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Clinical Pathology > Immunohematology > Flashcards

Immunohematology Flashcards

1
Q

What is immunohematology? What is its importance?

A

branch of hematology that studies antigen-antibody interactions as they relate to the pathogenesis and clinical manifestations of blood disorders

uses blood typing to identify possible risks of erythrocyte hemolysis during blood transfusions to find compatible blood donors

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2
Q

What determines blood groups?

A

species-specific inherited antigens present on the surface of RBCs

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3
Q

What are alloantibodies?

A

(isoantibodies) = naturally occurring antibodies against other blood types or foreign tissue present without prior exposure

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4
Q

Where do antibodies arise from?

A

“alien” antigens from transfusion, transplacentally, or trauma

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5
Q

What is neonatal isoerythrolysis (NI)?

A

hemolytic anemia that occurs in foals that inherit the sire’s blood group antigens (Aa, Qa) born to mares of a different blood types to the stallion

  • dam will have antibodies to the stallion/offspring RBCs in the colostrum
  • foal will be born healthy put undergo hypersensitivity after ingesting the colostrum
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6
Q

What 2 tests are performed during a transfusion? What is the point?

A
  1. blood typing
  2. crossmatching

classifies the animals blood type by determining with antigen(s) are present on the RBC membrane and if there are antibodies present in the serum

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7
Q

What is blood typing used to select? How does this happen?

A

permanent blood DONORS

uses an antiserum or a reagent to identify specific RBC antigens, causing a cross-reaction

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8
Q

What does crossmatching detect? How is this done?

A

if a recipient has antibodies in serum against a donor’s RBCs

patient serum is tested against a donor’s RBC or serum,
+ if a recipient’s antibodies attach to the RBC

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9
Q

What are the 2 types of antibodies to blood group antigens?

A
  1. naturally occurring (alloantigens)
  2. acquired after exposure to the blood group antigen
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10
Q

What are the 4 main causes of the development of anti-RBC antibodies? In what animal species does this naturally occur?

A
  1. transfusions
  2. cross-placental transfer during pregnancy (horse)
  3. vaccination with blood origin products
  4. autoimmune disease (IIMHA)

felines

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11
Q

What are the 8 major blood groups in dogs? Which ones are the most immunogenic?

A
  • DEA-1.1*
  • DEA-1.2*
  • DEA-3
  • DEA-4
  • DEA-5
  • DEA-6
  • DEA-7
  • DEA-8
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12
Q

What does it mean if a dog is DEA-1.1 or DEA-1.2 negative?

A

they have no naturally occurring antibodies

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13
Q

What is considered the universal donors and recipients in dogs?

A

DONOR - DEA-1.1 negative, DEA-4 positive

RECIPIENT - DEA1.1 positive

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14
Q

What dogs can receive blood from DEA1.1 negative donors? DEA1.1 positive donors?

A
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15
Q

What are 4 common signs of acute hemolytic transfusion reactions? What does this have the potential to do?

A
  1. severe intravascular hemolysis
  2. hemoglobinuria
  3. hyperbilirubinemia
  4. transfused RBCs only last <12h n vasculature making them useless

massive activation of immune and clotting systems leading to shock, renal failure, circulatory collapse, and death

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16
Q

What 6 breeds of dogs are likely to be universal donors? What blood type do they typically have?

A
  1. Greyhounds
  2. Boxers
  3. Irish Wolfhounds
  4. German Shepherds
  5. Dobermans
  6. Pit Bulls

DEA1.1 negative

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17
Q

What is the blood typing system like in cats?

A

AB system
- Type A (dominant)
- Type B
- Type AB

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18
Q

What species is at the highest risk of first-time transfusion reactions? Why?

A

cats - they have natural alloantibodies against other blood types

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19
Q

What is the most common blood type in cats in the USA? What species typically have this type? What are their antibody levels like?

A

A

DSH, DLH, non-pedigree cats

low levels of naturally occurring ant-B antibodies

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20
Q

What are the antibody levels in cats with type B blood like? What types of cats typically have this type?

A

high levels of anti-A antibodies

EXOTIC cats - British Short Hair, Abyssian, Himalayan, Cornish Rex, Devon Rex

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21
Q

What are the antibody levels in cats with type AB blood like?

A

no naturally occuring anti-A or anti-B antibodies (can receive any blood)

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22
Q

What kittens are in danger of neonatal isoerythrolysis? In what 2 breeds does this happen?

A

AB kittens born to a B queen and A/AB tom

  1. Devon Rex
  2. Birman cats
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23
Q

Feline blood groups:

A

A-B mismatches can cause fatal hemolytic reactions

24
Q

What are the levels of pre-existing alloantibodies like in large animals? For the most part, blood typing and transfusions are impractical and uncommon. What is the exception?

A

the presence of alloantibodies is rare

horses

25
Q

Single unmatched whole blood transfusions are well-tolerated in large animals. In what 2 situations should an animal be crossmatched?

A
  1. repeated transfusions
  2. plasma transfusions
26
Q

How many blood groups are there in horses? Which 3 are the most important? Most immunogenic?

A

7 blood groups and 30 RBC antigen types

A, C, Q

Aa, Qa* —> anti-Aa and anti-Qa antibodies lead to neonatal isoerythrocytosis

27
Q

When does equine neonatal isoerythrolysis typically develop in the foal? What kind of hypersensitivity is it?

A

newborn disease - first week of life

type II hypersensitivity causing hemolytic anemia

28
Q

What is the pathogenesis of equine neonatal isoerythrlysis? When does this most commonly occur?

A
  • mare starts to produce Ab against foal’s RBC inherited from the stallion
  • Abs are transferred into the colostrum

mare and stallion with different blood types —> mare is sensitized by the first pregnancy and starts to affect the second foal of the same mating pair

29
Q

How can a mare become exposed to blood from a fetus with different blood type to cause neonatal isoerythrolysis?

A

( MARE AND STALLION MUST HAVE DIFFERENT BLOOD TYPES - mares negative for RBC factors are also at higher risk)

  • placentitis
  • difficult parturition
  • foreign blood factors from previous transfusion
30
Q

What are the 5 clinical signs of foals affected by neonatal isoerythrolysis?

A
  1. lethargy, weakness
  2. icterus
  3. increased pulse rate and respiratory rate
  4. hemoglobinemia, hemoglobinuria
  5. severe hypoxia leading to convulsion, coma, and death
31
Q

How can neonatal isoerythrolysis be avoided in mares and foals before pregnancy? After?

A

screen mares for blood type and antibodies for compatibility with the stallion

test colostrum and avoid allowing foal to feed if it has anti-blood type antibodies (use frozen or another mare)

32
Q

Why are cows not commonly transfused?

A

over 80 RBC antigens yielding around 2 trillion blood types - impractical

  • single unmatched whole blood transfusions are generally safe and well-tolerated
  • crossmatch recommended for repeat transfusions
33
Q

How does blood typing and crossmatching compare?

A

BLOOD TYPING identified the RBC antigens on the cell surface to identify blood groups - DOESN’T detect antibodies between patient and potential donor

CROSSMATCHING identified antibodies against RBC antigens

34
Q

What are the 2 types of crossmatching? How are each done? What do the results mean?

A
  1. MAJOR: predicts if DONOR RBCs will be attacked by RECIPIENT antibodies (serum) - wash donor RBC in recipient serum
  2. MINOR: predicts if DONOR antibodies (serum) will attack RECIPIENT RBCs - wash recipient RBC in donor serum
  • hemolysis/agglutination = incompatible
  • no hemolysis/agglutination = compatible
35
Q

Crossmatch interpretation:

A
36
Q

How do cats compare with other animals with the need for crossmatching?

A

CATS - can naturally have alloantibodies against other blood types, so crossmatching is always required, even for the first transfusion

DOGS/HORSES - not common to have naturally occurring alloantibodies, so sensitization must occur before they develop antibodies - if it is 100% positive it is the animal’s first transfusion, a crossmatch is not necessary

37
Q

When do animals typically require transfusions?

A
  • acute anemia
  • hypovolemia
  • thrombocytopenia
  • hypoproteinemia
38
Q

What are the 5 characteristics of a good donor?

A
  1. blood-typed
  2. healthy with regular vaccines
  3. no RBC parasites, FeLV, FIV, or EIA
  4. never transfused
  5. free of most reactive antigens
39
Q

What are the best characteristics of dog, cat, and horse donors?

A

DOG - DEA-1.1 and DEA-1.2 negative

CAT - type A (can be B in certain regions)

HORSES - young geldings or females that have never been transfused or pregnant and lack Aa/Qa antigens

40
Q

What are the 2 types of blood transfusion reactions? What happens with each?

A
  1. IMMEDIATE (minutes to hours) - rapid intravascular hemolysis, hemoglobinemia, hemoglobinuria, fever, seizures
  2. DELAYED (7-10 days) - progressive anemia, icterus
41
Q

What are 2 possible non-RBC-related reactions to improper blood transfusions?

A
  1. transmission of infectious organisms, like Mycoplasma and Babesia spp. (screen donors!)
  2. sensitized patients to subsequent transfusion reactions
42
Q

In what animals is immune-mediated hemolytic anemia a possible consequence in improper transfusions? What kind of sensitivity is this?

A

dogs, occasionally cats

RBCs are destroyed by antibodies directed against them - Type II hypersensitivity

43
Q

What 3 things are commonly seen in a peripheral blood smear in immune-mediated hemolytic anemia?

A
  1. autoagglutination
  2. regenerative anemia
  3. spherocytes
44
Q

What are 3 major characteristics of acute immune-mediated transfusion reactions?

A
  1. severe intravascular hemolysis
  2. causes DIC, hypotension, shock, acute renal failure, and death
  3. induces a reaction from IgM and complement fixation (ghost cells)
45
Q

In what animals are acute immune-mediated transfusion reactions? Uncommon?

A

CATS - if type B cat is given Type A or AB blood, since they have naturally occurring alloantibodies

DOGS/HORSES - 1st transfusion is usually safe, reactions are caused by the presence of acquired antibodies

46
Q

What are 3 major characteristics of delayed immune-mediated transfusion reactions?

A
  1. mild extravascular hemolysis
  2. causes decreased PCV >24h and up to 2-3 weeks post-transfusion, hyperbilirubinemia, bilirubinemia, and a positive direct Coombs’ test
  3. induces a reaction from IgG and causes the formation of spherocytes
47
Q

When is it common for delayed immune-mediated transfusion reactions to occur?

A

1st transfusion in dogs - incompatible blood, sensitization to other antigens other than DEA-1.1 and DEA-1.2

48
Q

What are the 2 parts of the Coombs’ test? What do they detect?

A
  1. DIRECT ANTIGLOBULIN TEST (DAT) - detects anti-RBC antibodies or complement on the surface of RBCs
  2. INDIRECT ANIGLOBULIN TESt - detects anti-RNB antibodies in the serum of the patient using their serum against washed RBCs from sire, offspring, or possible donors
49
Q

In what animals does the Coombs’ test have no diagnostic value?

A

non-anemic animals

50
Q

What are the 6 steps to the procedure of the Coombs’ test for IMHA? What does a positive result mean?

A
  1. collect blood into an EDTA (purple top) tube
  2. wash erythrocytes
  3. suspend in buffered saline
  4. mix with species-specific Coombs’ reagent containint antiglobulins against IgG, IgM, and complement
  5. incubate at 37 degrees C for 30 mins
  6. centrifuge and check for agglutination/hemolysis

there is IgG, IgM, or C3 on the patient’s RBCs
(can have false negatives and positives!)

51
Q

What are 6 possible causes of false positives not associated with IMHA in the Coombs’ test?

A
  1. post-transfusion
  2. cross-reactive antibodies in Coombs’ reagent
  3. bacterial or particulate contamination of Coombs’ reagent
  4. in vitro complement binding during storage
  5. infections (Babesia, Mycoplasma)
  6. neoplasia (histiocytic sarcoma)
52
Q

What are 3 causes of negative reactions in animals with IMHA on the Coombs’ test? What is important to note about negative results?

A
  1. concentration of antibodies on RBCs is below sensitivity of the test
  2. previous treatment with steroids
  3. elution of weakly bound antibodies off the RBC during the washing step

negative results do not rule out IMHA

53
Q

What is the most common non-hemolytic reaction to transfusions? What kind of reaction is this? What is the cause?

A

febrile and allergic reactions - Type I hypersensitivity

IgE-mediated antibodies against allergens in donor blood, like antibiotics, chemicals from blood preparation, or albumin

54
Q

What are the 2 common signs of febrile and allergic transfusion reactions? What type of transfusion typically causes this?

A
  1. minor skin reactions, like pyoderma, edema, wheals, and pruritus
  2. in severe cases: hypotension, bronchiolar constriction, increased vascular permeability, and cardiopulmonary arrest

plasma transfusions, typically within 15mins to a few hours

55
Q

What should be done if a febrile and allergic reaction is observed during a blood transfusion?

A

stop transfusion and administer antihistamines

Clinical Pathology (33 decks)

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