Lecture 4: Immunohematology Flashcards
Define Immunohematology
studies antigen-antibody interactions as they related to pathogenesis and clinical manifestations of blood disorders
why is Immunohematology important
- Provide safe transfusion therapy
- Prevent NI
- Understand immune mediated mechanism of disease
define antigen
substance that is recognized as foreign and therefore can illicit an inflammatory response and production of antibodies
define alloantigen
Any antigen that is present in only some individuals of the same species and that illicit the production of alloantibodies in individuals that do not express that antigen
what is alloantibody
an antibody produced in response to introduction of alloantigen that is not expressed in that animal
what Ig’s are produced in type II hypersensitivity reactions
IgG and IgM
In type II hypersensitivity reactions is the antigen soluble or cell bound
cell bound
what is the mechanism for type II hypersensitivity reactions
IgG or IgM bind to self antigen
what are some examples of type II hypersensitivity reactions
- IMHA
- NI
- Transfusion reactions
what is alloimmunity
sensitization, formation of antibodies against alloantigens
what causes alloimmunity to occur
- Blood transfusions
- Vaccination with blood products
- Sensitization of dam transplacentally or from exposure at birth
what are naturally-occurring antibodies
antibodies to blood group antigens not expressed in that individual, no known previous exposure to these antigens
what is an example of naturally-occurring antibodies
type B cats
blood group antigens are inherited as ___ or __
autosomal dominant or co-dominants
what is blood typing
process of classifying an animals blood type by determining which antigens are present on rBC membranes
Order species most to least at risk of transfusion reactions
cats> dogs > equine> bovine
what are the two most antigen blood groups in dogs
DEA- 1.1, DEA 1.2
is an incompatible blood transfusion more dangerous the first or second exposure
second
natural antibodies against DEA 1.1 or DEA 1.2 are extremely rare, making first time transfusions relatively __ without typing
safe
In dogs, transfusion reactions are usually result of ___
DEA 1.1 or DEA 1.2 negative dogs receiving 2 or more tranfusions from DEA 1.1 or DEA 1.2 positive dog
which species have natural alloantibodies against other blood types
cats
in which species is a first time blood transfusion always a risk without blood typing
cats
Type A cats are born with antibodies against __
B
type B cats are born with antibodies against __
A
type AB are born with __ antibodies because has both A and B
no antibodies
what is the most common blood type in cats
type A
type A cats have __ levels of naturally occurring anti-B antibodies
low
type B cats have __ levels of anti-A antibodies
high
what breeds are more likely to be type B in cats
British shorthair, Devon Rex, Abyssinian, Himalayan
what is the universal recipient blood type for cats
type AB
t or f: type AB cats can donate blood
false
what are the most antigen blood types in horses and what is a major associated disease
A and Q
Disease: NI
what are some immediate reactions to blood transfusions
- Rapid hemolysis
- Hemoglobinuria, hemoglobin edema (intravascular hemolysis)
- Fever
- Seizures
what are some examples of delayed reactions from blood transfusions
- Progressive anemia
- Icterus
what species have minimal natural antibodies and therefore first time transfusions are usually safe without blood typing
dogs and horses
which species plasma contains natural anti-erythrocyte antibodies and first time transfusions without typing are not safe
cats
What is neonatal isoerythrolysis
lysis of neonatal RBC’s due to maternal antibodies direct against neonate RBC antigens
what is difference between NI and IMHA
IMHA antibodies are produced by the same animal who has reaction, in NI antibodies are produced by mare
in NI after newborn ingests colostrum from dam they develop signs of __ within hrs or days
hemolytic anemia- weakness, hemoglobinema, hemoglobinuria, icterus
how can you test for/ prevent NI
coomb’s test on newborn or cross- match between newborn RBC’s and maternal serum
are firstborn or second born foals to mare with antibodies against RBC more affect
secondborn foals
are the mares of foals Aa or Qa positive and describe what happens
Mares are negative, Foals are Aa or Qa+ and sensitized to Aa- or Qa- negative mares—> foals ingest A or Q antibodies from mare colostrum—> RBC hemolysis
what is tx for NI
transfuse foal with mares washed RBC’s (not sires)
why would you not want to transfuse NI foal with sire’s RBC
foal has anti-sire antibodies from mares colostrum
what are some clinical signs of NI
lethargy, weakness, tachycardia, tachypnea, bilirubinemia (hemolysis), Hematuria, acute renal injury
how would cats get NI
occurs in A or AB kittens born to a B queen, B queen makes antibodies against A
how can dogs get NI
occurs in DEA 1.1 + pups born to previously sensitized DEA 1.1 - bitch
IMHA most common in what species
dogs
MOA of IMHA
RBC’s destroyed by antibodies direct against them
what would you see on blood smear with IMHA
- Autoagglutination
- Regenerative anemia
- Spherocytosis
blood smear from dog with suspected IMHA- how does this support that dx
autagglutination, spherocytes
Is IMHA intravascular or extravascular hemolysis
extravascular and intravascular
what Ig is most commonly seen with IMHA
igG
what abnormal RBC is seen in extravascular IMHA and how does that happen
spherocytes- portion of RBC membrane removed by splenic macrophages
what is the mechanism of intravascular IMHA
fixation of complement—> MAC complexes poke holes in RBC’s
what abnormal RBC is seen with intravascular IMHA
ghost cells
t or f: can have false positive and negative results for Coombs testing for IMHA
true
t or f: a negative Coombs test does not rule out IMHA
true
case ex: 6yr MC mix breed dog with 1 week hx of lethargy, exercise intolerance. PE- icterus. Characterize the erythron and thrombin.
Blood smear showed: marked spherocytes, ghost cells, marked anisocytosis, marked polychromatic
Provide top differentials
- Low hematocrit- anemic
- MCV high- macrocytic
- MCHC low- hypochromic
- High retics- regenerative
- Appropriate metarubriocytosis
- Thrombocytopenia
Spherocytes: extravascular hemolysis
Ghost cells: intravascular hemolysis
Icterus- intravascular hemolysis
Top dx: IMHA with immune mediated thrombocytopenia—> Evans syndrome
case ex: 3 day old foal, hx of weakness since brith, red tinged urine, icterus mm. Mares third foal.
Blood smear: monocytes that contain phagocytized erythrocytes
Characterize the erythron and top dx
- Low hematocrit- anemic
- MCV normal- normocytic
- MCHC: normal- normochromic
- Red tinged urine- intravascular hemolysis- hemoglobinuria
- Icterus- intravascular hemolysis
Top dx: NI
