Megakaryocytes and platelets in immune thrombocytopenic purpura.
In idiopathic thrombocytopenic purpura, 90% of the patients have an elevated platelet-associated immunoglobulin. The most important related antigens are glycoprotein IIb-IIIa (GPIIb-IIIa) (16.7-83.3%), GPIb-IX (13.3-83%), GPIb (3.3-47.1%) and GPIIIa (21.6-33.3%), and less commonly GPIa-IIa, GPIV and GPV. Other related antigens can be platelet granule membrane protein, phospholipid, intraplatelet and cytoplasmic antigens, and rarely human platelet antigen (HPA) 1a and HLA-DR antigens. The marrow megakaryocytes are usually normal or increased in number with maturation impairment. There are discrepancies regarding megakaryocytopoiesis in vitro. A low dose of heparin could elevate the platelet number in certain cases. The expression of c-sis was reported to be inhibited in ITP, when the plasma beta-thromboglobin-platelet factor 4 level was elevated. In secondary immune thrombocytopenia, platelet antibodies can be (1) alloantibodies against the (HPA) system and (2) autoantibodies most commonly against platelet GPIIb-IIIa or GPIb-IX. Other antigens can be 30-52kDa proteins of the platelet membrane. Platelet survival is usually shortened, and marrow megakaryocytes are normal in number. Megakaryocyte colony-forming units could be reduced.
Wang
Z Y
ZY
Department of Haematology, Shanghai Institute of Haematology, Rui-jin Hospital, Shanghai Second Medical University, People's Republic of China.
Shen
Z X
ZX
D001792:Blood Platelets / Q000276:immunology* / Q000473:pathology; D016026:Bone Marrow Transplantation / Q000009:adverse effects; D006801:Humans; D007231:Infant, Newborn; D007239:Infections / Q000150:complications; D008533:Megakaryocytes / Q000276:immunology* / Q000473:pathology; D009369:Neoplasms / Q000150:complications; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000276:immunology* / Q000473:pathology; D013921:Thrombocytopenia / Q000209:etiology / Q000276:immunology; D065227:Transfusion Reaction