Defining a second epitope for heparin-induced thrombocytopenia/thrombosis antibodies using KKO, a murine HIT-like monoclonal antibody.
Journal Article (Journal Article)
Heparin-induced thrombocytopenia/thrombosis (HIT/T) is a common complication of heparin therapy that is caused by antibodies to platelet factor 4 (PF4) complexed with heparin. The immune response is polyclonal and polyspecific, ie, more than one neoepitope on PF4 is recognized by HIT/T antibodies. One such epitope has been previously identified; it involves the domain between the third and fourth cysteine residues in PF4 (site 1). However, the binding sites for other HIT/T antibodies remain to be defined. To explore this issue, the binding site of KKO, an HIT/T-like murine monoclonal antibody, was defined. KKO shares a binding site with many HIT/T antibodies on PF4/heparin, but does not bind to site 1 or recognize mouse PF4/heparin. Therefore, the binding of KKO to a series of mouse/human PF4 chimeras complexed with heparin was examined. KKO recognizes a site that requires both the N terminus of PF4 and Pro34, which immediately precedes the third cysteine. Both regions lie on the surface of the PF4 tetramer in sufficient proximity (within 0.74 nm) to form a contiguous antigenic determinant. The 10 of 14 HIT/T sera that require the N terminus of PF4 for antigen recognition also require Pro34 to bind. This epitope, termed site 2, lies adjacent to site 1 in the crystal structure of the PF4 tetramer. Yet sites 1 and 2 can be recognized by distinct populations of antibodies. These studies further help to define a portion of the PF4 tetramer to which self-reactive antibodies develop in patients exposed to heparin.
Full Text
Duke Authors
Cited Authors
- Li, ZQ; Liu, W; Park, KS; Sachais, BS; Arepally, GM; Cines, DB; Poncz, M
Published Date
- February 15, 2002
Published In
Volume / Issue
- 99 / 4
Start / End Page
- 1230 - 1236
PubMed ID
- 11830470
Pubmed Central ID
- 11830470
International Standard Serial Number (ISSN)
- 0006-4971
Digital Object Identifier (DOI)
- 10.1182/blood.v99.4.1230
Language
- eng
Conference Location
- United States