Ahmad Sarfraz, Bacher H Peter, Lassen Michael R, Hoppensteadt Debra A, Leitz Helen, Misselwitz Frank, Walenga Jeanine M, Fareed Jawed
Loyola University of Chicago, Stritch School of Medicine, Maywood, Ill, USA.
Arch Pathol Lab Med. 2003 May;127(5):584-8. doi: 10.5858/2003-127-0584-IOTIST.
It is now widely accepted that the pathophysiology of heparin-induced thrombocytopenia (HIT) syndrome is mediated by the generation of a wide array of functional and molecularly heterogeneous anti-heparin-platelet factor 4 (AHPF4) antibodies that may mediate platelet and/or endothelial cell activation/destruction.
We investigated the differential prevalence and functionality of AHPF4 immunoglobulin subtypes (IgA, IgG, and IgM) in plasmas obtained from orthopedic patients immobilized with Plaster-Cast and treated with clivarin (a low-molecular-weight heparin) in comparison to a placebo for the prophylaxis of deep-vein thrombosis.
Clivarin was administered subcutaneously at a fixed daily dosage of 1750 U without any adjustment or loading dosage. Citrated plasmas were obtained at baseline, at 10 to 14 days, and at postbrace procedure (5-12 weeks). An enzyme-linked immunosorbent assay (ELISA) was used to quantitate the AHPF4 antibody titers. The functionality of the ELISA-positive samples was determined by a 14C-serotonin release assay (SRA).
In the ELISA test, 16 of 1073 samples (1.5%; 6 in clivarin and 10 in placebo groups) were positive for AHPF4 antibodies (mean optical density [OD] = 0.46 +/- 0.02). None of the ELISA-positive samples for AHPF4 antibodies could mediate platelet activation responses as determined by the SRA (0%-3% serotonin release, P >.10, n = 16). Through differential immunoglobulin subtype analysis of the samples positive for (cumulative) AHPF4 antibodies, we determined that their relative prevalence in plasma were as follows: IgM (mean OD = 0.71 +/- 0.13) > IgG (0.31 +/- 0.08) > IgA (0.14 +/- 0.02). Although there was no significant difference in the total antibody titers between clivarin and placebo groups, the antibody subtyping data showed conversion trends (ie, IgA [clivarin to placebo], IgG [placebo to clivarin], and IgM [clivarin to placebo]).
These observations indicate that even at reduced dosages, clivarin can shift the immunogenic up-regulation toward the IgG subpopulation; however, the IgG subtype is of a nonfunctional type of AHPF4 antibody and thus may not cause any HIT-related pathogenic responses.
目前广泛认为，肝素诱导的血小板减少症（HIT）综合征的病理生理学是由多种功能和分子异质性的抗肝素血小板因子4（AHPF4）抗体介导的，这些抗体可能介导血小板和/或内皮细胞的激活/破坏。
我们研究了与用于预防深静脉血栓形成的安慰剂相比，在使用石膏固定并接受克立肝素（一种低分子量肝素）治疗的骨科患者血浆中，AHPF4免疫球蛋白亚型（IgA、IgG和IgM）的差异患病率和功能。
克立肝素以每日1750 U的固定剂量皮下给药，无需调整或负荷剂量。在基线、10至14天以及去除石膏后（5 - 12周）采集枸橼酸化血浆。采用酶联免疫吸附测定（ELISA）定量AHPF4抗体滴度。ELISA阳性样本的功能通过14C - 5羟色胺释放试验（SRA）测定。
在ELISA试验中，1073份样本中有16份（1.5%；克立肝素组6份，安慰剂组10份）AHPF4抗体呈阳性（平均光密度[OD] = 0.46 ± 0.02）。如SRA所测定，AHPF4抗体的ELISA阳性样本均不能介导血小板激活反应（5羟色胺释放0% - 3%，P > 0.10，n = 16）。通过对（累积）AHPF4抗体阳性样本进行免疫球蛋白亚型差异分析，我们确定它们在血浆中的相对患病率如下：IgM（平均OD = 0.71 ± 0.13）> IgG（0.31 ± 0.08）> IgA（0.14 ± 0.02）。尽管克立肝素组和安慰剂组之间的总抗体滴度无显著差异，但抗体亚型分析数据显示了转换趋势（即IgA[克立肝素组到安慰剂组]、IgG[安慰剂组到克立肝素组]和IgM[克立肝素组到安慰剂组]）。
这些观察结果表明，即使在降低剂量时，克立肝素也可使免疫原性上调转向IgG亚群；然而，IgG亚型是一种无功能的AHPF4抗体类型，因此可能不会引起任何与HIT相关的致病反应。
