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Background and Objectives

  1. Top of page
  2. Background and Objectives
  3. Aims
  4. Methods
  5. Discussion/Conclusions
  6. Disclosure

HPA antibodies (Abs) are involved in the pathogenesis of thrombocytopenia, including neonatal alloimmune thrombocytopenia (NAIT), platelet transfusion refractoriness (PTR) and post transfusion purpura (PTP). The detection and identification of causative HPA Abs is essential, but sometimes not possible, for the correct diagnosis and the implementation of the appropriate treatment.

There are several useful methods for the detection of HPA Abs, such as monoclonal antibody immobilization of platelet antigens (MAIPA), mixed passive haemagglutination (MPHA) assay, platelet immunofluorescence test (PIFT), modified antigen capture ELISA (MACE) and solid phase red cell adherence (SPAA). Each method has its advantages as well as disadvantages. In our experience, MAIPA is able to identify the HPA antibodies in sera containing multiple specificities or HLA antibodies, but the procedure is quite complex, which is an obstacle for the screening of a large number of samples. On the other hand, MPHA is a few-stepped, simple method, allowing analysis of large cohort of samples in a single microtitre plate, but some expertise is needed for the judgment of the results, and frequently the detection of HPA antibodies is interfered by the presence of a concomitant HLA antibody. This problem can be overcome by removal of platelet HLA using chloroquine, however this treatment also impairs other platelet antigenicity. MAIPA is a largely applied method in Europe and US, whereas MPHA is widely used in Japan and some Asian countries.

Aims

  1. Top of page
  2. Background and Objectives
  3. Aims
  4. Methods
  5. Discussion/Conclusions
  6. Disclosure

Although several useful methods are available for the detection of HPA Abs, no one technique alone is able to detect all the clinical significant antibodies in platelet immunology. Thus, there is need to improve the presently available methodologies, as well as to combine them to establish the best system for HPA antibody detection. The HPA antigen frequencies vary significantly among populations. For example, the HPA-1 system has important clinical implications among Caucasian, but not among Asian. On the other hand, antibodies against HPA-4 and GPIV are clinically relevant in Japan and some Asian countries, but irrelevant in Caucasian. Through the activities of the International Platelet Immunology Working Party (IPIWP), the platelet immunology field has progressed tremendously, and labs from most European countries, United States and Japan had shared knowledge and improved the skills by participating of the biannual workshops. In 2008, Dr. Guo-Guang Wu, one of the members of the organizing committee of this Asian WP, organized the 14th ISBT Platelet Immunology Workshop during the International Meeting of ISBT in Macao. Most labs from Asian countries, however, were not able to actively attend this WP, most probably caused by the shortage of skills, expertise and funding.

Dependent on the unavailability of adequate methodology and the different antigenic frequencies, clinically relevant new HPA antibodies may be overlooked in Asian population. Therefore, there is need to develop a strong working network among laboratories in Asian countries to improve the platelet immunology field in this region. For this purpose, we proposed to establish the Asian Platelet Immunology Working Party (APIWP), as part of the International Platelet Workshop of the ISBT (IPIWP), in which Asian labs as well as other interested labs can collaborate to implement in their methodologies, through the provision and exchange of materials and protocols, testing their skills through serological and molecular biological exercises, discuss the problems and find the solutions within the framework of biannual meetings of the Regional Congress of ISBT in Asia.

Methods

  1. Top of page
  2. Background and Objectives
  3. Aims
  4. Methods
  5. Discussion/Conclusions
  6. Disclosure

The first proposal of the Asian Platelet Immunology Working Party (APIWP) was presented during the International Platelet Immunology Working Party (IPIWP) of ISBT in Berlin (2010). The Chairperson of the APIWP is Dr. Cecile Kaplan-Gouet (Chairperson of the IPIWP). The organization committee is composed by Dr. Guo-Guang Wu, Nanning Institute of Transfusion Medicine, China, Prof. Kyou Sup Han, Department of Laboratory Medicine, Seoul National University Hospital, South Korea, and me. Dr. Nelson H. Tsuno, from my department, is responsible for the general management of the APIWP. Dr. Sentot Santoso, Institute for Clinical Immunology and Transfusion Medicine, Justus Liebig University acts as the Advisor of the APIWP.

A questionnaire was sent to the potential participants of the APIWP, and among the 22 labs, 14 labs, 5 from Japan, 3 from China, 1 from South Korea, 1 from Taiwan, 1 from Philippines, 1 from Thailand, 1 from Indonesia, and 1 from Malaysia, revealed interest to participate. In all 5Japanese labs MPHA and MAIPA are available for platelet antigen/antibody serological testing, while in other Asian labs, MPHA is used only in two labs and MAIPA is performed in three labs. These potential participant Asian labs were invited for a training program in platelet immunology methods, organized in collaboration with Dr. Santoso, and took place in my department at the University of Tokyo, in November, 2010. Seven people from 5 countries attended, and the course was very successful. All attendee gained hands-on experience in the MAIPA, MPHA and PIFT methods, and were very enthusiastic to participate on the workshop.

After the training course, the first Workshop of the APIWP which consist of exercises on platelet serology and genotyping, followed by a meeting during the Regional Congress of ISBT in Taipei, November 20, 2011, was announced. All the 14 labs revealed interest to participate. Materials for the exercises, consisting of six serum samples, six DNA samples, as well as monoclonal antibodies for MAIPA and the kits of MPHA, as well as the protocols, were distributed to the labs in June 2011. Since the sensitivity and specificity of the indicator sheep red cells coated with anti-human IgG for MPHA is absolutely required, we sent the qualified indicator sheep red cells coated with anti-human IgG. The kits of MPHA also contained microtitre plates coated with platelets extracts to detect HPA and HLA antibodies for screening or for determination as well as chloroquine solution. The general aim of this exercise will be to confirm the skills and the performance of each lab related to platelet serology and genotyping, in an attempt to determine the problems and needs, which should be discussed and solved in the future meetings.

All labs received the materials in good conditions, and have about 3 months to finalize the exercise. The results will be collected in September 2011, analysed thereafter, and will be presented in November 20, 2011, in Taipei during the ISBT meeting, organized by Dr. Chen-Chung Chu, from Mackay Memorial Hospital, Taiwan.

Discussion/Conclusions

  1. Top of page
  2. Background and Objectives
  3. Aims
  4. Methods
  5. Discussion/Conclusions
  6. Disclosure

The APIWP was established in an attempt to implement and develop the platelet immunology field in Asia as well as other interested countries. Considering the different frequency of HPA between Caucasian and Asian populations, there is the possibility that new and relevant platelet antibodies are overlooked, and this Working Party will enormously contribute for the development of this field. We hope further many active international colleagues will join APIWP and finally we would like to establish international practical standard methods for detection of platelets alloantibodies compiled by the WS.

This WP was established under strong support of Dr. Silvano Wendel, the President of the ISBT, Dr. Cecile Kaplan-Gouet, the Chairperson of the IPIWP, and was approved by the members of the IPIWP. Dr. Sentot Santoso is giving us a strong support for the implementation of the workshop. The organization committee of the APIWP would like to take this chance to thank all who collaborate for the establishment of the APIWP.

Disclosure

  1. Top of page
  2. Background and Objectives
  3. Aims
  4. Methods
  5. Discussion/Conclusions
  6. Disclosure

No potential conflict of interests to declare.