A novel homozygous missense ADAMTS13 mutation Y658C in a patient with recurrent thrombotic thrombocytopenic purpura.

Thrombotic thrombocytopenic purpura (TTP) is a devastating systemic disorder that is characterized by microangiopathic hemolytic anemia, thrombocytopenia, neurological dysfunction, and renal failure. In the hereditary form of TTP, severe deficiency of ADAMTS13, a plasma metalloprotease that cleaves von Willebrand factor, is associated with the development of this disorder. A 34-year-old woman was diagnosed with TTP due to severely reduced ADAMTS13 activity; clinical manifestations resolved only by repeated total plasma exchanges or transfusion. Homozygous and heterozygous Y658C (c.1973A>G) alleles were detected in the patient and her child with severe and mild ADAMTS13 deficiencies, respectively. Herein, we report a novel missense mutation Y658C (c.1973A>G) on exon 17 of ADAMTS13 and discuss its clinical implications.

Drug-induced thrombocytopenia.

Drug-induced thrombocytopenia (DIT) is a relatively common clinical disorder. It is imperative to provide rapid identification and removal of the offending agent before clinically significant bleeding or, in the case of heparin, thrombosis occurs. DIT can be distinguished from idiopathic thrombocytopenic purpura, a bleeding disorder caused by thrombocytopenia not associated with a systemic disease, based on the history of drug ingestion or injection and laboratory findings. DIT disorders can be a consequence of decreased platelet production (bone marrow suppression) or accelerated platelet destruction (especially immune-mediated destruction).

[Generation and preliminary application of rabbit anti-human polyclonal antibodies against NH2-terminal peptides of CXCR3-B].

AIM: To generate and identify the rabbit polyclonal antibodies against NH(2)-terminal peptides of CXCR3-B. METHODS: Three peptides (aa. 1 to 19, aa. 17 to 35, and aa. 33 to 51) of human CXCR3-B NH(2)-terminus were synthesized by using standard Fmoc. The synthesized peptides were purified by reversed phase high-performance liquid chromatography (RP-HPLC), and cross-linked with keyhole limpet hemocyanin (KLH) by sodium metaperiodate. Rabbits were immunized with conjugated peptides for 3 times (400 microg/rabbit). The polyclonal antibodies were purified by Protein G from the collected antiserum. RESULTS: NH(2)-terminal peptides of human CXCR3-B with the purity of 98%, 88.54%, and 80%, respectively, were prepared. The titers of purified polyclonal antibodies were 1:32,000 (0.1 mg/L), 1:4,000 (3 mg/L), and 1:1,000 (10 mg/L), respectively. Western blot results showed that the antibodies could recognize the protein with molecular weight of 50,000 in the total lysates of human fetal heart, whereas the antibodies against the peptides of No.1-19 amino acids could also recognize an additional protein (40,000). The antigens recognized by the antibodies were localized in the vascular endothelial cells of human fetal heart tissues. CONCLUSION: The polyclonal antibodies against NH(2)-terminal peptides generated and identified in the present work are specific to CXCR3-B protein and therefore can be useful tools for the functional study of human CXCR3-B.

Platelet factor 4 differentially modulates CD4+CD25+ (regulatory) versus CD4+CD25- (nonregulatory) T cells.

Active suppression mediated by CD4(+)CD25(+) T regulatory (Tr) cells plays an important role in the down-regulation of T cell responses to both foreign and self-Ags. Platelet factor 4 (PF4), a platelet-derived CXC chemokine, has been shown to strongly inhibit T cell proliferation as well as IFN-gamma and IL-2 release by isolated T cells. In this report we show that human PF4 stimulates proliferation of the naturally anergic human CD4(+)CD25(+) Tr cells while inhibiting proliferation of CD4(+)CD25(-) T cells. In coculture experiments we found that CD4(+)CD25(+) Tr cells exposed to PF4 lose the ability to inhibit the proliferative response of CD4(+)CD25(-) T cells. Our findings suggest that human PF4, by inducing Tr cell proliferation while impairing Tr cell function, may play a previously unrecognized role in the regulation of human immune responses. Because platelets are the sole source of PF4 in the circulation, these findings may be relevant to the pathogenesis of certain immune-mediated disorders associated with platelet activation, such as heparin-induced thrombocytopenia and autoimmune thrombocytopenic purpura.