AIHA -Autoimmune Haemolytic Anaemias

A brief look at the various types

1. IMMUNE HAEMOLYTIC ANAEMIAS Dr Brian Mitchelson

2. IMMUNE HAEMOLYTIC ANAEMIA General Principles All require antigen-antibody reactions Types of reactions dependent on: Availability of complement Environmental Temperature Functional status of reticuloendothelial system Manifestations Intravascular haemolysis Extravascular haemolysis 2

3. IMMUNE HAEMOLYTIC ANAEMIA General Principles - 2 Antibodies combine with RBC, and either: Activate complement cascade, &/or Opsonize RBC for immune system If 1: if all of complement cascade is fixed to red cell, intravascular cell lysis occurs If 2: &/or if complement is only partially fixed, macrophages recognize Fc receptor of Ig &/or C3b of complement & phagocytize RBC, causing extravascular RBC destruction 3

4. IMMUNE HAEMOLYTIC ANAEMIA Coombs Test - Direct Looks for immunoglobulin &/or complement of surface of red blood cell (normally neither found on RBC surface) Coombs reagent - combination of anti-human immunoglobulin & anti-human complement Mixed with patient’s red cells; if immunoglobulin or complement are on surface, Coombs reagent will link cells together and cause agglutination of RBCs 4

5. IMMUNE HAEMOLYTIC ANAEMIA Coombs Test - Indirect Looks for anti-red blood cell antibodies in the patient’s serum, using a panel of red cells with known surface antigens Combine patient’s serum with cells from a panel of RBC’s with known antigens Add Coombs’ reagent to this mixture If anti-RBC antigens are in serum, agglutination occurs 5

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7. HAEMOLYTIC ANAEMIA - IMMUNE Autoimmune Haemolysis -2 types: Warm autoimmune haemolysis Cold autoimmune haemolysis Alloimmune Haemolysis Haemolytic Transfusion Reaction Haemolytic Disease of the Newborn Drug-Related Haemolysis 7

8. Autoimmune H aemolytic Anaemia (AHA) Autoimmune haemolytic anaemia (AHA) is characterized by shortened red blood cell (RBC) survival and the presence of autoantibodies directed against autologous RBCs. 8

9. AUTOIMMUNE HAEMOLYSIS Due to formation of autoantibodies that attack patient’s own RBC’s Type characterized by ability of autoantibodies to fix complement & site of RBC destruction Often associated with either lymphoproliferative disease or collagen vascular disease 9

10. Autoimmune Haemolytic Anaemia Classified by thermal reactivity Warm reacts near 37 o C, Cold at 0-4 o C Serologic evidence is positive DAT (direct Coomb’s test) with IgG or C3d present Indirect Coomb’s test and specificity (serum / eluate) Diagnostic Criteria- serologic evidence and laboratory or clinical haemolysis 10

11. AIHA Classification Warm autoimmune haemolytic anaemia Idiopathic, Secondary ( Lymphoproliferative disorders, autoimmune dise ases) Cold autoimmune haemolytic anaemia Cold agglutinin syndrome ( Idiopathic, Secondary- mycoplasma, infectious mono, LPD ) Paroxysmal cold haemoglobinuria ( Idiopathic, Secondary- measles, mumps, syphilis ) Drug-induced IHA ( Autoimmune, Drug adsorption, Neoantigen ) 11

12. AUTOIMMUNE HAEMOLYSIS Warm Type Usually IgG antibodies Fix complement only to level of C3,if at all Immunoglobulin binding occurs at all temps Fc receptors/C3b recognized by macrophages Haemolysis primarily extravascular 70% associated with other illnesses Responsive to steroids/splenectomy 12

13. Diagnosis Anaemia. Spherocytes in peripheral blood film . Reticulocytes are increased. Neutrophilia common. RBC coated with IgG, complement or both (detect using DAT). Autoantibody —often pan-reacting but specificity in 10–15% (Rh: mainly anti-e, anti-D or anti-c). 13

14. Diagnosis LDH increased . Serum haptoglobin decreased. Exclude underlying lymphoma (BM, blood and marrow cell markers). Autoimmune profile—to exclude SLE or other connective tissue disorder. 14

15. AUTOIMMUNE HAEMOLYSIS Cold Type Most commonly IgM mediated Antibodies bind best at 30º or lower Fix entire complement cascade Leads to formation of membrane attack complex, which leads to RBC lysis in vasculature 90 % associated with other illnesses Poorly responsive to steroids, splenectomy Responsive to plasmapheresis 15

16. Diagnosis Anaemia. Reticulocytes are increased. Neutrophilia common. Positive DAT—C3 only. ± Autoantibodies —IgG or IgM – Monoclonal in NHL. – Polyclonal in infection-related CHAD. IgM antibodies react best at 4°C (thermal amplitude 4–32°C). Specificity 16

17. Diagnosis Anti-I (Mycoplasma). Anti-i (infectious mononucleosis)—causes little haemolysis in adults Since RBCs have little anti-i (cf. newborn i >> I). LDH increased. Serum haptoglobin decreased. Exclude underlying lymphoma (BM, blood and marrow cell markers). Autoimmune profile to exclude SLE or other connective tissue disorder. 17

18. IMMUNE HAEMOLYSIS Drug-Related Immune Complex Mechanism Quinidine, Quinine, Isoniazid “Haptenic” Immune Mechanism Penicillins, Cephalosporins True Autoimmune Mechanism Methyldopa, L-DOPA, Procaineamide, Ibuprofen 18

19. DRUG-INDUCED HAEMOLYSIS Immune Complex Mechanism Drug & antibody bind in the plasma Immune complexes either Sit on red blood cell Antigen-antibody complex recognized by RE system Red cells lysed as “innocent bystander” of destruction of immune complex REQUIRES DRUG IN SYSTEM 19

20. DRUG-INDUCED HAEMOLYSIS Haptenic Mechanism Drug binds to & reacts with red cell surface proteins Antibodies recognize altered protein, ± drug, as foreign Antibodies bind to altered protein & initiate process leading to hemolysis 20

21. DRUG-INDUCED HAEMOLYSIS True Autoantibody Formation Certain drugs appear to cause antibodies that react with antigens normally found on RBC surface, and do so even in the absence of the drug 21

22. Drug-Induced Autoimmune Haemolytic Anaemia Prototype Drugs Clinical Findings Detection of Drug-Induced Antibody Proposed Mechanism Stibophen Acute Intravascular Haemolysis Serum + Drug + Red Cells Neoantigen Penicillins/ Cephalosporin Subacute Extravascular Haemolysis Serum + Drug-Coated Red Cells Drug Adsorption α-methyldopa Warm antibody autoimmune haemolytic anaemia Serum + Normal Red Cells Autoimmune 22

23. Drug-Induced Positive Antiglobulin Tests Mechanism DAT Serum and Eluate Neoantigen -Drug +RBC complex C3 (sometimes IgG also) Serum reacts with rbcs only in the presence of drug; eluate non-reactive Drug Adsorption (DA) -Drug binds to RBC IgG (sometimes C3 also) React with drug-coated RBCs but not untreated RBCs- Ab to drug Autoantibodies -WAIHA IgG (rarely C3 also) 11-36% of pts React with normal RBCs in absence of drug 23

24. Treatment - AIHA WAIHA CAD PCH Drug-IHA Folate Corticosteroids 20% complete response Folate Avoid cold Treat secondary cause Folate Avoid cold Treat if haemolysis present Splenectomy 60-75% response rate Chlorambucil Cytoxan, α - Interferon Treat infection Folate Stop drugs Cytotoxic drugs-Cytoxan, Rituxan Plasmapheresis ? Plasmapheresis Corticosteroids-severe cases Transfuse –least incompatible Transfuse-I+, blood warmer Transfuse- P+, blood warmer Transfuse 24

25. ALLOIMUNE HAEMOLYSIS Haemolytic Transfusion Reaction Caused by recognition of foreign antigens on transfused blood cells Several types Immediate Intravascular Haemolysis ( Minutes ) - Due to preformed antibodies; life-threatening Slow extravascular haemolysis ( Days ) - Usually due to repeat exposure to a foreign antigen to which there was a previous exposure; usually only mild symptoms Delayed sensitization - ( Weeks ) - Usually due to 1st exposure to foreign antigen; asymptomatic 25

26. ALLOIMMUNE HAEMOLYSIS Testing Pre-transfusion ABO & Rh Type of both donor & recipient Antibody Screen of Donor & Recipient, including indirect Coombs Major cross-match by same procedure (recipient serum & donor red cells) 26

27. Manifestations of Delayed Haemolytic Transfusion Reactions Clinical Fevers Chills Symptoms of anaemia Jaundice Oliguria or anuria (uncommon) Generalized Bleeding (Rare) Laboratory Unexplained anaemia (or decrease in haemoglobin ) Positive direct antiglobulin test Haemoglobinemia Haemoglobinuria (Uncommon) Haemosiderinuria Decreased haptoglobin Responsible antibody in post-transfusion RBC eluate 27

28. ALLOIMMUNE HAEMOLYSIS Haemolytic Disease of the Newborn Due to incompatibility between mother negative for an antigen & foetus/father positive for that antigen. Rh incompatibility, ABO incompatibility most common causes Usually occurs with 2nd or later pregnancies Requires maternal IgG antibodies vs. RBC antigens in foetus 28

29. HYDROPS FETALIS 29

30. ALLOIMMUNE HAEMOLYSIS Haemolytic Disease of the Newborn - #2 Can cause severe anaemia in foetus , with erythroblastosis and heart failure Hyperbilirubinaemia can lead to severe brain damage (kernicterus) if not promptly treated HDN due to Rh incompatibility can be almost totally prevented by administration of anti-Rh D to Rh negative mothers after each pregnancy 30

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33. The End Thank you for your attention. 33