Induction of an organ-specific autoimmune disease, lymphocytic hypophysitis, in hamsters by recombinant rubella virus glycoprotein and prevention of disease by neonatal thymectomy

Autoimmune hypophysitis and viral infection in a pregnant woman: a challengeable case

The aim of this study is to report a challengeable and rare case of autoimmune hypophysitis possibly induced by viral infections. A young pregnant female developed optic neuropathy due to enlarged sellar mass responsible for hypopituitarism. Investigations exclude neoplasia and systemic diseases. High level of sedimentation rate and magnetic resonance imaging (MRI) findings supported the diagnosis of autoimmune hypophysitis. The patient reported a history of bronchitis treated with antibiotics and corticosteroids and positive serologies for hepatitis B antigen (Hbs antigen), herpes simplex 1 and rubella. Final examination showed complete recovery of visual function and sellar archnoidocele after antiviral treatment and mild dose of corticosteroids.

Rabphilin-3A as a Targeted Autoantigen in Lymphocytic Infundibulo-neurohypophysitis

CONTEXT

Central diabetes insipidus (CDI) can be caused by several diseases, but in about half of the patients the etiological diagnosis remains unknown. Lymphocytic infundibulo-neurohypophysitis (LINH) is an increasingly recognized entity among cases of idiopathic CDI; however, the differential diagnosis from other pituitary diseases including tumors can be difficult because of similar clinical and radiological manifestations. The definite diagnosis of LINH requires invasive pituitary biopsy.

OBJECTIVE

The study was designed to identify the autoantigen(s) in LINH and thus develop a diagnostic test based on serum autoantibodies.

DESIGN

Rat posterior pituitary lysate was immunoprecipitated with IgGs purified from the sera of patients with LINH or control subjects. The immunoprecipitates were subjected to liquid chromatography-tandem mass spectrometry to screen for pituitary autoantigens of LINH. Subsequently, we made recombinant proteins of candidate autoantigens and analyzed autoantibodies in serum by Western blotting.

RESULTS

Rabphilin-3A proved to be the most diagnostically useful autoantigen. Anti-rabphilin-3A antibodies were detected in 22 of the 29 (76%) patients (including 4 of the 4 biopsy-proven samples) with LINH and 2 of 18 (11.1%) patients with biopsy-proven lymphocytic adeno-hypophysitis. In contrast, these antibodies were absent in patients with biopsy-proven sellar/suprasellar masses without lymphocytic hypophysitis (n = 34), including 18 patients with CDI. Rabphilin-3A was expressed in posterior pituitary and hypothalamic vasopressin neurons but not anterior pituitary.

CONCLUSIONS

These results suggest that rabphilin-3A is a major autoantigen in LINH. Autoantibodies to rabphilin-3A may serve as a biomarker for the diagnosis of LINH and be useful for the differential diagnosis in patients with CDI.

Adenohypophysitis in rat pituitary allografts

The histological, immunohistochemical and ultrastructural alterations in 81 pituitary allografts from Lewis rats transplanted beneath the renal capsule of Wistar rats were investigated. Intrasellar pituitaries of rats bearing allografts were also examined. Recipient rats were sacrificed at various time points after transplantation. Two days after transplantation, the central portion of the allografts demonstrated ischaemic necrosis. A week later, massive mononuclear cell infiltrates consisting primarily of lymphocytes and to a lesser extent, macrophages, plasma cells and granulocytes became prominent. At about three to four weeks after transplantation, the mononuclear cell infiltrate diminished; the surviving adenohypophysial cells, mainly prolactin (PRL) cells, increased in number and necrosis was replaced by connective tissue. No histological changes were noted in the intrasellar pituitaries of rats bearing allografts. Immunohistochemistry demonstrated that the surviving adenohypophysial cells were mainly PRL-producing cells. Electron microscopy revealed adenohypophysial cell destruction, a spectrum of inflammatory cells and, in late phase, accumulation of fibroblasts and collagen fibres. PRL cells were the prominent cell types; they increased in number. It appears that pituitary allografts are 'foreign' and evoke an immune response, suggesting that they may be used as an experimental animal model for morphological investigation of the development and progression of adenohypophysitis, a rare disease occurring mainly in young women often associated with pregnancy.

Induction of experimental autoimmune hypophysitis in SJL mice

Autoimmune hypophysitis can be reproduced experimentally by the injection of pituitary proteins mixed with an adjuvant into susceptible mice(1). Mouse models allow us to study how diseases unfold, often providing a good replica of the same processes occurring in humans. For some autoimmune diseases, like type 1A diabetes, there are models (the NOD mouse) that spontaneously develop a disease similar to the human counterpart. For many other autoimmune diseases, however, the model needs to be induced experimentally. A common approach in this regard is to inject the mouse with a dominant antigen derived from the organ being studied. For example, investigators interested in autoimmune thyroiditis inject mice with thyroglobulin(2), and those interested in myasthenia gravis inject them with the acetylcholine receptor(3). If the autoantigen for a particular autoimmune disease is not known, investigators inject a crude protein extract from the organ targeted by the autoimmune reaction. For autoimmune hypophysitis, the pathogenic autoantigen(s) remain to be identified(4), and thus a crude pituitary protein preparation is used. In this video article we demonstrate how to induce experimental autoimmune hypophysitis in SJL mice.

Lymphocytic hypophysitis with associated thyroiditis in a man with aseptic meningitis

OBJECTIVE

Lymphocytic hypophysitis (LH) is a rare chronic inflammatory disorder characterized by lymphocytic infiltration of the pituitary gland commonly affecting women during pregnancy or post-partum period. The pathogenesis remains uncertain, however an autoimmune process is frequently implicated. There is limited data on the occurrence of LH outside the setting of autoimmunity.

CASE

We describe a 37-year-old man presenting with diarrhoea, nausea, weight loss, low-grade fever, headache and cerebrospinal fluid analysis consistent with aseptic meningitis. Magnetic resonance imaging (MRI) demonstrated a homogenously enlarged pituitary gland with biochemical testing revealing partial hypopituitarism with adenocorticotrophic hormone and gonadotrophin deficiency. Notably, his free thyroid hormone levels were elevated with a suppressed thyroid-stimulating hormone and a suppressed thyroid technetium scan consistent with thyroiditis. Tissue antibodies including thyroid antibodies were negative. Following introduction of hydrocortisone, he developed transient diabetes insipidus which spontaneously resolved after 4 months. Thyrotoxicosis resolved after 5 weeks and thyroxine was commenced as he developed secondary hypothyroidism. Repeat MRI 3 months later showed a reduction in the size of the pituitary gland which by 6 months had returned to normal size. He remains well on hydrocortisone, thyroxine and testosterone replacement.

CONCLUSIONS

Based on clinical and radiological grounds, the diagnosis was consistent with lymphocytic hypophysitis associated with subacute thyroiditis. This is only the second report of this combination in the absence of autoimmunity and the first report of LH and thyroiditis with associated aseptic meningitis in the absence of tissue autoantibodies. We propose a possible viral illness as the unifying aetiological cause.

Autoimmune hypophysitis of SJL mice: clinical insights from a new animal model

Autoimmune hypophysitis (AH) is a rare but increasingly recognized disease of the pituitary gland. Its autoantigens are unknown, and the management is difficult because it is often misdiagnosed as a nonsecreting adenoma. By immunizing female SJL/J mice with mouse pituitary extracts, we established a new mouse model of experimental AH. Immunized mice developed severe lymphocytic infiltration in the anterior pituitary that closely mimicked the human pathology. In the early phase of experimental AH, the pituitary enlarged, consistent with the compression symptoms reported by hypophysitis patients at presentation. In the florid phase, adrenal insufficiency and pituitary antibodies developed, in strong correlation with the pituitary pathology. In the late phase, hypothyroidism ensued, and the pituitary gland became atrophic. Using immune sera as probes in a two-dimensional immunoblotting screen followed by mass spectrometry, we identified several proteins that could function as pituitary autoantigens. These findings provide new insights into the pathogenesis of AH, and establish a platform for developing novel diagnostic biomarkers and therapeutics.

Lymphocytic hypophysitis

BACKGROUND

Lymphocytic hypophysitis is a disorder of the pituitary gland that presents as a sellar mass lesion and/or hypopituitarism. It causes pituicyte destruction and hypopituitarism and is speculated to have an autoimmune basis.

DIAGNOSIS

Lymphocytic hypophysitis should be considered in the differential diagnosis of pituitary masses and/or hypopituitarism in females who are pregnant or in the early postpartum period, especially in cases associated with other autoimmune diseases or unusual patterns of hormone deficiencies. A definitive diagnosis requires tissue biopsy. A presumptive clinical diagnosis can be made based on a history of gestational or postpartum hypopituitarism, a contrast-enhancing sellar mass with imaging features characteristic of lymphocytic hypophysitis, a pattern of pituitary hormone deficiency with early loss of adrenocorticotrophic hormone and thyroid-stimulating hormone unlike that typically found with macroadenomas, relatively rapid development of hypopituitarism and a degree of pituitary failure disproportionate to the size of the mass. Symptoms resulting from partial or panhypopituitarism occur in approximately 80% of cases and multiple deficiencies are found in approximately 75% of cases.

MANAGEMENT

Appropriate management remains controversial. Corticosteroid therapy has been advocated as a means of attenuating inflammation, but given the uncertainty of its efficacy and the known adverse effects, such therapy does not seem justified for most patients. The optimal surgical strategy involves partial resection of the mass to decompress the surrounding structures. All patients with lymphocytic hypophysitis require appropriate replacement therapy for deficient hormones. Long-term follow-up is mandatory to monitor for the development of other hormonal deficits.

Lymphocytic hypophysitis: disease spectrum and approach to diagnosis and therapy

Lymphocytic hypophysitis (LYH) is a neuroendocrine disorder characterized by autoimmune inflammation of the pituitary gland with various degrees of pituitary dysfunction. The histopathology consists of an initial monoclonal lymphocytic infiltrate, which can heal with minimal sequela or progress to fibrosis and result in permanent hypopituitarism. Coexistence of other autoimmune conditions is reported in 25-50% of cases and pituitary autoantibodies have been detected in up to 70% of biopsy-proven cases. The clinical presentation varies depending on the pituitary segment that is more severely affected. In lymphocytic adenohypophysitis (LAH) an early destruction of the ACTH-producing cells is characteristic. Other anterior pituitary hormones can also be affected but posterior pituitary involvement is absent or minimum. Lymphocytic Infundibuloneurohypophysitis (LINH) typically presents as acute onset diabetes insipidus (DI) with intracranial mass-effect symptoms. A combination of extensive anterior pituitary involvement and DI characterizes lymphocytic Infudibulopanhypophysitis (LIPH). The diagnosis can be challenging in many cases, because distinction from pituitary adenomas and other sellar masses is not obvious. Significant efforts have been made to identify specific serum markers, but it would seem unlikely that this approach will ever have the specificity to replace histopathological examination of a surgical specimen. Diagnostic criteria have been proposed to help in the decision-making process and to avoid, whenever possible, unnecessary invasive procedures. The therapeutic approach is controversial and, although transsphenoidal surgery is often performed, a conservative medical management is justified in many cases, given the self-limited nature of the inflammatory process. This paper reviews the etiology, epidemiology, clinical and radiological findings, diagnosis and management of LYH.

Autoimmune hypophysitis

Autoimmune (lymphocytic) hypophysitis is a rare disease that should be considered in the differential diagnosis of any nonsecreting pituitary mass, especially when occurring during pregnancy or postpartum. We have analyzed 370 articles published from January 1962 to October 2004 and identified a total of 379 patients with primary lymphocytic hypophysitis. The present review synthesizes the clinical and research data reported in this body of scientific literature.

Pituitary antibodies and lymphocytic hypophysitis

Lymphocytic hypophysitis (LYH) is a pituitary disease which can cause headache, changes in visual field and pituitary dysfunction. The clinical, histopathological and morphological findings and its association with other autoimmune disorders allow LYH to be included among the autoimmune diseases. Pituitary trans-sphenoidal biopsy is thought to be the diagnostic gold standard for LYH, even if some morphological findings on hypothalamic-pituitary magnetic resonance imaging (MRI) can suggest the occurrence of this disease. Despite the fact that organ-specific antibodies are good markers of many autoimmune endocrine diseases, the pathogenetic and diagnostic roles of anti-pituitary antibodies (APAs) in LYH are still under discussion. In fact, several methods have been used to detect APAs, but the conflicting results from different methods have impaired the clinical relevance of these antibodies. Recently, APAs have been detected by an immunofluorescence method in patients with selective idiopathic hypopituitarism (particularly in those with growth-hormone deficiency) and in adults with autoimmune endocrine diseases. The results suggest that only when they are present at high titres may they be considered a good marker of pituitary involvement, and in particular of growth-hormone-producing cells.

Autoimmune polyglandular endocrinopathy and anterior hypophysitis in a 14 year-old girl presenting with delayed puberty

We report a 14 year-old peripubertal girl who presented at our clinic with the primary complaint of delayed puberty. She was asymptomatic except for vague complaints of fatigue. Physical examination was significant for mucosal hyperpigmentation and lack of secondary sexual characteristics. Laboratory evaluation revealed a morning cortisol concentration of <0.1 microg/dl (normal range [n.r.]: 4.3-22.4 microg/dl) and a simultaneous ACTH concentration of 2 pg/ml (n.r. 25-62 pg/ml); FSH 66.8 IU/l (n.r. for age: 1-12.8 IU/l); LH 41.1 IU/l (n.r. for age: 1-12 IU/l); E2 38 pg/ml (n.r. for age: 7-60 pg/ml). She had a flat cortisol response to an ACTH stimulation test. MRI of the pituitary gland failed to reveal a lesion. Plasma renin activity, thyroid function tests, parathyroid hormone, prolactin, IGF-I, IGFBP-3 concentrations and serum electrolytes were normal. However, her urinary sodium concentration was high. She was diagnosed with autoimmune polyglandular endocrinopathy including ovarian failure, adrenal failure and autoimmune anterior hypophysitis presenting as isolated ACTH deficiency. We emphasize that autoimmune etiology should be considered in the differential diagnosis of delayed puberty and ovarian failure and that the presence of other endocrinopathies should be searched for even in asymptomatic patients.

Postpartum pituitary hypophysitis

The case of a young woman who developed lymphocytic hypophysitis 2 weeks after delivery of a healthy baby is reported. The patient presented with clinical features suggestive of a pituitary mass lesion, but surgery was avoided when other clinical and radiologic features were considered. The patient recovered with steroid treatment only. We review the literature on this increasingly recognized condition and argue that medical management may be more suitable than previously thought.

Acute loss of vision during pregnancy due to a suprasellar mass

A pregnant woman presented with headaches, bilateral decreased visual acuity, and a central scotoma with a superotemporal hemianopic defect in the right eye and a superotemporal hemianopic defect in the left eye, and bilateral temporal optic disk pallor. Neuroimaging revealed an intrasellar mass with suprasellar extension. Biopsy of the lesion revealed lymphocytic hypophysitis (LH). Treatment with steroids produced marked improvement in visual function. The clinical presentation of lymphocytic hypothysitis may mimic pituitary adenoma and the diagnosis should be suspected in any pregnant or postpartum patient with an intrasellar or suprasellar mass.

Autoimmune hypophysitis

Autoimmune (lymphocytic) hypophysitis has emerged as a distinct and specific clinical and pathological disease entity. Although relatively rare compared with other autoimmune endocrine diseases, nearly a hundred cases have been described. The condition is much more common in females (9:1) and appears to have a particular predilection for the pregnant and postpartum states. The anterior pituitary, and less often the neurohypophysis, appear to be the target for inflammatory autoimmune destruction. During the evolution of the disease process, pituitary hyperfunction (usually hyperprolactinemia) has been noted. This disease should now be included in the differential diagnosis of pituitary disorders, especially in females presenting with pituitary enlargement, particularly if symptoms occur in temporal relationship to pregnancy. The disease may form part of the spectrum of the polyglandular autoimmune endocrine disorders. (Trends Endocrinol Metab 1997;8:74-80). (c) 1997, Elsevier Science Inc.

Lymphocytic Hypophysitis Presenting as a Pituitary Tumor in a 63-Year-Old Man

This report describes a case of lymphocytic hypophysitis in a 63-year-old man who presented with symptoms of a pituitary mass lesion associated with hypothyroidism and hypogonadism. Postoperative endocrinologicaI testing demonstrated gonadotropic, thyrotropic, and corticotropic hypopituitarism, and the patient was commenced on replacement therapy with hydrocortisone and levothyroxine. Histological examination of the pituitary tissue obtained by transsphenoidal surgery revealed lymphocytic hypophysitis without evidence of a pituitary adenoma. The vast majority of patients with lymphocytic hypophysitis are women particularly during pregnancy and the puerperium. Until recently only four men were reported in the literature. The pathogenesis of lymphocytic hypophysitis is uncertain but autoimmune mechanisms are possibly involved.

Lymphocytic hypophysitis

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Identification of immunoreactive regions of rubella virus E1 and E2 envelope proteins by using synthetic peptides

Relatively large (16-33 aa) synthetic peptides (SPs) representing defined sequences of rubella virus (RV) E1 and E2 envelope proteins were used in lymphocyte stimulation and enzyme immunoassays to map immunoreactive regions recognized by peripheral blood mononuclear cells (PBMNC) and serum antibodies from healthy RV-seropositive, RV-seronegative, and RV-vaccinated adults. Five distinct immunoreactive regions were identified in RV E1 protein, spanning residues (11-39), (154-179), (199-239), (226-277), and (389-412), which stimulated cellular responses in 29-83% of the subjects tested. Two SPs, E1(213-239) and E1(258-277) containing previously-identified virus neutralizing antibody domains, reacted with serum antibodies and also stimulated lymphoproliferation suggesting that these E1 sequences contain linked or overlapping B-and T-cell antigenic sites. The frequency and magnitude of cellular responses to E2 SPs were somewhat lower. SPs encompassing E2 residues (50-72), (140-199), and (244-263) stimulated lymphocyte responses in 28-64% of the subjects tested, while to a lesser degree, SPs within residues (1-36) were also stimulatory. E2 SPs within the regions (1-36), (151-170), and (244-263) also showed low levels of antibody reactivity with sera from RV-seropositive subjects. E2(244-263) which induced the highest level of response among the E2 SPs tested, was of interest due to previous reports of sequence homology of this RV region with human myelin and its potential immunopathogenic role in demyelinating autoimmune diseases. Identification of these potentially immunodominant regions of RV envelope proteins is an important first step in the rational design of new RV vaccines.

Mapping T-cell epitopes of rubella virus structural proteins E1, E2, and C recognized by T-cell lines and clones derived from infected and immunized populations

To design a safe and effective synthetic peptide vaccine against rubella virus (RV) infection, it is necessary to identify immunodominant T-cell epitopes of RV structural proteins. To define such epitopes, 49 overlapping synthetic peptides (17-34 residues in length) corresponding to more than 95% of the amino acid sequence of RV virion proteins E1 (23 peptides) and C (11 peptides) and all of E2 (15 peptides) were synthesized and tested for their capacities to induce proliferative responses of rubella-specific T-cell lines and T-cell clones derived from 4 study groups (5 women infected with RV in pregnancy, 5 patients with congenital rubella syndrome, 5 seropositive healthy donors, and 5 RV vaccine recipients). The most frequently recognized epitopes were E1-21 (residues 358-377) with 11/20 responders, E2-4 (residues 54-74) with 6/20 responders, and C11 (residues 255-280) with 11/20 responders, respectively. E1-10 (residues 174-193), E1-16 (residues 272-291) and E1-18 (residues 307-326) were responded to strongly by corresponding T-cell clones, and were recognized by 4 or 5 T-cell lines. T-cell lines derived from three congenital rubella syndrome patients did not respond to any of the synthetic peptides. The results showed that more T-cell epitopes were present in E1 (19/23) and C (10/11) than in E2 (8/15). The identification of T cell sites recognized frequently by RV-infected or -immunized populations could provide the basis for selecting candidate T-cell epitopes for the development of an effective synthetic vaccine against rubella.