High levels of thrombopoietin in sera of patients with essential thrombocythemia: cause or consequence of abnormal platelet production?

Thrombopoietin (TPO) is the most important regulator of megakaryocyte development and platelet production. Platelet production is thought to be regulated by a negative regulatory feed back loop. In an attempt to evaluate the role of TPO in the pathobiology of essential thrombocythemia (ET), we have examined levels of TPO and other cytokines with thrombopoietic activity (interleukin-6 and interleukin-11) in sera obtained from 25 patients with ET (ten treated, 15 untreated) and 117 healthy control subjects.

Thrombopoietin serum levels in patients with aplastic anaemia: correlation with platelet count and persistent elevation in remission.

In an attempt to evaluate the role of thrombopoietin (TPO) in the pathobiology of aplastic anaemia (AA), we have examined TPO levels in sera from 54 AA patients and 119 healthy controls. A total of 92 samples were collected from AA patients: 43 samples were harvested at diagnosis, 23 samples in the cytopenic period after treatment, and 26 samples when patients were in partial (n=10) or complete remission (n=16) following immunosuppressive treatment. TPO serum levels were assessed by a sandwich-antibody ELISA that utilized a polyclonal rabbit antiserum for both capture and signal.

Thrombopoietin level in young patients is related to megakaryocyte frequency and platelet count.

Purpose: To examine the relationships among platelet counts, bone marrow megakaryocyte frequency, and circulating thrombopoietin (TPO) levels.

Patients And Methods: TPO levels in 17 children and one young adult with chronic or recurrent thrombocytopenia were measured by ELISA and megakaryocyte frequency was analyzed by light microscopy. Three groups of patients were studied: Group I patients had aplastic anemia and absent or decreased megakaryocytes; Group II patients had intermittent periods of chemotherapy-induced thrombocytopenia; and Group III patients had normal or increased megakaryocytes.

Serum thrombopoietin levels in patients with aplastic anaemia.

Endogenous serum thrombopoietin (TPO) levels were measured in 31 patients with aplastic anaemia (AA) using an enzyme immunoassay with a sensitivity of 20 pg/ ml. The median platelet count for all AA patients was 30 +/- 29 x 10(9)/l (range 5-102) compared with a median of 284 +/- 59 x 10(9)/l (range 148-538) for normal controls. Serum TPO levels were significantly elevated in all patients compared with normals (1706 +/- 1114.

Purification and biologic characterization of plasma-derived megakaryocyte growth and development factor.

The isolation and cloning of the ligand for the cytokine receptor, Mpl, have been recently described. In this report we present details of the purification of this novel cytokine (megakaryocyte growth and development factor [MGDF]) from aplastic canine plasma. Two forms of canine MGDF, with apparent molecular weights of 25 kD and 31 kD and sharing a common N-terminal amino acid sequence, were isolated.