Immune Hemolysis Flashcards
(25 cards)
What types of antibodies does the DAT (Coombs) Test detect? Where is the antibody?
IgG antibodies or complement C3 on patients red cells
What types of antibodies does IAT (Coombs) Test detect? Where is the antibody?
detects IgG antibodies against RBC, its found in the patient serum
Where does the majority of immune hemolytic anemia occur- extravascular or intravascular?
mostly in extravascular (Ab-coated RBC ingested by macrophages) with the exception of ABO transfusion rxn
Which antibody are the spleen and liver best at removing from the blood?
spleen is most efficient clearing RBC coated with IgG and liver is more efficient in clearing sensitized by IgM (and complement over C3)
Name some common causes of autoimmune hemolytic anemia.
many are idiopathic, other are associated with autoimmune disease, lymphoproliferative disorder (esp CLL) infection, etc.
What smear/lab results would be suggestive of hemolysis due to warm autoantibodies?
DAT will be positive for IgG +/- C3 peripheral blood shows spherocytes, not bite cells, young shift cells may be present
How might you treat someone with hemolysis duet o warm autoantibodies?
corticosteroids splenectomy (relapse) rituximab transfusion (although crossmatch may be difficult)
Cold agglutinin syndrome is _____ antibody-mediated.
IgM, and most commonly target I or i antigens Note: hemolysis is more likely if antibody binds RBC at or near body temperature (measured by thermal amplitude), most are clinically benign
Cold agglutinin syndrome can be a complication of the which infections?
mycoplasma, EB virus or lymphoproliferative disorders
What is the smear/lab result indicating cold agglutinin (think antibodies).
DAT positive for C3 and negative for IgG smear shows groups of RBC that appear to be clumping together, clumping can be seen macroscopically
What is acrocyanosis?
slugging of blood that may occur with cold agglutinin syndrome can be clinically apparent with livedo reticular or associated with Raynaud’s syndrome
What can we do to treat cold agglutinin disease?
alternative immunosuppression and avoid cold exposure (corticosteroids or splenectomy are often ineffective)
Given the mechanism of drug-induced hemolysis, name the likely antibody and location of hemolysis: drug binds RBC membrane, antibody binds to drug-membrane complex. (haptenic)
IgG antibody, extravascular hemolysis (often Beta-lactam)
Given the mechanism of drug-induced hemolysis, name the likely antibody and location of hemolysis: drug binds antibody in plasma, immune complex deposits on RBC membrane. (immune complex)
IgM antibodies with complement fixation, intravascular hemolysis (often quinidine)
Given the mechanism of drug-induced hemolysis, name the likely antibody and location of hemolysis: drug stimulate immune system to make autoantibodies.
IgG antibodies, extravascular
This theory explains why some drugs can cause hemolysis with first exposure.
“induced-fit” hypothesis: where drug increases affinity of pre-formed antibody to RBC membrane
What are consequences of hemolytic disease in a fetus?
severe hemolysis may cause liver injury from extra medullary hematopoiesis, hydrous fetalis, and intrauterine death unconjugated bilirubin may cause brain damage (kernicterus)
Why is ABO fetus-mother incompatibility usually mild or asymptomatic?
ABO antibodies are IgM, don’t cross placenta well ABO antigens compete with antibody for RBC binding ABO antigens re less well developed at birth
Why does maternofetal ABO incompatibility make sensitization to non-ABO antigens less likely?
ABO antibodies tend to destroy cells before they can cause an immune reaction
How can you treat hemolytic disease of the newborn?
exchange transfusion (O neg RBC) for severe anemia phototherapy for hyperbilirubinemia intrauterine transfusion or early delivery in select cases **prevention is best treatment
How do you prevent non-ABO immune hemolysis in the fetus?
prevent sensitization of the mother: never give Rh+ blood to Rh- woman Administer Rh immune globulin after delivery or abortion
What might be expected on the smear of a person undergoing hemolytic anemia? What is the most important lab result in this situation?
polychromasia, many spherocytes, H-J body; most important lab test is reticulocyte count
Which of the following are not a cause of hemolysis: prosthetic valve, mild hypothyroidism, chemotherapy/radiation, chronic GI blood loss?
only mechanical valve would cause hemolysis, the rest simply lead to anemia
