In Focus
Platelet Immunobiology Working Party
What you need to know about the Working Party and its activities
Brian Curtis
Platelet & Neutrophil Immunology Lab Versiti Blood Center of Wisconsin Milwaukee, USA Read bio >
The aim of the Platelet Immunobiology Working Party (PIWP) is to enable collaborations in platelet immunology by bringing together members working in a diagnostic, research and/or clinical laboratory setting.
The Platelet Immunology Working Party (PIWP) currently supports 31 lab members representing 20 different countries on 5 continents (Figure 1).
Figure 1. Platelet laboratories supported by the Working Party
Platelet Immunology involves study of the pathogenic immune mechanisms responsible for platelet disorders related to alloantibodies or autoantibodies against platelets. Platelet disorders caused by antibodies against platelets include immune thrombocytopenia (ITP), fetal & neonatal alloimmune thrombocytopenia (FNAIT), drug-induced immune thrombocytopenia, and platelet-transfusion refractoriness. Please see the specific articles in this edition of In Focus that describe each of these disorders in more detail. Rapid and precise diagnosis of these disorders using reliable platelet serologic testing and typing for human platelet antigens (HPA) is mandatory to avoid severe clinical consequences for patients. Understanding the underlying mechanisms is a key to better diagnosis, treatments, and prophylaxis.
Scope of the Working party
We bring together like-minded colleagues with interests in all aspects of platelet immunology with the primary goal to improve diagnostic laboratory testing for the detection and identification of platelet antibodies and antigens.
Human Platelet Antigens
The PIWP is also responsible for establishing and monitoring the nomenclature for human platelet antigens (HPA). There are currently 41 HPA expressed on 6 different platelet membrane glycoproteins GPIIb/CD41, GPIIIa/CD61, GPIbα/CD42b, GPIX/CD42a, GPIa/CD49b, and CD1091. All are biallelic single nucleotide variants (SNV) in genes that encode the aforementioned major platelet glycoproteins. The antigens are numbered in their order of discovery, and the higher frequency antigen is designated “a” and the lower frequency antigen “b”, (e.g., HPA-1a and HPA-1b). When an investigator has discovered what they believe is a “new” HPA, they submit their evidence to the PIWP where it is reviewed, and if confirmed to be accurate, the PIWP assigns it the next HPA number. Antibodies that react against non-HPA on platelets are also important. Some of these include, class I HLA antibodies, ABO blood group antibodies, iso-antibodies against CD36/GPIV (see related article), GPIb/IX, and GPIIb/IIIa, and drug-dependent antibodies (see specific articles).
Tests for Platelet Antigens and Antibodies
Patients affected with immune platelet disorders can make antibodies against platelet antigens when they are immunized by pregnancy or transfusions. Reference labs like those represented by PIWP members perform specialized testing to detect platelet antibodies and antigens and combine the results with their expertise to help physicians make a patient’s diagnosis. We encourage and support new and emerging platelet immunology laboratories through education and organisation of practical biennial international workshop sessions (see In Focus article - PIWP International Platelet Immunology Workshop) where we exchange between members testing reagents, controls, and test protocols. These exercises are designed to improve laboratory testing for platelet antibodies and antigens. We hope you enjoy learning about Platelet Immunology and the important work of the PIWP. If you have questions or are interested in joining the PIWP, you can find more information here.
