Lymphocyte subpopulations in patients with untreated pernicious anaemia

Effects of cyanocobalamin on immunity in patients with pernicious anemia

OBJECTIVE

The aim of the study was to evaluate the role of vitamin B(12) in patients with pernicious anemia.

MATERIALS AND METHODS

This study was conducted prospectively at the Turgut Ozal Medical Center, Department of Hematology, between April and November 2002. Absolute numbers and ratio of the surface antigens of T and B lymphocyte subgroups, CD4/CD8 ratio were calculated in order to evaluate changes in leukocyte and lymphocyte numbers; natural killer (NK) cell count, serum C3, C4, and levels of immunoglobulins G, A, and M were also measured to evaluate vitamin B(12) effect on immunity. Values obtained before treatment with cyanocobalamin were compared with those found during peak reticulocyte count.

RESULTS

In vitamin B(12)-deficient patients, absolute numbers of CD4+ and especially CD8+ lymphocytes were found to be decreased; CD4/CD8 ratio increased, and NK cell activity was depressed. After cyanocobalamin treatment, absolute numbers and percentage of lymphocyte subgroups were elevated. Increased CD4/CD8 ratio and depressed NK cell activity were restored and levels of C3, C4, and immunoglobulins were elevated.

CONCLUSION

These findings suggest that vitamin B(12) has important immunomodulatory effects on cellular immunity, and abnormalities in the immune system in pernicious anemia are restored by vitamin B(12) replacement therapy.

Immunomodulation by vitamin B12: augmentation of CD8+ T lymphocytes and natural killer (NK) cell activity in vitamin B12-deficient patients by methyl-B12 treatment

It has been suggested that vitamin B12 (vit.B12) plays an important role in immune system regulation, but the details are still obscure. In order to examine the action of vit.B12 on cells of the human immune system, lymphocyte subpopulations and NK cell activity were evaluated in 11 patients with vit.B12 deficiency anaemia and in 13 control subjects. Decreases in the number of lymphocytes and CD8+ cells and in the proportion of CD4+ cells, an abnormally high CD4/CD8 ratio, and suppressed NK cell activity were noted in patients compared with control subjects. In all 11 patients and eight control subjects, these immune parameters were evaluated before and after methyl-B12 injection. The lymphocyte counts and number of CD8+ cells increased both in patients and in control subjects. The high CD4/CD8 ratio and suppressed NK cell activity were improved by methyl-B12 treatment. Augmentation of CD3-CD16+ cells occurred in patients after methyl-B12 treatment. In contrast, antibody-dependent cell-mediated cytotoxicity (ADCC) activity, lectin-stimulated lymphocyte blast formation, and serum levels of immunoglobulins were not changed by methyl-B12 treatment. These results indicate that vit.B12 might play an important role in cellular immunity, especially relativing to CD8+ cells and the NK cell system, which suggests effects on cytotoxic cells. We conclude that vit.B12 acts as an immunomodulator for cellular immunity.

Lymphocyte surface phenotypes in pernicious anemia

Because an immunological defect of an unknown nature is thought to be a factor in the pathogenesis of pernicious anemia, we studied lymphocyte surface phenotypes in 40 patients and compared them with 113 healthy controls. The only significant difference that emerged was in their slightly decreased number and proportion of surface immunoglobulin (lambda chain) -bearing cells. Of specific interest, the numbers of OKT4+ and OKT8+ lymphocytes and the T4+/T8+ ratios were not significantly different from control values. A sizable minority of patients had increased ratios, while a smaller number had decreased values. No explanation or identifying feature was apparent for those patients with either increased or decreased T4+/T8+ ratios. (One patient with a very low ratio, who was excluded from our analysis, developed acquired immune deficiency syndrome.) No differences were apparent in T4+/T8+ ratios or any other lymphocyte surface phenotypic characteristics when patients were segregated by presence of anti-intrinsic factor antibody or anti-parietal cell antibody, or by race, sex, or age. Our results in a racially heterogeneous group of patients do not support the suggestion that T4+/T8+ ratios are usually abnormal in prenicious anemia or that the presence of anti-intrinsic factor antibody is associated with such abnormality.

Immunological aspects of gastritis and pernicious anaemia

Pernicious anaemia (PA) and chronic atrophic gastritis (CAG) aggregate in families, occur more often in women, and are associated with various heritable traits such as fair skin and blue eyes. They are linked to certain HLA types. Linkages are relatively weak for A and B antigens, but somewhat stronger in the case of DR antigens. There are strong associations between PA and other organ-specific autoimmune diseases, particularly those affecting the thyroid. Discordance for PA in monozygotic twins has been reported, and it may well be that expression of the disease requires, in a genetically susceptible individual, initial injury to the gastric mucosa by some environmental agent such as a virus or some physical irritant, with perpetuation of injury then depending upon autoimmune mechanisms. Numbers of T cells are substantially increased in the gastric mucosa of patients with PA, but the ratio of T suppressor to T helper cells is normal. There is a relatively greater increase in numbers of cells not of T lineage, presumably B-cells. Gastric autoantibodies, both to different components of the parietal cell and to two sites on the IF molecule, are present in a majority of patients with PA. There is evidence that these autoantibodies, especially PCA, may be cytotoxic to parietal cells, and may also inhibit their maturation and proliferation. Antibodies to chief cells have not been described, and the parallel disappearance of these cells in atrophic gastritis is unexplained. The peripheral blood lymphocytes of some patients with autoimmune gastritis transform, or produce lymphokines, when exposed to gastric antigens, and patients with PA have been shown to have delayed type cutaneous hypersensitivity to gastric antigens. The relevance of these observations to the pathogenesis of their gastric mucosal lesion is unclear. There is a growing body of evidence to support the operation of humoral immune mechanisms in autoimmune gastritis, but this clearly does not preclude the coexistent involvement of cellular mechanisms. For example, impaired suppressor T cell function has been strongly implicated in certain other autoimmune disorders, but has received scant attention in PA. By generally accepted criteria, PA is an excellent example of an organ-specific autoimmune disease. As yet, there is no acceptable single unifying hypothesis which will account for all of the phenomena which have been described in the disease.(ABSTRACT TRUNCATED AT 400 WORDS)