Role Of Th1 Cell In The Pathogenesis Of Severe Aplastic Anemia

Preface: Aplastic anemia (AA) is a syndrome characterized by pancytopenia and bone marrow (BM) failure. Although its etiology is not clear, it is suggested that the abnormal immunity might play an important role in the development of AA. To clarify the immune mechanisms of AA, various studies have been conducted. Most of these studies indicated that the T lymphocytes in the blood or BM of patients with aplastic anemia were activated by unknown pathogens. The activated T lymphocytes produce cytokines such as IFN- γ , IL-2 and tumor necrosis factor (TNF) which, especially interferon (IFN)- γ could suppress hematopoiesis, in vitro and in vivo. These cytokines regulated the immune response and hematopietsis. They were mainly produced by CD4~+ T helper (Th) cells, which could be subdivided into two distinct subsets, Th1 and Th2 cells. Th1 cells produced IFN- y and predominantly regalated cell-mediated immune responses. Th2 cells secreted IL-4 and stimulated B-cell proliferation and differentiation to produce predominantly IgGl and IgE antibodies. The balance between Thl and Th2 cells plays important roles in immunity and hematopoiesis. However, little has been known about the role of Th cells in AA patients.Purpose: The present study aims at investigating the quantity, ratio, and function to produce cytokines of Th1 and Th2 cells in SAA and their effects on the hematopoietic failure.Methods: 1) Eleven patients with SAA at diagnosis were observed in Marsh's method for the in vitro cultures of CFU-GM, CFU-E and BFU-E before and after depletion of CD4~+ T lymphocytes from bone marrow mononuclear cells (BMMC); 2) Thl (IFN- γ~+) and Th2 (IL-4~+) cells in peripheral blood of 21 SAA patients and 17 normal controls were counted by FACS. 3) mRNA expression of IFN- γ and IL-4 gene...