Endothelin-1, acting via the A receptor subtype, stimulates thymocyte proliferation in the rat

The adaptation model of immunity: is the goal of central tolerance to eliminate defective T cells or self‐reactive T cells?

The self‐non‐self model and the danger model are designed to understand how an immune response is induced. These models are not meant to predict if an immune response may succeed or fail in destroying/controlling its target. However, these immunological models rely on either self‐antigens or self‐dendritic cells for understanding of central tolerance, which have been discussed by Fuchs and Matzinger in response to Al‐Yassin. In an attempt to address some questions that these models are facing when it comes to understanding central tolerance, I propose that the goal of negative selection in the thymus is to eliminate defective T cells but not self‐reactive T cells. Therefore, any escape from negative selection could increase lymphopenia because of the depletion of defective naïve T cells outside the thymus, as seen in the elderly.

B-lymphocyte-intrinsic and -extrinsic defects in secretory immunoglobulin A production in the neural crest-conditional deletion of endothelin receptor B model of Hirschsprung-associated enterocolitis

Hirschsprung disease (HSCR) is a common cause of intestinal obstruction in the newborn. Hirschsprung-associated enterocolitis (HAEC) is a significant and life-threatening complication of HSCR, affecting up to 60% of patients. Animal models of endothelin receptor B (EdnrB) mutation reliably model human HSCR and HAEC. We previously demonstrated intestinal dysbiosis and a gut-specific deficiency of B-lymphocyte-produced secretory IgA (sIgA), the primary effector molecule of mucosal immunity, in mice with homozygous neural crest cell-conditional deletion of EdnrB (EdnrB^NCC-/-). To determine mechanisms for sIgA deficiency, we examined intrinsic and extrinsic aspects of B-lymphocyte development and function. Expression of the endothelin axis components [endothelin-1 (ET-1), endothelin-3 (ET-3), endothelin receptor A (EdnrA), EdnrB] were determined over a developmental time course. B-lymphocyte survival and Ig production were assayed in vitro. Polymeric Ig receptor (pIgR)-mediated IgA transport into the intestinal lumen was interrogated. We found endothelin axis component (EdnrA, EdnrB, ET-1, ET-3) expression in developing extramedullary hematopoietic organs and that some splenic B lymphocytes express EdnrB. Splenic B lymphocytes from EdnrB^NCC-/- mice showed no intrinsic defect in survival vs. wild-type (WT) B lymphocytes. In vitro stimulation of splenic B lymphocytes demonstrated decreased IgA, IgG, and IgM production in EdnrB^NCC-/- vs. WT mice. Additionally, small intestinal pIgR was decreased ∼50% in EdnrB^NCC-/- mice. These results suggest an intrinsic B-lymphocyte defect in antibody production as well as an extrinsic defect in IgA transport in the EdnrB^NCC-/- model of HAEC. Our results are consistent with human HAEC observations of decreased luminal sIgA and mouse models of other inflammatory bowel diseases, in which decreased pIgR is seen in concert with a dysregulated microbiota. Finally, our results suggest targeting the dysbiotic microbiome and pIgR-mediated sIgA transport as potential therapeutic approaches in prevention and treatment of HAEC.-Medrano, G., Cailleux, F., Guan, P., Kuruvilla, K., Barlow-Anacker, A. J., Gosain, A. B-lymphocyte-intrinsic and -extrinsic defects in secretory immunoglobulinA production in the neural crest-conditional deletion of endothelin receptor B model of Hirschsprung-associated enterocolitis.

A Theoretical Basis for the Efficacy of Cancer Immunotherapy and Immunogenic Tumor Dormancy: The Adaptation Model of Immunity

In the past decades, a variety of strategies have been explored to cure cancer by means of immunotherapy, which is less toxic compared with chemotherapy or radiation therapy, and could establish memory for long-lasting protection against tumor recurrence. These endeavors have been successful in offering therapeutic antibodies, vaccines, or cellular immunotherapies, which resulted in prolonging survival of some cancer patients; however, complete cures have not been consistently achieved. The conception, design, and implementation of these promising immunotherapeutic strategies have been influenced by two schools of thought in immunology, which include the "self-nonself" (SNS) model and the "danger" model. Further progress in cancer immunotherapy to achieve consistent cancer cures requires an evolution in our understanding of how the immune system works. The purpose of this review is to revisit premises and limitations of the SNS and danger models based on the outcomes of cancer immunotherapies by suggesting that both models are two sides of the same coin describing how the immune response is induced against cancer. However, neither explains how the immune response succeeds or fails in eliminating the tumor. To this end, the adaptation model has been proposed to explain efficacy of the immune response for achieving cancer cure.

Impaired Cellular Immunity in the Murine Neural Crest Conditional Deletion of Endothelin Receptor-B Model of Hirschsprung's Disease

Hirschsprung’s disease (HSCR) is characterized by aganglionosis from failure of neural crest cell (NCC) migration to the distal hindgut. Up to 40% of HSCR patients suffer Hirschsprung’s-associated enterocolitis (HAEC), with an incidence that is unchanged from the pre-operative to the post-operative state. Recent reports indicate that signaling pathways involved in NCC migration may also be involved in the development of secondary lymphoid organs. We hypothesize that gastrointestinal (GI) mucosal immune defects occur in HSCR that may contribute to enterocolitis. EdnrB was deleted from the neural crest (EdnrB^NCC-/-) resulting in mutants with defective NCC migration, distal colonic aganglionosis and the development of enterocolitis. The mucosal immune apparatus of these mice was interrogated at post-natal day (P) 21–24, prior to histological signs of enterocolitis. We found that EdnrB^NCC-/- display lymphopenia of their Peyer’s Patches, the major inductive site of GI mucosal immunity. EdnrB^NCC-/- Peyer’s Patches demonstrate decreased B-lymphocytes, specifically IgM⁺IgD^hi (Mature) B-lymphocytes, which are normally activated and produce IgA following antigen presentation. EdnrB^NCC-/- animals demonstrate decreased small intestinal secretory IgA, but unchanged nasal and bronchial airway secretory IgA, indicating a gut-specific defect in IgA production or secretion. In the spleen, which is the primary source of IgA-producing Mature B-lymphocytes, EdnrB^NCC-/- animals display decreased B-lymphocytes, but an increase in Mature B-lymphocytes. EdnrB^NCC-/- spleens are also small and show altered architecture, with decreased red pulp and a paucity of B-lymphocytes in the germinal centers and marginal zone. Taken together, these findings suggest impaired GI mucosal immunity in EdnrB^NCC-/- animals, with the spleen as a potential site of the defect. These findings build upon the growing body of literature that suggests that intestinal defects in HSCR are not restricted to the aganglionic colon but extend proximally, even into the ganglionated small intestine and immune cells.

Trophic factors in the carotid body

The aim of the present study is to provide a review of the expression and action of trophic factors in the carotid body. In glomic type I cells, the following factors have been identified: brain-derived neurotrophic factor, glial cell line-derived neurotrophic factor, artemin, ciliary neurotrophic factor, insulin-like growth factors-I and -II, basic fibroblast growth factor, epidermal growth factor, transforming growth factor-alpha and -beta1, interleukin-1beta and -6, tumour necrosis factor-alpha, vascular endothelial growth factor, and endothelin-1 (ET-1). Growth factor receptors in the above cells include p75LNGFR, TrkA, TrkB, RET, GDNF family receptors alpha1-3, gp130, IL-6Ralpha, EGFR, FGFR1, IL1-RI, TNF-RI, VEGFR-1 and -2, ETA and ETB receptors, and PDGFR-alpha. Differential local expression of growth factors and corresponding receptors plays a role in pre- and postnatal development of the carotid body. Their local actions contribute toward producing the morphologic and molecular changes associated with chronic hypoxia and/or hypertension, such as cellular hyperplasia, extracellular matrix expansion, changes in channel densities, and neurotransmitter patterns. Neurotrophic factor production is also considered to play a key role in the therapeutic effects of intracerebral carotid body grafts in Parkinson's disease. Future research should also focus on trophic actions on carotid body type I cells by peptide neuromodulators, which are known to be present in the carotid body and to show trophic effects on other cell populations, that is, angiotensin II, adrenomedullin, bombesin, calcitonin, calcitonin gene-related peptide, cholecystokinin, erythropoietin, galanin, opioids, pituitary adenylate cyclase-activating polypeptide, atrial natriuretic peptide, somatostatin, tachykinins, neuropeptide Y, neurotensin, and vasoactive intestinal peptide.

Thymic epithelial cells in age-dependent involution

Aging involves morphological and functional alterations within the microenvironment of the thymus where heterogenous populations of thymic epithelial cells (TEC) play the main roles. The studies performed to date on thymic involution signalize a disturbed interaction between individual thymic compartments that disrupt thymocyte-TEC interactions and, as a sequele, disturb differentiation of both TEC and thymocytes. The process of aging affects the various subsets of TEC at different periods of life. Changes in different subsets of TEC are documented on the basis of their phenotypical characteristics, involving morphological analysis and immunocytochemistry. The character and kinetics of changes in TEC are typical for individual subsets and probably sex-dependent. In the course of life, the involutionary changes, expressed by disorganised thymic structure and function, are accompanied by changes in medullary TEC, manifested by alterations in the differentiation process of the cells. In parallel, at the same stage of individual life, the aging process induces increased proliferative and secretory activity of subseptal TEC, which seem to functionally replace medullary TEC. Structural and phenotypic modifications of TEC are locally controlled by complex sets of different factors and seem to represent a morphological adaptation of the gland to the process of aging. Microsc. Res. Tech. 62:488-500, 2003.

Tissue distribution of pneumadin immunoreactivity in the rat

Pneumadin (PNM) is a decapeptide, originally isolated from mammalian lungs, which exerts a potent stimulating effect on arginine-vasopressin (AVP) release, thereby evoking an antidiuretic effect. We have established a specific radioimmunoassay (RIA) method for rat PNM determination, the sensitivity of which is sufficient for measuring tissue content of the peptide. Moreover, raised antibodies have been used for the immunocytochemical detection of PNM in several rat organs. As expected, high concentrations of PNM were detected by RIA in newborn and adult rat lungs and immunocytochemistry (ICC) localized PNM immunoreactivity (IR) in the bronchial and bronchiolar epithelium. Very high concentrations of PNM were measured by RIA in the prostate, and ICC showed that PNM-IR is contained in the epithelial cells. RIA and ICC demonstrated the presence of low amounts of PNM in the thymus. The highest content of radioimmunoassayable PNM was found in the kidneys and intestinal tract, but dilution test suggested the presence of some interfering substances in these tissues. Accordingly, ICC-detectable PNM-IR was absent in the kidneys and present only in the duodenal criptae and Brunner's glands of the intestinal tract. RIA did not measure sizeable PNM concentrations in the thyroid gland, but ICC showed PNM-IR in C-cells. RIA and ICC did not detected PNM in testes, seminal vesicles, ovaries, uterus, pancreas, liver, spleen, adrenal glands, and heart. Taken together, our findings suggest that PNM, in addition to its role as hypothalamo-pituitary AVP secretagogue, may be involved in the autocrine-paracrine functional regulation of other peripheral organs, like lungs and prostate and perhaps duodenum, thymus and thyroid gland.

Adrenomedullin stimulates proliferation and inhibits apoptosis of immature rat thymocytes cultured in vitro

Adrenomedullin (AM) is a hypotensive peptide, which derives from the proteolytic cleavage of pro(p)AM, and acts through two subtypes of receptors, named L1-receptor (L1-R) and calcitonin receptor-like receptor (CRLR). CRLR functions as either a calcitonin gene-related peptide (CGRP) receptor or a selective AM receptor depending on which member of a family of receptor-activity-modifying proteins (RAMPs) is expressed: RAMP1 generates CGRP receptors, while RAMP2 and RAMP3 produce AM receptors. Reverse transcription (RT)-polymerase chain reaction (PCR) consistently allowed the detection of pAM and peptidyl-glycine alpha-amidating monooxygenase (the enzyme converting immature AM to the mature peptide) mRNAs in the thymus cortex of immature (10-day-old) rats. Accordingly, radioimmune assay (RIA) measured low but sizeable AM concentrations in this tissue. RT-PCR also demonstrated the presence of the specific mRNAs of L1-R, CRLR and RAMPs. AM (from 10(-9) to 10(-7)M) increased proliferation index and lowered apoptotic index of cultured immature rat thymocytes, and the effects were annulled by the AM receptor antagonist AM(22-52). In conclusion, our study demonstrated that (1) immature rat thymus cortex expresses AM and the AM receptors L1-R and CRLR/RAMP; and (2) AM, acting via AM(22-52)-sensitive receptors, exerts a potent growth promoting effect on immature rat thymus, by enhancing proliferation and lowering apoptotic death of thymocytes. Taken together, these findings could suggest that AM may play a role in the development of immunity.

Involvement of nuclear factor-kappaB in endothelin-A-receptor-induced proliferation and inhibition of apoptosis

Endothelins have been implicated in the regulation of cell proliferation, differentiation, and apoptosis, but the mechanisms of these complex events are not yet fully understood. Although the nuclear factor-kappaB (NF-kappaB) was shown to play a prominent role in the above processes, its participation in endothelin receptor A (ET(A)R) signaling has not been previously demonstrated. This study provides evidence that NF-kappaB is involved in ET(A)R-induced proliferation and inhibition of apoptosis. Endothelin (ET)-1, ET-3, and sarafotoxin b induce cell proliferation and prevent apoptosis induced by serum deprivation in a Chinese hamster lung (CCL39) cell line that stably expresses ET(A)R (CCL39ET(A)). Activation of ET(A)R resulted in enhanced DNA-binding activity of NF-kappaB and degradation of IkappaB-alpha. Expression of the dominant negative form of IkappaB-alpha (IkappaB deltaN) inhibited the proliferative activities mediated by ET(A)R as well as its anti-apoptotic activities. Treatment of the cells with prostaglandin A1, an inhibitor of IkappaB kinase-beta, reduced ET-1-induced proliferation and its anti-apoptotic effect. These findings indicate that the regulation of cell proliferation and apoptosis by ET(A)R is mediated by the ET(A)R-activated NF-kappaB.

Effects of recombinant murine leptin[1-147] and leptin fragment 116-130 on steroid secretion and proliferative activity of the regenerating rat adrenal cortex

Leptin, the product of the ob gene, is a hormone mainly secreted by the adipose tissue, which acts through specific receptors (Ob-R) widely distributed in the body tissues. Ob-Rs are present in the mammalian hypothalamo-pituitary-adrenal axis, and evidence indicates that leptin regulates adrenocortical secretion. Moreover, leptin is known to act as a growth promoting factor in some tissues, including the endocrine ovary. We have investigated the effects of three subcutaneous injections of 2 nmol/100 g of native murine leptin[1-147] and of its biologically active fragment 116-130 on the secretory and proliferative activity of the regenerating rat adrenal cortex. Leptin[1-147] increased plasma aldosterone concentration at day 8 and plasma corticosterone concentration (PBC) at day 5 of regeneration, without affecting mitotic index. In contrast, leptin[116-130] lowered PBC and mitotic index at both times of adrenal regeneration. In light of the fact that adrenal regeneration is at least in part dependent on the pituitary ACTH, we conclude that: (i) native leptin moderately stimulates steroid secretion, acting directly on the adrenal cortex, through signaling mechanisms other than those involved in the ACTH action; (ii) native leptin is unable to enhance the proliferative activity of regenerating adrenals, which conceivably is maximally stimulated by ACTH; (iii)leptin[1-147] and leptin[116-130] differently interact with Ob-Rs or interact with different receptors; and (iv) leptin[116-130] inhibits the signaling pathways mediating both the secretagogue effect of native leptin and the proliferogenic effect of ACTH.

Effects of galanin on the secretion and proliferative activity of the immature and regenerating adrenal glands of rats

The effects of galanin and the galanin-receptor antagonist (galanin-A) [D-Thr(6),D-Trp(8,9),15-ol]-galanin(1-15) on the immature and regenerating rat adrenal glands have been investigated in vivo. Adult female rats with adrenal regeneration and their offpring (20-day-old) were given three subcutaneous injections (28, 16, and 4 h before being killed) of 2 nmol/100 g galanin and/or galanin-A, and 0.1 mg/100 g vincristin 3 h before being killed. Plasma corticosterone concentration was measured by radioimmunoassay, and the mitotic index ( per thousand of metaphase-arrested cells) was evaluated. In immature rats, galanin increased plasma corticosterone concentration, without affecting mitotic index; the secretagogue effect was reversed by galanin-A, which alone was ineffective. In rats with regenerating adrenal, galanin-A increased both blood level of corticosterone and mitotic index; galanin was ineffective, but blocked the effects of galanin-A. These findings allowed us to draw the following conclusions: 1) galanin exerts a moderate glucocorticoid secretagogue action on immature rat adrenals, but endogenous galanin does not play a major physiological role in the functional control of the gland; and 2) endogenous galanin exerts a maximal tonic inhibitory control on both glucocorticoid secretion and proliferative activity of regenerating rat adrenals, whose physiological relevance remains to be investigated.