Abstract
Abstract Background and Aims Impaired B-cell development has been postulated to play an important role in the maintaining of autoimmune inflammation what makes memory B-cells a perspective target for a new therapeutic strategy in IgA-nephropathy (IgAN). However, to date there are few and controversial data about the precise role of circulating memory B-cell subsets in clinical progression of IgAN. The aim was to estimate the immunological profile of memory B-cell subpopulations in the peripheral blood of IgAN patients. Method The peripheral blood was obtained from 20 IgAN patients (aged of 32.0 (27.0-36.0) y.o., male/female ratio as 13/7) and 15 donors (aged of 38.0 (30.0-46.0) y.o., male/female ratio as 10/5). The diagnosis was confirmed by morphological examination of the biopsy material. The phenotype of B-cells subsets was determined by a panel of CD38-PE/CD19-ECD/CD27-PC5/IgD-APC antibodies; γδT-lymphocytes—by a panel of TCRγδ-FITC/TCRαβ-PE/HLA-DR-ECD/TCRVδ1-PC7/CD3-APC-A750/TCRVδ2-PB/ CD45-KRO antibodies using flow cytometry method (Cytoflex, Beckman Coulter, USA). The concentration of B-cell activating factor (BAFF) was measured using enzyme-linked immunosorbent assay. Statistical data processing was done in Statistica 10.0 program. Results Based on cell surface markers expression the following B-cells subsets were identified in the peripheral blood: naïve B-cells (CD19+CD27−IgD+), pre-switched B-cells (CD19+CD27+IgD+), switched B-cells (CD19+CD27+IgD−), plasmablasts (CD19+CD27+CD38+) and long-lived plasma cells (CD27hiCD38hi) (Fig. 1). The altered balance in B-cells maturation characterizing by a significant lower percent of pre-switched B-cells and plasmablasts (p < 0.05) as well as a higher trend (>55%) in the naive B-cells (p < 0.01) was established in IgAN patients as compared to healthy donors reflecting the exhaustion of peripheral blood plasmablasts due to constant generation of antibody-producing plasma cells. Moreover, the lower pre-switched B-cells percentage was detected in the blood, the more BAFF production was observed in serum of IgAN patients (R = 0.50; p < 0.05) and the higher proteinuria level was detected (R = 0.47; p < 0.05). The increased total number of γδТ-cells up to 9.42 (6.25-12.44)% in IgAN patients as compared to donors (p = 0.03) was correlated with total memory CD19+CD27+B-cells numbers (R = 0.54; p < 0.05) as well as pre-switched B-cells (R = 0.45; p < 0.05), plasmablasts (R = 0.57; p < 0.01) and long-lived plasma cells (R = 0.51; p < 0.05). A detailed subsets analysis revealed an elevated level of tissue-resident mucosa-associated cells (Vδ1+ and Vδ3+T-lymphocytes) as well as enhanced HLA-DR expression on them (p < 0.05) in combination with decreased normally circulating Vδ2+T-cells numbers (p < 0.01) as compared to healthy donors what characterized Vδ1+ and Vδ3+T-cells subsets as professional antigen presenting cells and indicated their possible role in the priming of antigen specific B-cells. Conclusion Suggesting that most peripheral B-lymphocytes are naïve, the obtained data may reflect a γδT-cells role in migration of pre-switched B-cells from the circulation to mucosa sites for possible further maturation and class-switching what allows us to consider these two parameters as potential useful biomarkers of IgAN disease prognosis in clinical practice.
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