Intrinsic factor antibody negative atrophic gastritis; is it different from pernicious anaemia?

INTRODUCTION: H. pylori gastritis and autoimmune gastritis are the two main types of chronic atrophic gastritis. Parietal cell antibody (PCA) and intrinsic factor antibody (IFA) are characteristic of autoimmune gastritis, of which IFA is more specific. Patients who are IFA negative are considered under the category of chronic atrophic gastritis. AIM: To differentiate IFA positive from IFA negative chronic atrophic gastritis. METHODS: Fifty consecutive patients of biopsy proven chronic atrophic gastritis were included in this study. All patients underwent haematological and biochemical tests including serum LDH, vitamin B12 and fasting serum gastrin levels. PCA and IFA antibodies were tested in all patients. Multiple gastric biopsies from body and antrum of the stomach were taken and evaluated for presence of intestinal metaplasia, endocrine cell hyperplasia, carcinoid and H. pylori infection. Patients were grouped as group A (IFA positive) and group B (IFA negative). The mean laboratory values and histological parameters were compared between the two groups using appropriate statistical methods. RESULTS: Eighteen patients were in group A (mean age 55.5 +/- 13 years, male: female = 16:2) and thirty-two in group B (mean age 49.7 +/- 13 years, male: female = 25:7). There was no statistically significant difference between median values of haemoglobin, MCV, LDH, Vitamin B12 and serum gastrin in both the groups. None of the histological parameters showed any significant difference. CONCLUSION: There was no statistically significant difference in haematological, biochemical and histological parameters in IFA positive and negative gastritis. These may be the spectrum of the same disease, where H. pylori may be responsible for initiating the process.

Autoantibodies in pernicious anemia type I patients recognize sequence 251-256 in human intrinsic factor.

Pernicious anemia is an organ-specific autoimmune disease characterized by cobalamin deficiency, megaloblastic anemia, neuropathy, and autoimmune gastritis with anti-intrinsic factor autoantibodies. Type 1 anti-intrinsic factor autoantibodies block the cobalamin binding site of the intrinsic factor, a gastric protein required for the assimilation of cobalamin. The aim of our study was to identify the epitope domain of type 1 antibodies. Different series of peptides derived from the intrinsic factor sequence were synthesized and tested for antibody binding in enzyme-linked immunosorbent assay, radioisotope assay, gel filtration, and SDS-PAGE autoradiography. One of these peptides, named IF-R7 (the intrinsic factor aminoacid sequence 251-265), showed a type 1 antibody binding activity and inhibited, in vitro, their blocking activity with Ki at 2.3 microM. The cross-linking of IF-R7 to beta-lactoglobulin produced type 1 anti-intrinsic factor antibodies in immunized sheep. In vivo Schilling tests performed on guinea pigs also revealed IF-R7 peptide inhibition of type 1 antibody blocking activity. 256Ser, 258Lys, 262Tyr and 265Val of the IF-R7 were essential for the epitope recognition. Reactivity with type 1 antibodies was found in IF-R7 homologous peptides from herpesvirus Saimiri and from pathogenic Escherichia coli. In conclusion, the epitope of type 1 anti-intrinsic factor autoantibodies is located in the 251-265 amino acid sequence of the protein. The identification of this epitope will enable the definition of an experimental animal model of anti-IF autoimmunity in order to study the pathogenesis of pernicious anemia.

[Therapy of carcinoids of the stomach]. / Therapie der karzinoide des magens.

Carcinoids of the stomach are rare but have gained importance since the introduction of acid secretion inhibitors. The most important type is the tumor occurring in patients with chronic atrophic gastritis with and without pernicious anemia. The tumors are benign and can be treated by local endoscopic or surgical methods. Antrectomy reduces hypergastrinemia and may cause regression of the tumor. Sporadic carcinoids of the gastric antrum are malignant, however, and require radical surgical treatment.

Schilling test: physiologic basis for and use as a diagnostic test.

With the advent of binding assays for vitamin B12 in blood, the Schilling test, which involves administration of radioactive B12 to a patient and subsequent urine collection for 24 to 48 h, fell into disuse in many laboratories. However, the test is still the only way to actually measure whether vitamin B12 is being absorbed through the terminal ilium. By administering radioactive vitamin B12, along with a preparation of intrinsic factor (IF), lack of functional IF may also be demonstrated. The Schilling test requires that attention be paid to a number of parameters, including the amount of radioactive vitamin B12 administered and the completeness of the urine collection. These factors, and others required for correct performance of the test, are discussed in this article.