الفهرس | Only 14 pages are availabe for public view |
Abstract Summary Primary immune thrombocytopenia (ITP) is an autoimmune disorder caused by both increased peripheral platelet destruction and impaired platelet production and is usually characterized by platelet counts less than 100 × 10 ⁹ /L. It often occurs in children following a viral or bacterial infection and self-resolves. Production of autoantibodies against platelet glycoproteins (GP) and opsonization with these autoantibodies lead to platelet clearance by the reticuloendothelial system. Autoantibodies production often occurs due to the loss of self-tolerance and increased stimulation of the immune system. Antibody responses are largely dependent on the help provided by CD4+ T cells.Recently, CD4+ T cells present in B cell follicles, named T follicular helper (Tfh) cells, which is identified by expression of the B cell follicle homing receptor CXCR5. Tfh cells trigger the formation and maintenance of germinal centers through the expression of CD40 ligand (CD40L) and the secretion of IL- 21 and IL-4. Tfh cells play a critical role in mediating the selection and survival of B cells that go on to differentiate either into special plasma cells capable of producing high affinity antibodies against foreign antigen, or memory B cells capable of quick immune re-activation in the future if ever the same antigen is re-encountered. Autoimmune diseases are caused by a breakdown of immune tolerance. Proliferation of self-reactive B cells with generation of high-affinity autoantibodies participate to the pathophysiology of |