Untch Brian, Ahmad Sarfraz, Jeske Walter P, Messmore Harry L, Hoppensteadt Debra A, Walenga Jeanine M, Lietz Helen, Fareed Jawed
Department of Pathology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL 60153, USA.
Thromb Res. 2002 Jan 15;105(2):117-23. doi: 10.1016/s0049-3848(02)00004-x.
Antibodies to heparin-platelet factor 4 (PF4) complexes have been observed in patient with heparin-induced thrombocytopenia (HIT) syndrome. These antibodies may be of various isotypes and differ with respect to their ability to activate platelets/endothelial cells. This study determined the isotypes and functionality of antiheparin-platelet factor 4 (AHPF4) antibodies in 111 patients treated with heparin and clinically suspected for HIT. In this patient population, 50% had detectable AHPF4 cumulative IgA, IgG, and IgM (determined by enzyme-linked immunosorbent assay, ELISA), but only 35% was positive when tested with the (14)C-serotonin release assay (SRA). Using antihuman Ig specific for different isotypes, we found that 50% of the 111 samples was positive for IgG, 45% for IgM, and 37% for IgA. In 50 normal human serum (NHS) samples, only two were positive for IgG, but 33 were positive for IgM, indicating a potential humoral response to the heparin-PF4 complex prior to heparin administration. Patients that were ELISA(+) for AHPF4 antibody titer were subdivided into SRA-positive (+) and SRA-negative (-) groups. The SRA(+) group had a mean ELISA optical density (OD) for AHPF4 IgA/IgG/IgM of 2.1, while the SRA(-) group had a mean OD of 0.8 (P<.001). The SRA(+) group had greater mean OD values for all three individual isotypes. Using flow cytometry, we determined the ability of different patient samples to activate platelets. Samples that contained IgG and were SRA(+) activated platelets (as measured by microparticle generation and P-selectin expression) in the presence of therapeutic concentrations of heparin. NHS and samples containing IgA and/or IgM that were SRA(-) were not able to produce microparticles nor were they able to increase expression of P-selectin. Together, these data indicate that IgG is the principal mediator of platelet activation in patients with HIT, with IgA and IgM playing a less significant role in the pathophysiology of this syndrome.
在肝素诱导的血小板减少症（HIT）综合征患者中已观察到针对肝素 - 血小板因子4（PF4）复合物的抗体。这些抗体可能具有多种亚型，并且在激活血小板/内皮细胞的能力方面存在差异。本研究确定了111例接受肝素治疗且临床怀疑患有HIT的患者中抗肝素 - 血小板因子4（AHPF4）抗体的亚型和功能。在该患者群体中，50%的患者可检测到AHPF4累积IgA、IgG和IgM（通过酶联免疫吸附测定法，即ELISA测定），但用（14）C - 血清素释放试验（SRA）检测时，只有35%呈阳性。使用针对不同亚型的抗人Ig，我们发现111份样本中有50%的IgG呈阳性，45%的IgM呈阳性，37%的IgA呈阳性。在50份正常人血清（NHS）样本中，只有两份IgG呈阳性，但33份IgM呈阳性，这表明在给予肝素之前可能对肝素 - PF4复合物存在体液反应。将AHPF4抗体滴度ELISA呈阳性（+）的患者分为SRA阳性（+）组和SRA阴性（ - ）组。SRA（+）组AHPF4 IgA/IgG/IgM的平均ELISA光密度（OD）为2.1，而SRA（ - ）组的平均OD为0.8（P<0.001）。SRA（+）组所有三种个体亚型的平均OD值更高。使用流式细胞术，我们确定了不同患者样本激活血小板的能力。含有IgG且SRA（+）的样本在治疗浓度的肝素存在下激活血小板（通过微粒生成和P - 选择素表达来衡量）。NHS以及含有IgA和/或IgM且SRA（ - ）的样本既不能产生微粒也不能增加P - 选择素的表达。总之，这些数据表明IgG是HIT患者血小板激活的主要介质，而IgA和IgM在该综合征的病理生理学中起的作用较小。
