Test erythrocytes

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In immunohematology and transfusion medicine, test erythrocytes are those red blood cells ( erythrocytes ) that are used in the laboratory as detectors, in vitro , for antibodies in particular to be identified and unknown . The antigen-antibody reaction is central, because if the test erythrocytes carry the antigen on their surface, agglutination with corresponding anti-erythrocyte antibodies from the patient's serum occurs . Immunohematologically relevant erythrocyte antigens are located as molecular structures on the erythrocyte membrane.

Human test erythrocytes are obtained from blood donors and produced in industrial processes. The test erythrocytes are sold as a three to five percent erythrocyte suspension ( Alsever's solution ). The test erythrocyte solutions must not be mixed together.

Erythrocyte antigens are genetically determined, immunogenic features of the erythrocyte cell membrane that are grouped into different antigen systems depending on structure and function. Up to 2004, more than 600 erythrocyte antigens had been serologically defined; they are listed in the constantly updated nomenclature of the International Society of Blood Transfusion (ISBT) in 29 blood group antigen systems. Antibodies are formed against some of these erythrocyte antigens, either as irregular erythrocyte antibodies, which were acquired, for example, through pregnancy or blood transfusion, or as regular erythrocyte antibodies. Such antibodies can be detected by the test erythrocytes.

Since some erythrocyte antigens are very unevenly distributed in the human population ( common antigens and private antigens ), donors are required for the antibody search test with test erythrocytes, as they are extremely rare. Some transfusion medicine institutes usually have their own collection of rare, cryopreserved test erythrocytes. In Germany, the working group "Rare Blood Groups of the German Society for Transfusion Medicine and Immunohematology (DGTI)" deals with this topic.

Using the test erythrocytes

If test erythrocytes are used for the serum cross-check (isoagglutinins) in the ABO blood group determination, test erythrocytes of groups A 1 , B and 0 are used. The approach with test erythrocytes of group A 2 is optional.

Human test erythrocytes are required to carry out an antibody screening as part of the blood group determination in the serum of the patient to be examined , for the serum cross-check and the like. a. m. The antibody screening test is used to detect irregular (non-natural) antibodies in the patient's serum against erythrocyte antigens. This is because irregular antibodies are antibodies which (in contrast to isoagglutinins or blood group antigens ) were formed by unnatural sensitization (e.g. through blood transfusions , pregnancy). For the antibody screening test, test erythrocytes are used, which should have the following antigens:

An antibody screening test may be carried out with one or more test pools. However, a maximum of two different test cells may be present in a test pool. The antigens C, c, E, e, Fya, Fyb, Jka, Jkb, S and s must be "homozygous" in at least one cell. Commercial test erythrocytes used for the antibody screening test must be negative for the antigens M g , Wr a and Vw.

Was in the antibody screening an erythrocyte antigen in the serum of patients found to need an antibody differentiation follow. Although the antibody differentiation is carried out in a similar way to the antibody screening test, not only two or three test erythrocytes with known antigens are used, but twelve or more different test erythrocytes are used. Such a test cell combination is also called a “test panel”. Depending on the erythrocytes with which (hem) agglutination occurs, the specificity of the antibody can then be concluded. Test erythrocytes loaded with human IgG immunoglobulins are used to control the anti - human globulin serum (“ Coombs control ”).

literature

  • Volker Kiefel, Christian Müller-Eckhardt (ed.): Transfusion medicine and immunohematology: Basics - Therapy - Methodology. Springer, Berlin / Heidelberg / New York 2010, ISBN 3-642-12764-9 , p. 79 f
  • Reinhold Eckstein, Robert Zimmermann: Immunohematology and clinical transfusion medicine: theory and practice compact paperback. Edition 7, Urban & Fischer Verlag / Elsevier, Munich 2015, ISBN 3-437-31681-8 , p. 13
  • Nicola Adam: Anti-erythrocytic alloimmunization as a complication of hemotherapy. A retrospective evaluation of the hemovigilance data from the University Hospital Münster. Dissertation, Westfälische Wilhelms-Universität Münster 2008 [4]
  • Norbert Ahrens: Mechanisms of immunization against erythrocyte antigens. Habilitation thesis, Medical Faculty Charité, Universitätsmedizin Berlin 2009 [5]
  • Diether Schönitzer: DNA-based blood grouping - the end of serology? The combination of both techniques - DNA analysis and classic serology - would be ideal. science & practice, pp. 14–16 [6]

Web links

  • Antisueros. EL COMPLEMENTO ideal. from grifols .com [7]
  • IMMUNHEMATOLOGY from DiaMed [8]
  • Antibody Detection and Identification. LabCE [9]
  • Lecture on transfusion medicine. Antibody differentiation. Immunohematological laboratory analysis [10] and lecture on transfusion medicine at the Institute for Clinical Transfusion Medicine and Haemotherapy at the University of Würzburg [11]
  • Evaluation chart for a test panel with ten test erythrocytes [12]

Individual evidence

  1. ↑ Alsever's solution. BAG Health Care GmbH [1]
  2. ↑ International Society of Blood Transfusion (ISBT) [2]
  3. ↑ Working group on rare blood groups. German Rare Donor Program [3]