A murine model for human immune thrombocytopenic purpura and comparative analysis of multiple gene expression in bone marrow and spleen

Decreased plasma cytokines are associated with low platelet counts in aplastic anemia and immune thrombocytopenic purpura

BACKGROUND

We previously found plasma levels of CD40 ligand (CD40L), chemokine (C-X-C motif) ligand 5 (CXCL5), chemokine (C-C motif) ligand 5 (CCL5) and epidermal growth factor (EGF) to be low in aplastic anemia (AA) patients and to be correlated with platelet count.

OBJECTIVES

To study the association of CD40L, CXCL5, CCL5 and EGF with platelets.

METHODS

We measured cytokines in the plasma of immune thrombocytopenic purpura (ITP) and AA patients using the Luminex assay and confirmed the results in a mouse model and in vitro experiments.

RESULTS

Both ITP and AA showed similarly low levels of CD40L, CXCL5, CCL5 and EGF, compared with healthy controls. In ITP, levels of these proteins were significantly greater in patients with higher platelet counts than in those with lower platelet counts. In a murine thrombocytopenia model, levels of CD40L, CXCL5, CCL5 and EGF decreased with platelet count after immune-mediated destruction, while the cytokine levels increased when the platelet count recovered. In vitro, concentrations of these cytokines in the supernatants of platelet suspensions were proportional to platelet numbers, and levels in sera prepared by simple blood coagulation were equivalent to those in platelet-rich plasma-converted sera. mRNA expression for CXCL5, CCL5 and EGF was higher in platelets than in megakaryocytes, peripheral blood mononuclear cells, granulocytes and non-megakaryocytic bone marrow cells.

CONCLUSIONS

Plasma CD40L, CXCL5, CCL5 and EGF are mainly platelet-derived, suggesting a role of platelets in immune responses and inflammation. Measurement of CD40L, CXCL5, CCL5 and EGF in human blood allowed testable inferences concerning physiology and pathophysiology in quantitative platelet disorders.

Animal models of immune thrombocytopenia (ITP)

With regards to research animal models related to immune thrombocytopenia (ITP), there is an extensive literature of over 300 publications published since 1959. It appears that many of these models either confirm what has been found in human ITP or, in some instances, are the first to describe a phenomenon related to ITP that is still of relevance today in human medicine. These models will undoubtedly play a significant role in the future research of human ITP particularly related to understanding of the pathogenesis of the disorder and the development of novel therapeutics. This review will highlight some of the major animal models utilized for ITP research and will present a somewhat historical aspect of the subject.