Faculty Collaboration Database

Complexes of heparin and platelet factor 4 specifically stimulate T cells from patients with heparin-induced thrombocytopenia/thrombosis. Blood 1999 Jul 01;94(1):208-15

Date

06/25/1999

Pubmed ID

10381515

Scopus ID

2-s2.0-0033168323 (requires institutional sign-in at Scopus site)   44 Citations

Abstract

Heparin-induced thrombocytopenia with thrombosis (HITT) is associated with antibodies specific for complexes consisting of heparin and platelet factor 4 (PF4). Studies in individual patients with HITT have demonstrated immunoglobulin (Ig) class switching from IgM to the IgG or IgA isotypes. This transition is thought to require helper T cells, but no studies of the cellular or molecular basis of this process have yet been reported. To characterize T-cell involvement in HITT, peripheral blood mononuclear cells (PBMC) from two patients with classical HITT obtained shortly after the acute episode were restimulated with heparin:PF4 complexes, PF4 alone, heparin alone, and medium alone in the presence of autologous antigen-presenting cells (APC). Responding T cells were then examined using the technique of "spectratyping," in which sequences encoding CDR3 domains of individual V beta (BV) families are amplified and separated by gel electrophoresis. After 14 days in culture with antigen (heparin:PF4 complexes), but not after culture with PF4, heparin, or medium alone, patient cells, but not cells from normal subjects, preferentially expressed T-cell receptor (TCR)-containing beta chains of the BV 5.1 family. Nucleotide sequencing of BV 5.1 TCR CDR3 showed that each patient had a personal repertoire, but also shared a tetrapeptide motif (PGTG). These findings provide evidence that the humoral immune response associated with HITT is driven by helper T cells that presumably recognize peptides derived from PF4. Identification of a common beta-chain CDR3 motif in responding T cells from each of two patients suggests that a limited number of helper TCRs may be used to mount an antibody response to heparin:PF4 complexes. TCR spectratyping appears to offer a new way to examine the molecular basis of pathologic immune responses and may be useful in further studies of HITT and other immune-mediated hematologic disorders.

Author List

Bacsi S, De Palma R, Visentin GP, Gorski J, Aster RH

Author

Richard Aster MD Emeritus Professor in the Medicine department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Aged
Amino Acid Sequence
Anticoagulants
Cells, Cultured
Female
Heparin
Humans
Lymphocyte Activation
Middle Aged
Molecular Sequence Data
Platelet Factor 4
T-Lymphocytes
Thrombocytopenia
Thrombosis