The role of Th1/Th2 disbalanced immune response in the determination of clinical features of autoimmune diabetes mellitus
Aim. To elucidate the role of Th1/Th2 polarization of immune response in LADA patients in the realization of the clinical phenotype of the disease. Materials and methods. 70 patients aged 21-61 (mean 41.3+-1.0 yr) with DM diagnosed based on WHO criteria (1999). Groups 1 and 2 included 13 DM1 and 57 DM2 patients (34.6+-7.2 and 43.6+-7.6 yr respectively). 27 DM2 patients (41.2+-1.6 yr) presumably had LADA (P. Zimmet's criteria). Serum anti-GAD65, ICA, and IAA antibodies along with C-peptide were measured in fasting sera and 120 min after GTT by solid phase immunoenzyme assays following manufacturer's instructions with the use of a photometer for Multiscan EX microplates (ThermoLabSystems, Finland) at 405 nm (for GAG and ICA) and 450 nm (for IAA and C-peptide). GAD, IAA, and C-peptides levels were calculated automatically from calibration curves. Mononuclear leukocytes were isolated by centrifugation in the ficoll-verographin density gradient. The cells thus obtained were resuspended in the complete nutritient medium reducing their concentration to 2.0x106/ml. Phytohemagglutinin (Difco, Germany) was added (10 mcg/1 ml) to the samples to stimulate mononuclear leukocytes; cell suspensions were further incubated for 24 hr. Initial and PGA-induced levels of IL-2, 4, 10 in supernatants of cell cultures were measured by solid phase immunoassay at 450 nm. Results. At least one type of autoantibodies (GAD, ICA or IAA) was identified in 24.3% of all DM patients (17/70) and in 18% of the DM2 patients (10/57). The level of anti-GAD and ICA ABs and percentage of AB-positive patients were higher in the LADA group while that of anti-IAA ABs among DM1 patients without LADA. Two AB types at a time were found in 17% (4/23) of the patients with autoimmune DM in the absence of significant difference between LADA and DM1. Patients with LADA had a significantly lower basal C-peptide level than DM2 patients. The was a tendency toward lower level of stimulated C-peptide secretion in LADA patients compared with DM2 ones. It suggests impairment of B-cell secretory function affected by the autoimmune process. We observed enhanced basal production of IFN-y by blood mononuclear leukocytes in all DM patients in the absence of significant difference between the groups. Mitogen-activated production in all CD patients was lower than normal without inter-group differences. Patients with DM2 had the inverted type of IL-2 secretion unlike those with autoimmune diabetes. In both cases it was significantly different from normal values. There was a tendency toward higher basal production of IL-4 by mononuclear leukocytes in LADA and DM2 compared with CD1 which reflects pathogenetic peculiarities of T-cell function in LADA differing from those in DM1 and responsible for slower impairment of B-cell function in this condition. Basal and PGA- induced production of IL-10 was higher in LADA and DM2 than in DM1. It suggests enhanced suppressor activity of leukocytes that may protect B-cells from autoimmune destruction and determines gradual development of clinical symptoms of insulin deficiency. In contrast, low production of IL-10 in DM1 gives evidence of polarization of the immune response. Conclusion. The loss of functional parenchyma and manifestation of insulin deficiency in LADA occur at a relatively low rate due to the peculiar character of cytokine-mediated cell interactions. It suggests the necessity of an active and careful diagnostic strategy with the use of immunological methods for examination of elder patients presenting with a variety of pathogenetic variants of DM.