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.

Immune complexes formed following the binding of anti-platelet factor 4 (CXCL4) antibodies to CXCL4 stimulate human neutrophil activation and cell adhesion.

We tested the possibility that immune complexes formed following platelet factor 4 (PF4/CXCL4) binding to anti-PF4 antibody can stimulate neutrophil activation, similar to previous reports with platelets. Monoclonal Abs against PF4 and IgG from a heparin-induced thrombocytopenia (HIT) patient were applied. We observed that although PF4 or anti-PF4 antibody alone did not alter neutrophil function, costimulation with both reagents resulted in approximately 3-fold increase in cell surface Mac-1 expression, enhanced cell adhesion via L-selectin and CD18 integrins, and degranulation of secondary and tertiary granules.

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.

[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.

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.