, TNF, H2O be Kupffer cells depending on the concentration of hormones used.

Histamine selectively enhances human immunoglobulin E (IgE) and IgG4 production induced by anti-CD58 monoclonal antibody

We studied the effects of histamine on human immunoglobulin (IgE) and IgG4 production. Histamine selectively enhanced IgE and IgG4 production in purified surface IgE and IgG4 negative (sIgE-sIgG4-) B cells from normal donors stimulated with interleukin (IL)-4 plus anti-CD58 or IL-13 plus anti-CD58 monoclonal antibody (mAb) without affecting production of IgG1, IgG2, IgG3, IgM, IgA1, or IgA2. In cultures with IL-4 plus anti-CD58 mAb, histamine-induced enhancement of IgE and IgG4 production was specifically blocked by thioperamide (H3 receptor antagonist), and was inhibited by anti-IL-10 antibody (Ab). In contrast, in cultures with IL-13 plus anti-CD58 mAb, histamine-induced enhancement was blocked by dimaprit (H1 receptor antagonist), and was inhibited by anti-IL-6 mAb. Histamine also enhanced IgE and IgG4 production by in vivo-generated sIgE+ and sIgG4+ B cells, respectively, from atopic patients; enhancement was blocked by dimaprit and thioperamide, and was inhibited by anti-IL-6 mAb and anti-IL-10 Ab. In sIgE-sIgG4- B cells, IL-4 plus anti-CD58 mAb induced IL-10 production and IL-10 receptor expression, whereas IL-13 plus anti-CD58 mAb induced IL-6 production and IL-6 receptor expression. Histamine increased IL-10 and IL-6 production without affecting IL-10 and IL-6 receptor expression, in cultures with IL-4 plus anti-CD58 mAb and with IL-13 plus anti-CD58 mAb, respectively, which was blocked by thioperamide and dimaprit, respectively. In contrast, sIgE+ and sIgG4+ B cells spontaneously produced both IL-6 and IL-10 and constitutively expressed IL-6 and IL-10 receptors, and histamine increased IL-6 and IL-10 production without affecting IL-6 or IL-10 receptor expression, which was blocked by thioperamide and dimaprit. These results indicate that histamine enhanced IgE and IgG4 production by increasing endogenous IL-6 and IL-10 production via H1 and H3 receptors, respectively.

RANTES and macrophage inflammatory protein 1 alpha selectively enhance immunoglobulin (IgE) and IgG4 production by human B cells

We studied the effects of various chemokines including neutrophil-activating peptide 2 (NAP-2), beta-thromboglobulin (beta-TG), platelet factor 4 (PF-4), melanoma growth stimulating activity (GRO), gamma interferon-induced protein (IP-10), regulated on activation, normal T expressed and secreted (RANTES), macrophage inflammatory protein 1 alpha (MIP-1 alpha), MIP-1 beta, and monocyte chemotactic protein 1 (MCP-1) on Immunoglobulin (IgE) and IgG4 production by human B cells. None of these chemokines with or without interleukin (IL-4), anti-CD40 or -CD58 monoclonal antibody (mAb), induced IgE and IgG4 production by B cells from nonatopic donors. However, RANTES and MIP-1 alpha selectively enhanced IgE and IgG4 production induced by IL-4 plus anti-CD40 or -CD58 mAb without affecting production of IgM, IgG1, IgG2, IgG3, IgA1, or IgA2, whereas other chemokines failed to do so. Enhancement of IgE and IgG4 production by RANTES and MIP-1 alpha was specifically blocked by anti-RANTES mAb and anti-MIP-1 alpha antibody (Ab), respectively, whereas anti-IL-5 mAb, anti-IL-6 mAb, anti-IL-10 Ab, anti-IL-13 Ab, and anti-tumor necrosis factor-alpha mAb failed to do so. Purified surface IgE positive (slgE4) and slgG4+ B cells generated either in vitro or in vivo spontaneously produced IgE and IgG4, respectively, whereas sIgE- and sIgG4- B cells failed to do so. RANTES and MIP-1 alpha enhanced spontaneous IgE and IgG4 production in slgE+ and slgG4- B cells, respectively, whereas neither RANTES nor MIP-1 alpha did so in sIgE- or sIgG4- B cells. Purified sIgE4+ and sIgG4+, but not sIgE- or sIgG4- B cells, generated in vitro and in vivo expressed receptors for RANTES and MIP-1 alpha, whereas they failed to express receptors for other chemokines. These findings indicate that RANTES and MIP-1 alpha enhance IgE and IgG4 production by directly stimulating sIgE+ and sIgG4+ B cells.

The significance of vasoactive intestinal polypeptide (VIP) in immunomodulation

Evidence for VIP influences on immune function comes from studies demonstrating VIP-ir nerves in lymphoid organs in intimate anatomical association with elements of the immune system, the presence of high-affinity receptors for VIP, and functional studies where VIP influences a variety of immune responses. Anatomical studies that examine the relationship between VIP-containing nerves and subpopulations of immune effector cells provide evidence for potential target cells. Additionally, the presence of VIP in cells of the immune system that also possess VIP receptors implies an autocrine function for VIP. The functional significance of VIP effects on the immune system lies in its ability to help coordinate a complex array of cellular and subcellular events, including events that occur in lymphoid compartments, and in musculature and intramural blood circulation. Clearly, from the work described in this chapter, the modulatory role of VIP in immune regulation is not well understood. The pathways through which VIP can exert an immunoregulatory role are complex and highly sensitive to physiological conditions, emphasizing the importance of in vivo studies. Intracellular events following activation of VIP receptors also are not well elucidated. There is additional evidence to suggest that some of the effects of VIP on cells of the immune system are not mediated through binding of VIP to its receptor. Despite our lack of knowledge regarding VIP immune regulation, the evidence is overwhelming that VIP can interact directly with lymphocytes and accessory cells, resulting in most cases, but not always in cAMP generation within these cells, and a subsequent cascade of intracellular events that alter effector cell function. VIP appears to modulate maturation of specific populations of effector cells, T cell recognition, antibody production, and homing capabilities. These effects of VIP are tissue-specific and are probably dependent on the resident cell populations within the lymphoid tissue and the surrounding microenvironment. Different microenvironments within the same lymphoid tissue may influence the modulatory role of VIP also. Effects of VIP on immune function may result from indirect effects on secretory cells, endothelial cells, and smooth muscle cells in blood vessels, ducts, and respiratory airways. Influences of VIP on immune function also may vary depending on the presence of other signal molecules, such that VIP alone will have no effect on a target cell by itself, but may greatly potentiate or inhibit the effects of other hormones, transmitters, or cytokines. The activational state of target cells may influence VIP receptor expression in these cells, and therefore, may determine whether VIP can influence target cell activity. Several reports described in this chapter also indicate that VIP contained in neural compartments is involved in the pathophysiology of several disease states in the gut and lung. Release of inflammatory mediators by cells of the immune system may destroy VIP-containing nerves in inflammatory bowel disease and in asthma. Loss of VIPergic nerves in these disease states appears to further exacerbate the inflammatory response. These studies indicate that altered VIP concentration can have significant consequences in terms of health and disease. In addition, the protective effects of VIP from tissue damage associated with inflammatory processes described in the lung also may be applicable to other pathological conditions such as rheumatoid arthritis, anaphylaxis, and the swelling and edema seen in the brain following head trauma. While VIP degrades rapidly, synthetic VIP-like drugs may be developed that interact with VIP receptors and have similar protective effects. Synthetic VIP-like agents also may be useful in treating neuroendocrine disorders associated with dysregulation of the hypothalamic-pituitary-adrenal axis, and pituitary release of prolactin.

Somatostatin and macrophage function: modulation of hydrogen peroxide, nitric oxide and tumor necrosis factor release

Recent studies have shown that somatostatin modulates lymphocyte function, but the effects of somatostatin on macrophage function are not clearly defined. In the present study, peritoneal macrophages (Mluminal diameter) obtained from male rats were treated in vitro with somatostatin or octreotide and their effects on the release of hydrogen peroxide (H2O2), nitrite, and tumor necrosis factor (TNF) determined. Macrophages treated with somatostatin (10(-9) M to 10(-7) M) or octreotide (10(-8) M and 10(-7) M) released significantly greater amounts of PMA-stimulated H2O2 than did the untreated controls. In addition, 10(-9) M of somatostatin significantly enhanced PMA-stimulated H2O2 release by LPS-treated Mluminal diameter. Octreotide had no effect on H2O2 release by LPS-treated Mluminal diameter. At concentrations of 10(-14) M, 10(-13) M, or greater than 10(-8) M, somatostatin or octreotide suppressed nitrite release by Mluminal diameter. Somatostatin or octreotide did not affect nitrite release by LPS-treated Mluminal diameter. On the other hand, Mluminal diameter treated with 10(-11) M of somatostatin or octreotide released greater amounts of TNF than did the untreated controls. In contrast, TNF release by Mluminal diameter treated with 10(-9) M to 10(-5) M of somatostatin or 10(-7) M to 10(-5) M of octreotide was less than that of the controls. Anti-TNF antibody (1:1000) caused a reduction in the release of H2O2 and nitrite. These findings demonstrate that somatostatin and octreotide modulate the release of H2O2, nitric oxide, and TNF by Mluminal diameter depending on the concentration of hormones used.

Involvement of interleukin (IL)-13, but not IL-4, in spontaneous IgE and IgG4 production in nephrotic syndrome

Nephrotic syndrome (NS) is a renal disease characterized by proteinuria and hypoalbuminemia. In NS patients without any allergic disease, serum IgE and IgG4 levels were selectively increased, and peripheral blood mononuclear cells (MNC) spontaneously produced IgE and IgG4. T cells produced interleukin (IL)-13 spontaneously, and B cells constitutively expressed IL-13 receptors (IL-13R). In addition, T cells stimulated surface IgE-negative (sIgE-) and sIgG4- B cells to produce IgE and IgG4, respectively, and IgE and IgG4 production was specifically blocked by anti-IL-13 antibody (Ab). MNC from atopic dermatitis (AD) patients also produced IgE and IgG4 spontaneously. However, in AD patients, T cells spontaneously produced IL-4, but not IL-13, and B cells constitutively expressed IL-4R, but not IL-13R. T cells stimulated sIgE- and sIgG4- B cells to produce IgE and IgG4, respectively, and the production was specifically blocked by anti-IL-4 Ab. On the other hand, sIgE+ and sIgG4+ B cells from both NS and AD patients spontaneously produced IgE and IgG4, respectively, and this production was not affected by T cells, anti-IL-4 Ab, or anti-IL-13 Ab. These results indicate that IL-13 is involved in the enhanced production of IgE and IgG4 in NS, while IL-4 is involved in these responses in AD.

Vasoactive intestinal polypeptide and other preprovasoactive intestinal polypeptide-derived peptides in the female and male genital tract: localization, biosynthesis, and functional and clinical significance

Vasoactive intestinal polypeptide, a neuropeptide with wide distribution in the central and peripheral nervous system, has a broad spectrum of biologic actions. The demonstration of vasoactive intestinal polypeptide containing nerve fibers within the female and male genital tract 17 years ago indicated a putative role for this peptide in the local nervous control of reproductive functions. The genes encoding the preprovasoactive intestinal polypeptide precursor molecule and the vasoactive intestinal polypeptide receptor have been identified. The gene expression has been studied by the use of specific antibodies against the functional domains of the vasoactive intestinal polypeptide precursor and the biologic action elucidated by both in vivo and in vitro methods. Evidence has been provided to support vasoactive intestinal polypeptide as a neurotransmitter in several physiologic events in the genital tracts (i.e., blood flow and nonvascular smooth muscle relaxation). In the ovary vasoactive intestinal polypeptide seems to play an important role as regulator and/or modulator of folliculogenesis and steroidogenesis. In the male genital tract vasoactive intestinal polypeptide seems to participate in the control of erection. Vasoactive intestinal polypeptide has been suggested as a causative factor in some diseases of the genital organs (e.g., it may play a pathophysiologic role in male impotence and the peptide is currently used in the treatment of this condition). Vasoactive intestinal polypeptide may be important for control of the low resistance in the fetomaternal vascular bed and is therefore a putative factor involved in the development of preeclampsia. The therapeutic potential of vasoactive intestinal polypeptide and future agonists and antagonists will be revealed by ongoing and forthcoming studies.

Differential effects of gangliosides on human IgE and IgG4 production

The effects of gangliosides on human IgE and IgG4 production were studied. Of the various gangliosides tested, only GM2 and GM3 inhibited the IgE and IgG4 production induced by interleukin (IL)-4 plus hydrocortisone (HC), or that induced by IL-13 plus HC, in human surface IgE- and IgG4-negative (sIgE-, sIgG4-) B cells without affecting the production of IgG1, IgG2, IgG3, IgM, IgA1 or IgA2. In contrast, GM1, GD1a, GD1b, GD3, GT1b and GQ1b were without effects. The GM2- and GM3-mediated inhibition was specific, since each was blocked by a corresponding antibody. Of the various factors tested. IL-6, IL-10, and tumor necrosis factor (TNF)-alpha enhanced the IgE and IgG4 production induced by IL-4 plus HC or by IL-13 plus HC, while IL-8 and transforming growth factor (TGF)-beta inhibited these responses. However, only TNF-alpha counteracted the GM2- and GM3-mediated inhibition of IgE and IgG4 production, while IL-6, IL-10, anti-IL-8 monoclonal antibody and anti-TGF-beta antibody failed to do so. Anti-TNF-alpha monoclonal antibody, but not control IgG1, not only inhibited IgE and IgG4 production in the absence of TNF-alpha but also blocked the counteraction of inhibition by TNF-alpha. In cultures containing IL-4 plus HC or IL-13 plus HC. GM2 and GM3 specifically inhibited TNF-alpha production without affecting TNF-alpha receptors, IL-6 production or IL-6 receptors. These results indicate that GM2 and GM3 inhibit IgE and IgG4 production by inhibiting endogenous TNF-alpha production.

Vasoactive intestinal peptide specifically induces human IgA1 and IgA2 production

The effects of vasoactive intestinal peptide (VIP) on human IgA1 and IgA2 production were studied. In unfractionated small resting B cells stimulated with anti-CD40 monoclonal antibody (mAb), VIP induced IgA1 and IgA2 production without affecting the production of IgG1, IgG2, IgG3, IgG4, IgM, or IgE. When small B cells were separated into sIgA1+, sIgA2+, sIgA1- and sIgA2- B cells, anti-CD40 mAb plus VIP induced IgA1 and IgA2 production by surface IgA1- (sIgA1-) and sIgA2- B cells, respectively, while having no effect on sIgA1+ and sIgA2+ B cells. This induction by VIP was specific, since anti-CD40 mAb plus other neuropeptides, i.e., somatostatin or substance P, had no effect, and moreover, the induction was specifically blocked by a VIP antagonist. Further, anti-CD40 mAb plus various cytokines, including interleukin (IL)-1 beta, IL-2, IL-3, IL-4, IL-5, IL-6, IL-10, transforming growth factor-beta, low molecular weight B cell growth factor, and interferon-gamma, did not induce IgA1 and IgA2 production by sIgA1- and sIgA2- B cells, respectively. These results indicate that in the presence of anti-CD40 mAb, VIP induces IgA1 and IgA2 production by isotype switching.

Growth hormone and insulin-like growth factor I induce immunoglobulin (Ig)E and IgG4 production by human B cells

We studied the effects of growth hormone (GH), insulin-like growth factor I (IGF-I), IGF-II, and insulin on human immunoglobulin E (IgE) and IgG4 production. GH and IGF-I induced IgE and IgG4 production by normal donors' mononuclear cells (MNC) depleted of sIgE+ and sIgG4+ B cells without affecting IgM, IgG1, IgG2, IgG3, IgA1, or IgA2 production, whereas IGF-II and insulin failed to do so. GH-induced IgE and IgG4 production was specific, and was not mediated by IGF-I, interleukin 4 (IL-4), or IL-13, since it was blocked by anti-GH antibody (Ab), but not by anti-IGF-I Ab, anti-IL-4 Ab, or anti-IL-13 Ab. Conversely, IGF-I-induced IgE and IgG4 production was blocked by anti-IGF-I Ab, but not by anti-GH Ab, anti-IL-4 Ab, or anti-IL-13 Ab. Moreover, interferon alpha (IFN-alpha) or IFN-gamma, which counteracted IL-4-and IL-13-induced IgE and IgG4 production, had no effect on induction by GH or IGF-I. In contrast to MNC, GH or IGF-I failed to induce IgE and IgG4 production by purified sIgE-, sIgG4- B cells. However, in the presence of anti-CD40 monoclonal antibody (mAb), GH or IGF-I induced IgE and IgG4 production by these cells. Purified sIgE+, but not sIgE-, B cells from atopic patients spontaneously produced IgE. GH or IGF-I with anti-CD40 mAb failed to enhance IgE production by sIgE+ B cells, whereas they induced IgE production by sIgE- B cells. Similarly, whereas GH or IGF-I with anti-CD40 mAb failed to enhance IgG4 production by sIgG4+ B cells from atopic patients, they induced IgG4 production by sIgG4- B cells. Again, neither IgE nor IgG4 induction was blocked by anti-IL-4 Ab or anti-IL-13 Ab. These results indicate that GH and IGF-I induce IgE and IgG4 production by class switching in an IL-4- and IL-13-independent mechanism.

Vasoactive intestinal polypeptide modulates the in vitro immunoglobulin A production by intestinal lamina propria lymphocytes

BACKGROUND/AIMS

Vasoactive intestinal polypeptide (VIP) modulates the immunoglobulin (Ig) synthesis in the peripheral blood of humans and in various lymphoid organs of other species. Because VIP receptors have been shown on lamina propria mononuclear cells (LPMC), the effects of graded doses of VIP on the in vitro Ig production by normal human LPMC was investigated.

METHODS

Colonic LPMC were cultured with or without graded doses of VIP (1 pmol/L-1 mumol/L). The concentrations of Ig A, G, and M in the 12 days supernatants were quantitated by an enzyme-linked immunosorbent assay, and the effects of VIP were characterized by limiting dilution analysis (LDA).

RESULTS

The addition of VIP was associated with a significant increase in the production of IgA, whereas IgG levels were significantly reduced. Both these effects were restricted to LPMC. LDA showed that the IgA-enhancing effect was associated with an increase in the number of IgA-producing precursor cells and with variation in the regulatory phenomena involved in IgA production.

CONCLUSIONS

In humans, a major function of the mucosal immune system (i.e., the synthesis of IgA) is modulated by VIP. Data suggest that VIP may either act as an indirect switch factor or increase the clone size of pre-committed cells.