IgG autoantibody subclasses altered in immuno-related hemocytopenia

Recently, we have detected autoantibodies to bone marrow (BM) hemopoietic cells in some idiopathic cytopenia of undetermined significance (ICUS), terming as immunorelated hemocytopenia. Immunoglobulin G consists of 4 subclasses which have different biological functions in many diseases. In this study, we analyzed the alterations of IgG subclasses in 27 IRH patients compared with 20 ICUS patients and 20 normal controls. The results showed that IgG1 and IgG3 levels were increased in the bone marrow supernatant in IRH patients, and had inverse correlations with hematopoietic function. Meanwhile IgG1 level had a positive correlation with the proportion of CD5+ B lymphocytes. Using immunohistochemical staining, IgG1 were also detected on bone marrow nucleated cells in IRH patients. All these results indicated that IgG1 on bone marrow cells in some IRH patients might be involved in the destruction of hematopoietic cells leading to cytopenia and might be a novel therapeutic target in future.