Anti‐CD36 autoantibodies in thrombotic thrombocytopenic purpura and other thrombotic disorders: identification of an 85 kD form of CD36 as a target antigen

Abstract

Summary. The presence of anti-CD36 antibodies in plasma of patients with thrombotic thrombocytopenic purpura (TTP), idiopathic thrombocytopenic purpura (ITP), and heparininduced thrombocytopenia without/with thrombosis (HIT/ HITT) has been examined by immunoblots, and a monoclonal antibody capture assay, the platelet-associated IgG characterization assay (PAICA). Results with PAICA showed that 73% (8/11) of patients with TTP were positive, and 71% (10/14) by immunoblots. With ITP, 20% (6/30) were positive by PAICA and 19% (3/16) by immunoblots; HIT, 30% (3/10) were positive by PAICA and 60% (6/10) by immunoblot; HITT, 50% (2/4) by PAICA and 100% (4/4) by immunoblot. Purification of CD36 by fast protein liquid chromatography (FPLC) from Triton X-100 extracts of normal platelet membranes resulted in the isolation of two different forms: the classic 88 kD form, and a second, lighter 85 kD form. Our data indicated that the patients' plasma autoantibodies reacted strongly with the 85 kD form. Conventional monoclonal and polyclonal antisera produced to the 88 kD form reacted strongly with the 88 kD form but weakly with the 85 kD form. These results confirm the possible importance of anti-CD36 antibodies in the pathophysiology of TTP and other thrombocytopenias and demonstrate the presence of a previously unrecognized target antigen for these antibodies.Keywords: thrombosis, thrombocytopenia, platelets, glycoform, immunoassays.The human CD36 is a single-chain integral membrane polypeptide (also known as GPIV; IIIb) expressed by platelets as well as many other cells, cell lines and tissues (Okumura & Jamieson, 1976;Asch et al, 1987;Tandon et al, 1989b;Greenwalt et al, 1990Greenwalt et al, , 1992. Numerous functions have been described for CD36, including a role as a cell surface receptor interactive with a large number of ligands, in cytoadhesion reactions, and implication in intracellular signal transduction (Jaffe et al, 1982;Leung, 1984;Silverstein et al, 1984Silverstein et al, , 1989Majack et al, 1988;Kieffer et al, 1989; Tandon et al, 1989a,b;Good et al, 1990;Murphy-Ullrich et al, 1992;Savill et al, 1992;Greenwalt et al, 1992;Endemann et al, 1993;Abumrad et al, 1993;Kehrel et al, 1998).The molecular mass of CD36 on different cells is variable; for example, M r values of 88 000, 85 000 and 78 000 have been reported for human platelets, human mammary epithelial cells, and human erythroblasts, respectively (Tandon et al, 1989b;Greenwalt et al, 1990;Kieffer et al, 1989).A cDNA clone encoding CD36 was isolated from a human placenta cDNA library and expressed in COS cells by Oquendo et al (1989), resulting in a polypeptide with 471 residues and a predicted M r of approximately 53 kD. The identification of 10 potential N-linked glycosylation sites accounted for the difference in M r between the polypeptide and the 83 kD species found by immunoprecipitation with a pool of mouse monoclonal anti-CD36 antibodies. Tandon et al (1989b) purified CD36 from solubilized Triton X-114 extracts of human platelet membranes, and report...

Expression of Human Scavenger Receptor B1 on and in Human Platelets

“…10,28 Several studies have confirmed the possible importance of anti-CD36 antibodies in various thrombotic disorders, including thrombotic thrombocytopenic purpura and idiopathic thrombocytopenic purpura. 29,30 The above discussion relates hSR-B1/CLA-1 expression to cholesterol metabolism but does not address the changes in platelet aggregation. Our interest in this parameter led us to use laser light scattering, a technique for measuring changes in ability of the platelets to aggregate.…”

Complete deficiency in ADAMTS13 is prothrombotic, but it alone is not sufficient to cause thrombotic thrombocytopenic purpura

“…In the present study, we observed enhanced thrombus formation on collagen surface under flow and promoted thrombocytopenia induced by the injection of a mixture of collagen and epinephrine in ADAMTS13-deficient mice. Genetic defects or environmental factors may stimulate endothelial activation or damage via TTP triggers, such as oxidative stress, 33 infection, 34 antiendothelial cell antibodies, 35 or complement dysfunction. 36,37 ADAMTS13-deficient mice may be useful to identify TTP triggers.…”

Decreased von Willebrand factor protease activity associated with thrombocytopenic disorders

“…12,21 A number of hypotheses have been put forward to explain the platelet thrombi that characterize TTP. These include an abnormal apoptotic factor, 22,23 a variety of platelet aggregating factors, [24][25][26][27] and abnormalities of vWF. [7][8][9][10][11][12][13][14][15][16][17][18][19][20] Our group has postulated that a Figure 2.…”