Significant association between clinical characteristics and immuno-phenotypes in patients with ANCA-associated vasculitis

Objectives: To elucidate the association between clinical characteristics and immuno-phenotypes in patients with ANCA-associated vasculitis (AAV). Methods: Peripheral blood from 36 patients with active AAV and 18 healthy controls was examined for numbers of circulating T cells, B cells, NK cells, dendritic cells, monocytes and granulocytes using flow cytometry. These immuno-phenotyping data were subjected to cluster analysis and principal components analysis to divide AAV patients into subgroups. Associated organ involvement or therapeutic prognosis were assessed for each subgroup. Results: AAV patients had higher proportions of plasma cells, plasmablasts, activated T cells, CD14⁺⁺ CD16⁺ monocytes, eosinophils and neutrophils than healthy controls. Immuno-phenotyping findings were similar between patients with microscopic polyangiitis, granulomatosis with polyangiitis and eosinophilic granulomatosis with polyangiitis. Cluster analysis indicated that AAV patients could be divided into three subgroups according to peripheral immune cell numbers: antibody production-related (n = 9), cytotoxic activity-related (n = 4) and neutrocytosis/lymphocytopenia-related (n = 23). The antibody production-related or cytotoxic activity-related group was associated with CNS involvement, and the neutrocytosis/lymphocytopenia-related group was associated with high incidence of kidney involvement. Incidence of severe infection was markedly higher in the neutrocytosis/lymphocytopenia-related group than the other two groups. Incidence of disease relapse was comparable among the three groups. Conclusion: Patients with active AAV can be divided into three subgroups based on immuno-phenotyping. These results may provide a hint to understanding disease pathophysiology and prognosis, and determining appropriate treatment.