Hypersensitivities 2 Flashcards
Clinical signs of Type II hypersensitivities
- Agglutination
- Spherocytes- cells without central pallor, RBC lysis
- Hemolysis- RBC break down
Type II hypersensitivity
- Destruction of cells due to the binding of antibodies (IgG/IgM) to the cell surface
- Results in damage and cell destruction mediated by NK cells, complement, phagocytic cells
Type II hypersensitivity reactions
Antibody mediated cell lysis occurs as normal to kill infected cells, but the hypersensitivity begins when we start to destroy cells due to antibody binding
- The Antibody binds to cell, activates Complement, phagocytic cells or NK cells
Immune-mediated destruction of RBCs or platelets
- Occurs due to antibody binding to the RBC
- Two means of destruction: phagocytosis in the spleen or complement-mediated lysis in blood
Extra-vascular hemolysis
Phagocytosis of RBCs in the spleen in immune-mediated destruction
Intra-vascular hemolysis
- Complement-mediated lysis during immune mediated destruction of RBCs
- Occurs mainly in bloodstream
Immune mediated hemolytic anemia (IMHA)
- Form of immune mediated destruction of RBCs
- Most seen in dogs, middle aged, females, strong breed associations/genetics
Antibody targets for immune mediated hemolytic anemia (IMHA)
- Self RBC antigens- autoimmune
- Alloantigen antigens- occur from transfusions of RBCs
- Foreign antigens absorbed to the cell surface- innocent bystander for example during infections)
- Altered self (RBC) antigen- can be caused by drugs, microbes, toxins altering the normal protein structure or create new epitopes in the altered self-antigens
- Exposed cryptic antigens- epitopes are normally hidden but become visible during inflammation
Blood groups
RBCs express cell surface molecules (glycoproteins and glycolipids) that can act as antigens
- Many different genes that encode for these antigens and result in different blood groups
EA= erythrocyte antigens
Blood transfusion potential issues
- Antibodies in the serum of the donor can recognize recipient RBCs but this usually has milder effects
- Antibodies in the recipient can react with the antigens on the RBCs from the donor
Effects of issues with blood transfusions
Since RBCs all have their own antigens, when we do blood transfusions there are antibodies that can bind to these different antigens, cause lysis via complement or opsonization
- If large amounts of RBCs are being lysed, it can cause serious disease (blood clotting, disseminated intravascular coagulation)
Complement system in large amounts can result in anaphylaxis and shock etc.
Cross-matching
- testing for antibodies against different blood groups
- overall don’t want agglutination
Major vs. minor cross matching
major
- mix recipient serum with donor cells. Don’t want any of the recipient antibodies to be up against the donors RBCs
minor
- mix donor serum with recipient cells
- looks at whether there are antibodies in the donor serum that will react to the recipients RBCs
Hemolytic disease of the newborn (HDN) or Neonatal isoerythrolysis
Newborn has both alloantigens from mother and father. Memory responses can cause worsening with repeated pregnancies
- Disease often occurs when there are tears in the placenta
- Allow fetal cells to enter the maternal blood and cause the mother to mount an immune response to the foreign blood group antigens
- Mother is sensitized to the antigen and therefore makes antibodies against it
- Antibodies concentrate in the colostrum and are passed on to the neonate
- Colostral antibodies cause RBC lysis in newborn
Clinical signs of HDN
- Anemia
- Jaundice
- Lethargy
- Anorexia
- Death