臺灣地區分離式捐血人血小板CD36表現缺乏、相關基因變異調查及其對血小板血品品質影響之研究

Abstract

中文摘要 CD36為一種血小板上的特異性抗原，又稱 glycoprotein IV(GP IV)。過去文獻報告關於台灣地區血小板CD36缺乏的頻率約為1.6%~4%間。CD36缺乏有兩種型態：第一型CD36缺乏為血小板和單核球上都偵測不到CD36；第二型CD36缺乏只有血小板上偵測不到CD363，至今陸續有關於CD36缺乏和可能的基因變異的研究發表。CD36抗原缺乏受血者若因異體免疫產生anti-CD36抗體，除了會導致血小板輸注無效，輸血後紫斑，各種免疫性血小板減少等臨床症狀；也有研究指出CD36缺乏與高血脂症有關聯4。近來CD36基因剔除的小鼠研究發現，血小板可經由CD36接受微顆粒(microparticles)的刺激而活化，CD36缺乏血小板被微顆粒活化的能力會降低，因而使止血時間延長。 本研究旨在調查台灣地區血小板分離術捐血人其血小板和單核球上CD36的表現，並區分出第一型和第二型的CD36缺乏，以預估國人因CD36抗原缺乏導致輸血後輸注無效的風險機率，並探討引起CD36缺乏可能的基因變異、以及CD36缺乏對血小板血品品質的影響。共募集640位健康的分離術血小板捐血人，檢測其CD36結果，在國人發生血小板完全缺乏（CD36 deficiency）之比率為1.6%，屬第一型CD36缺乏者有4人（0.6%）、第二型CD36缺乏有6人（1%）。血小板上CD36表現低於一般分佈之25%者定義為CD36 reduced (CD36 低下)共160人。分析國人CD36基因序列，在CD36缺乏/低下受試個案發現與CD36缺乏/低下有關的變異有1163A>T、1200-5 49bp inv、1254+6 del TATTTG等。檢測並比較CD36缺乏/低下受試個案與對照組間全血及所捐血小板濃厚液血品止血功能差異，以及查詢曾有因脂血而無法捐血之記錄，得到以下結論：1、國人血小板CD36缺乏的發生率為1.6%，CD36基因變異種類與國外常見之268 C>T和975 T>G變異型不同。掌握慣常血小板分離術捐血人中CD36缺乏者名單，對於因異體免疫產生anti-CD36抗體而合併血小板輸注無效的受血者，則可輸注特定CD36缺乏捐血人所捐之的血品，以提升輸血效果。2、血小板CD36缺乏捐血人臨床上並無止血異常情形，雖然其全血TEG檢測凝血功能各項參數與血小板CD36正常表現者有顯著差異，但仍屬正常參考範圍。3、CD36缺乏的分離術收集之血小板濃厚液血品在第五天末效時，和CD36正常血品比起來雖然TEG檢驗各項參數與CD36正常血小板有差異，但均在正常範圍內，其血品止血的品質應是可接受的。4、血小板CD36缺乏和低下之捐血人較正常人產生脂血的機會較高(p<0.0001)，所以需加強宣導其捐血前飲食的控制。

CD36, also known as platelet (PLT) glycoprotein IV (GPIV), is a class B scavenger receptor on platelets. Previously, prevalence of PLT CD36-deficiency in Taiwanese was reported to be 1.6-4%. There are two types of CD36 deficeincy. Type I CD36-deficiency was characterized as CD36 deficiency on both monocytes and platelets, while in type II CD36-deficiency, CD36 is expressed on monocytes but not on PLTs. Study on CD36 deficiency with possible CD36 genetic variations has been published in the past few years. CD36 deficiency subjects might be immunized by transfusion and induce anti-CD36 antibody, which could result in platelet transfusion refractoriness, post-transfusion purpura, and other types of immune-related thrombocytopenia. Moreover; studies also pointed out that CD36 deficinecy was associated with hyperlipidemia. Studies in CD36 knockout mice revealed that microparticles could stimulate platelets activation through CD36. Platelets with CD36 deficinecy will reduce platelet interaction with microparticles, and resulted in prolongation of bleeding time. The aims of this study are 1) to clarify the expression of CD36 on monocytes and platelets from apheresis donors in Taiwan and classified CD36-deficient Taiwanese subjects into types I and II, and 2) to study the CD36 genetic variations in each subject and their relation to CD36 deficiency, 3) to investigate the possible effect of CD36 deficiency on the quality of platelet components. A total of 640 apheresis donors were recruited in this study. Type I and type II deficiency were found in 4 (0.6%) and 6 (1%) of the donors, respectively. One hundred and sixty donors (25%) were found to have reduced expression of CD36 on their platelets. In molecular analysis of the coding sequence of CD36 gene in subjects with deficiency/reduced PLT CD36, we found three previously un-published variations: 1163A>T、1200-5 49bp inv and 1254+6 del TATTTG. Coagulation of whole blood as well as the platelet concentrate was assessed to see if CD36 deficiency would cause delayed hemostasis. Records of lipemia-related events in blood donation were inspected. The results indicated that: 1. the incidence of CD36 deficiency in Taiwanese is 1.6%. The genetic variations of CD36 gene identified in Taiwanese CD36 deficient subjects are differed from those reported in Japanese and Africans. The database of the Taiwanese CD36-deficient apheresis donors may be useful in the future for providing platelets for patients with CD36 iso-immunized. 2. Apheresis donors with CD36 deficiency do not show abnormal whole blood Thrombelastograph (TEG) coagulation test. Although the results of whole blood TEG test in CD36-deficient donors were significantly different from that of the controls, that they were still within normal range. 3. After 5 days of storage, the platelet TEG test results of components prepared from CD36 deficienct subjects were significantly different from that of the controls, but still fall within normal range. The platelet function of platelet components prepared from CD36 deficient donors is acceptable. 4. The donors with deficient/reduced platelet CD36 have higher chance of lipemia than the CD36 normal donors (p<0.0001), so health education should be stressed in these donors to reduced the possibility of hyperlipidemia-associated problems in blood donation.