What are anti-M antibodies

Erythrocyte Laboratory

In the erythrocyte laboratory, special tests are carried out to diagnose immunohematological symptoms of red blood cells (such as autoimmune hemolytic or drug-induced anemias), to differentiate between alloantibodies against erythrocytes and to detect blood group characteristics (including molecular genetic determinations). You can find our form for sending in blood samples from external patients here.


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Marburg: Transfusion Medicine / Blood Bank, Baldingerstraße, 35043 Marburg
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Laboratory management

Miss Dr. Flommersfeld
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Updated on:20.11.2018


 

Erythrocyte Immunology

Determination of the rhesus formula and other blood group antigens
The determination of the Rhesus characteristics C, c, E, e and other blood group characteristics (Cw, K, k, Kpa, Kpb, Fya, Fyb, Jka, Jkb, M, N, S, s, Lea, Leb, Lua, Lub, P1 ) is carried out with two different test reagents.
AnalyteAntigens on red blood cells
indicationThe Rh traits C, c, E, e and the K trait are determined for all blood donors and blood recipients. After antibody differentiation, antigenic tests should clarify whether allo- or autoantibodies are present.
material10 ml EDTA blood
methodAgglutination test
Reference rangenot applicable
ratingAs a rule, antibodies that are identified in the antibody differentiation are alloantibodies: the patient does not have the antigen against which antibodies are formed, the antigenic test is negative. Exceptions can be made for anti-M, -N, -e, and in rare cases -D.
Pretransfusions of erythrocytes with different antigen patterns can make the evaluation of the antigen determination difficult or impossible.
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Antibody screening test
The antibody search test detects clinically relevant erythrocytic allo- and autoantibodies outside the
AB0 blood group system. It is part of the determination of blood groups in patients and blood donors.
Analytefree antibodies against erythrocytes
indicationThe antibody screening test is carried out with a serological tolerance test if the last previous antibody screening test was more than 3 days ago. For blood donors, an antibody screening test is carried out at least every two years and after transfusions and pregnancies. In addition, an antibody search test is carried out on Rh-negative women in the antenatal diagnosis.
material10 ml EDTA blood
methodAgglutination test (including indirect antiglobulin test or IgG-specific test [solid phase])
Reference rangenegative
ratingIf free, irregular erythrocyte antibodies are present, at least one of the 2 - 3 test erythrocytes will react positively. The specificity of detected antibodies is identified by means of antibody differentiation. To detect cold antibodies and antibodies of certain specificities, the antibody search test can also be carried out in different environments (NaCl, bromeline, etc.) and at different temperatures.
Differential diagnosesIf the antibody search test is positive, the following may be present:
- Erythrocyte alloantibodies when immunized against foreign blood group characteristics after blood transfusions or after pregnancy
- Red cell autoantibodies in autoimmune hemolysis
- Currently after rhesus prophylaxis during pregnancy
- Transfer of maternal antibodies into the child's circulation in newborns
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Serological tolerance test (cross match)
The cross match records clinically relevant blood group serological incompatibilities between donor and recipient. In contrast to the antibody search test, it can also be used to detect AB0 incompatibility and antibodies against private erythrocyte antigens. It is carried out as a major test in the indirect antiglobulin test.
Analytefree antibodies against erythrocytes
indicationBefore red cell transfusions
material10 ml EDTA blood (recipient)
methodAgglutination test (including indirect antiglobulin test or IgG-specific test [solid phase])
Reference rangenegative
ratingIn the event of a positive cross match, the following may be present
- AB0 incompatibility
- Allo- or autoantibodies (see antibody screening test)
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Antibody identification (antibody differentiation)
The specificity of antibodies in the serum is determined by testing the serum against a large number of test erythrocytes (panel cells) which have all the essential erythrocyte antigens in a known distribution.
Analytefree antibodies against erythrocytes
indicationPositive antibody screening test
material10 ml EDTA blood
methodAgglutination test (including indirect antiglobulin test in various environments, adsorption and elution processes (acid, heat, chloroform) + [solid phase])
Reference rangenegative
ratingThe antibody specificities can be determined on the basis of the reaction pattern of the panel cells. Homogeneous reactions of all panel cells can be caused by autoantibodies (own preparation positive) or very broadly reacting alloantibodies (own preparation negative).
In the case of multiple antibodies of different specificities or combined presence of auto and alloantibodies, further tests may be necessary to clarify the specificity (other panel cells, adsorption, elution, etc.).
To detect cold antibodies and to clarify the specificity of certain antibodies, antibody differentiation can also be carried out in different environments (NaCl, bromeline, etc.) at different temperatures.
Differential diagnosessee antibody screening test
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Antibody titration
To estimate the concentration of erythrocyte antibodies, the reaction strength of a geometric dilution series of the patient's serum with test erythrocytes is determined.
Analytefree antibodies against erythrocytes
indication- Controls during pregnancy to assess the risk of M. haemolyticus neonatorum
- Progressive titration of autoantibodies
- Determination of isoagglutinin titers in AB0-incompatible live kidney transplantation and heart transplantation
- Detection of weak blood group antigens by adsorption and subsequent titration of corresponding antibodies
material10 ml EDTA blood
methodAgglutination test (indirect antiglobulin test)
Reference rangedepending on the question
ratingDue to the changing antigenicity of the test erythrocytes used and manual pipetting, only a titer difference of at least two titer levels can be regarded as significant when observing the progress. It is advisable to carry patient sera from preliminary examinations with you for control purposes.
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Direct antiglobulin test
Antiglobulin sera of various specificities agglutinate erythrocytes which are loaded with corresponding immunoglobulins (IgG, IgM, IgA) or complement factors (C3d, C3c).
Analyteimmunoglobulins bound to erythrocytes and complement factors
indication- Clarification of transfusion reactions
- V. a. Autoimmune hemolysis
- V. a. Haemolyticus neonatorum disease
- V. a. Drug-induced immune hemolysis
material10 ml EDTA blood
methodAgglutination test
Reference rangenegative
ratingDepending on the underlying disease (see indications), there are different reaction patterns of the various antiglobulin sera.
Differential diagnosesOther possible causes of a direct antiglobulin test are:
- Rhesus prophylaxis for the mother (in newborns)
- heat autoantibodies without hemolytic activity
- unspecific immunoglobulin load
- In vitro complement activation by cold autoantibodies
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Autoimmune Hemolytic Anemia (AIHA) of the caloric type
The incidence of AIHA is estimated at 1: 40,000 to 1: 80,000, of which about 70% are of the heat type. The idiopathic form occurs more frequently in women and over the age of 40. The secondary AIHA of the heat type can occur in underlying diseases such as tumors (especially lymphomas, ovarian teratomas), myeloproliferative diseases, immunodeficiencies and autoimmune diseases. Clinical and laboratory hemolysis signs are found in the patients. Therapy is carried out with corticosteroids and immunosuppressive cytostatics. Transfusions are indicated if the clinical situation is appropriate (anemia).
AnalyteAutoantibodies against erythrocytes
indicationV. a. Autoimmune hemolysis
material10 ml EDTA blood
methodDirect and indirect anti-human globulin test (antibody search test and differentiation), elution method
Reference rangenegative
ratingThe main finding is the direct Coomb test positive with anti-IgG. In 60% of the cases he is also positive with anti-C3d. In rare cases, heat autoantibodies of the IgA and IgM class are present, which in very rare cases are the sole cause of AIHA.
After elution, broadly reacting antibodies with no recognizable specificity can be detected. In very rare cases the direct antiglobulin test is negative and heat autoantibodies can only be detected after elution. If an AIHA is present, regular check-ups and monitoring of the hemolysis parameters are indicated.
Differential diagnoses- Other forms of autoimmune hemolysis
- Haemolytic transfusion reactions
- EMH
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Cold agglutinin disease (cold-type AIHA)
Chronic cold agglutinin disease can occur idiopathically in patients over the age of 50 or secondarily as a result of malignant diseases, mostly B-cell lymphomas. The main symptoms are acrocyanosis and signs of haemolysis, which can become more pronounced after exposure to cold or in attacks. Acute, temporary cold agglutinin disease is usually preceded by an infection of the upper respiratory tract 2 to 3 weeks beforehand. Clinically, signs of hemolysis can be observed, which increase with rapid cooling.
AnalyteComplement loading on erythrocytes, cold autoantibodies against erythrocytes
indicationV. a. Cold agglutinin disease
material10 ml venous blood (native), drained out at 37 ° C / 10 ml EDTA blood
methodDirect and indirect anti-human globulin test, cold agglutinin test (hemolysis test) and cold agglutinin titration
Reference rangeNegative / cold agglutinin titre <128
ratingThe direct antiglobulin test is strongly positive with C3d. Cold agglutinins, mostly with specificity I or i, with a titer> 64 can be detected in the serum. While acute forms of AIHA usually heal spontaneously due to cold autoantibodies, patients with chronic cold agglutinin disease are to be protected above all from cooling. Care must be taken to ensure that blood is only transfused after it has been warmed with suitable equipment.
Differential diagnoses- Heat-type autoimmune hemolytic anemia
- Paroxysmal cold hemoglobinuria
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Paroxysmal cold hemoglobinuria (Donath-Landsteiner hemolysis)
Paroxysmal cold hemoglobinuria usually occurs acutely in children after a viral infection and is characterized by rapid intravascular hemolysis.
The Donath-Landsteiner antibodies on which the disease is based may be directed against cross-reactive epitopes of the pathogen.
AnalyteComplement loading on erythrocytes, Donath-Landsteiner antibodies
indicationV. a. Autoimmune hemolysis of the Donath-Landsteiner type
material10 ml venous blood (native) / EDTA blood (separated material)
methodDirect and indirect anti-human globulin test, hemolysis test
Reference rangenegative
ratingThe direct anti-human globulin test is positive with C3d. Bithermal hemolysins are found in the acute phase of the disease. The hemolytic symptoms are temporary and disappear after the infection has subsided.
Differential diagnoses- Heat-type autoimmune hemolytic anemia
- cold agglutinin disease
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Drug-induced immune hemolysis
About 20% of all autoimmune hemolytic anemias are said to be induced by drugs. Depending on the underlying pathomechanism, a distinction is made between different forms, the common feature of which is the formation of combination or neoantigens on erythrocytes caused by drugs. Antibody formation against these combination or neoantigens leads to immune hemolysis.
AnalyteAntibodies against erythrocytes
indicationV. a. Drug-induced immune hemolysis
material10 ml venous blood (native) / 10 ml EDTA blood / 10 ml urine; Specifying or sending in the suspicious medication (s)
methodAgglution test (direct and indirect antiglobulin test)
Reference rangenegative
ratingIn the most common forms of drug-induced immune hemolysis, the direct antiglobulin test is positive with IgG.
The indirect antiglobulin test only becomes positive in the presence of the causative drug. Not only the drug itself but also its metabolites can trigger autoimmune hemolysis and must also be investigated.
The most important therapeutic measure is the immediate discontinuation of the causative drug.
Differential diagnosesOther forms of autoimmune hemolysis
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Molecular genetic blood grouping
Determination and analysis of blood group antigens at allele level (AB0, RHD, RHCE, Kell, Duffy, Kidd, MNS, D-zygotia, D-weak and fetal Rhesus-D)
AnalyteAlleles coding for the respective blood groups
indication- Analysis of blood group variants, e.g. B. at V. a. weak D or partial D
- Clarification of uncertain antigen determinations (patients with AIHA, status after previous transfusions, status after bone marrow transplantation)
- Determination of fetal blood groups from amnion cells in case of suspected disease. M. haemolyticus neonatorum
- Clarification of genetic dispositions in high-risk pregnancies, e.g. in women of childbearing potential with irregular antibodies
- Forensic science
material10 ml EDTA blood, if fetal blood groups are determined 5 ml amniotic fluid / amnion cells
methodPolymerase chain reaction with sequence-specific primers (PCR-SSP)
Reference rangenot applicable
ratingThe molecular biological method is not recommended as the sole basis for determining blood groups. A serological determination should always be carried out.
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