Intrinsic factor antibodies and intrinsic factor mediated vitamin B-12 absorption in pernicious anaemia

Holo-transcobalamin is an indicator of vitamin B-12 absorption in healthy adults with adequate vitamin B-12 status

BACKGROUND

It has been hypothesized that the response of holo-transcobalamin (holo-TC) to oral vitamin B-12 may be used to assess absorption. To develop a reliable clinical absorption test that uses holo-TC, it is necessary to determine the optimal timeline for vitamin B-12 administration and postdose assessment.

OBJECTIVE

The objective of this study was to assess the magnitude and patterns of change in the postabsorption response of holo-TC to oral vitamin B-12.

DESIGN

Adult (18-49 y) male and female participants (n = 21) with normal vitamin B-12 status were given three 9-mug doses of vitamin B-12 at 6-h intervals beginning early morning (baseline) on day 1. Blood was drawn at 17 timed intervals over the course of 3 d for the analysis of holo-TC and other indicators of vitamin B-12 status.

RESULTS

Mean holo-TC increased significantly (P < 0.001) from baseline at 6 h (11%) and 24 h (50%). TC saturation increased significantly (P < 0.001) from baseline at 12.5 h (33%) and 24 h (50%). The mean cobalamin concentration changed significantly (P < 0.001) from baseline at 24 h (15%) and 48 h (14%). The ratio of holo-TC to cobalamin increased significantly (P < 0.001) at 24 h (32%).

CONCLUSIONS

The greatest increase in holo-TC was observed 24 h after ingestion of three 9-mug doses of vitamin B-12. Our results indicate that a vitamin B-12 absorption test based on measurement of holo-TC after administration of three 9-mug doses of vitamin B-12 should run for 24 h.

Congenital intrinsic factor deficiency in a Spanish patient

Vitamin B-12 deficiency was diagnosed in a 26-year-old man. Examinations performed to determine the etiology of the deficiency showed a vitamin B-12 malabsorption in the Schilling test which was corrected by adding intrinsic factor (IF) as well as normal gastric mucosa and acid secretion, although IF in gastric juice was absent. Family study showed normal serum vitamin B-12 levels in the parents, who are first cousins, and siblings. A gastric examination in the father and the sister showed decreased IF secretion, indicating heterozygosity for the disorder.

Epithelial HLA-DR expression and lymphocyte subsets in gastric mucosa in type B chronic gastritis

Lymphocyte subpopulations (B, T4, T8), monocytes/macrophages (LeuM5, KiM5) and HLA-DR antigen expression were studied immunohistochemically in frozen sections from 32 antral and 37 fundal biopsies of type-B chronic gastritis. Aberrant HLA-DR antigen expression in epithelial cells of gastric mucosa was found in all cases closely related to mononuclear infiltrates. Epithelial HLA-DR expression and mononuclear infiltrates were practically absent in foci of intestinal metaplasia. These findings suggest that an immunopathologic mechanism probably plays a role in initiation or perpetuation of type-B chronic gastritis.

Intrinsic-factor antibody and absorption of vtiamin B12 in pernicious anaemia

The mean urinary excretion in a vitamin-B(12) absorption (Schilling) test in control subjects was 19.2% and in pernicious anaemia when given with additional intrinsic factor was as follows: no intrinsic-factor antibodies demonstrable 19.3%, antibodies in serum only 14.4%, antibodies in gastric juice only 11.1%, and antibodies in both serum and gastric juice 8.4%. It is concluded that intrinsic-factor antibody exerts an adverse effect on vitamin-B(12) absorption in most patients with pernicious anaemia.

Dissociation of intrinsic factor from its antibody: application to study of pernicious anaemia gastric juice specimens

Intrinsic factor antibody may sometimes be concealed in the gastric secretions of pernicious anaemia subjects, being complexed with residual amounts of intrinsic factor.A method is described for dissociating intrinsic factor from its antibody. Antibody to the vitamin-B(12)-binding site of intrinsic factor was identified in 16 (57%) out of 28 samples of pernicious anaemia gastric juice after dissociation but in only 10 before dissociation. There was no clear relationship between the incidence of antibody in the serum and in the gastric juice of these patients.