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Clinical Pathology > Immunohematology > Flashcards

Immunohematology Flashcards

1
Q

Define immunohematology.

A

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

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2
Q

Why is immunohematology important?

A

Importance: for blood typing and identification of possible risks of
erythrocyte hemolysis during blood transfusion
* Compatible blood donors!

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3
Q

Blood groups are divided based on?

A

Species-specific antigens on surface of RBCs
Antigens are inherited.

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4
Q
  • Transfusion reactions in Neonatal isoerythrolysis.
    Also in IMHA

Antigens can vary in immunogenicity

Feline blood group, A and B antigens are det. by four most specific glycoprotiens on erythrocyte membrane

A
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5
Q
  1. Allantibodies are also called?
  2. What are alloantibodies?
  3. Is this common?
A
  1. Alloantibodies AKA isoantibodies
  2. Alloantibodies are naturally occurring antibodies against another blood type present in animal’s plasma from birth, against blood-type antigens WITHOUT prior exposure.
  3. No, not in vet med
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6
Q

Antibodies against erythrocyte antigens are produced in response to antigen ______.

How do they form?

A

aliens
2. Through transfusion or transplacentally

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7
Q

What is Neonatal isoerythrolysis (NI)?

A

Asoci. with Incompatibility in blood.

  1. An infant is born healthy but then develops a hemolytic anemia due to hypersensitivity reaction that happens within hours or even days after newborn ingests its mothers colostrum. Reaction between antibody produced by mother present in colostrum, Ab directed against the RBCs, blood group antigens, that the infant inherited from the father. Seen in horses, cats, dogs.

that occurs in foals that inherit their sire’s blood group antigens (Qa and Aa) born to mares of a different blood
type to the stallion they were mated to
Dam has antibodies to an alien RBC antigen on offspring’s RBCs

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8
Q

Why are Blood typing & Crossmatching important?

A

Both are performed prior to transfusion. This process classifies an animal’s blood type by determining which
antigen(s) are present on RBC membranes

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9
Q

What is blood typing used for?
* Used to select permanent blood _______
* Uses “_________” or a reagent to Identify specific RBC Antigen (Ag)
* Antiserum cross reacts with _______ RBC ___
* Finds blood ______ of a species

A
  • Used to select permanent blood donors
  • Uses “antiserum” or a reagent to Identify specific RBC Antigen (Ag)
  • Antiserum cross reacts with Specific RBC Ag (antigen)
  • Finds blood group of a species
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10
Q

What is cross matching used for?
* Used to detect if recipient or donor have ____ in _____ ______ each other’s RBCs
* Uses patient serum against donor’s _____ or donor’s ______
- __________ Ab attach to the RBCs of the ______ after transfusion.

Transfusion performed with untype/crossmatched blood can _________ recipients to future transfusions or result in reactions that range from enhanced _______ of transfused RBCs or even ____ of patient.

A
  • Used to detect if recipient or donor have Ab in serum against
    each other’s RBCs
  • Uses patient serum against donor’s RBCs or donor’s serum
  • Recipient’s Ab attach to the RBCs of the donor after transfusion.

Transfusion performed with untype/crossmatched blood can sensitize recipients to future transfusions or result in reactions that range from enhanced removal of transfused RBCs or even death of patient.

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11
Q

There are 2 types of Ab to blood group antigens

A
  1. naturally occurring Ab
  2. acquired Ab, after exposure to the blood group Ag
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12
Q

Anti-RBC antibodies can result from?

A
  • Transfusions
  • Cross-placental transfer during pregnancy in the horse
  • Vaccination with blood origin products
  • Autoimmune disease (such as IMHA)
  • Naturally in felines

Ideally any animal routinely used as blood donor should be blood typed for the most common antigens that produce hemolytic reaction and ideally should be - for these antigens.

Crossmatching should always be performed in an individual that has been previously exposed to blood group antigens. why? B/c the patient has most likely developed Ab against those blood group antigens and therefore can no longer receive that blood type.

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13
Q

What are the 8 major blood groups in dogs?

A

DEA = dog erythrocyte antigen
Dogs can be +, -, or both to these two types. DEA 1.1 and 1.2 - dogs have no naturally occurring antibodies, so most have prior exposure or sensitization usually from previous transfusion.

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14
Q

New dog blood groups in ?

A

Dalmatian, doberman pinschers

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15
Q

Dogs can be + for either DEA 1.1 or 1.2 but they can not be?

A

Positive for both

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16
Q

Dogs can be - for ?

A

BOTH DEA 1.1 and 1.2

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17
Q

DEA 1.1 + means?

A

There is 1.1 antigens on RBC surface.

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18
Q

DEA 1.1 - means?

A

No 1.1 antigens on RBC surface

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19
Q

What is the Canine blood type compatibility that should
be used for transfusion?

A

DEA 1.1 + = universal recipients b/c they can receive transfusion from all blood types w/o major complication/reaction risks. 60% of dog population has this blood type.

DEA 1.1 + = should not be transfused into DEA 1.1 - dogs. If DEA 1.1 - recip receives DEA 1.1 + blood –> sensitized to DEA 1.1 blood by alloantibody formation if its the first transfusion –> Shorten RBC life span and forever sensitized to DEA 1.1 blood. If it is the 2nd transfusion, the life threatning conditions will follow within hours;. Alloantiodies will also be present in bitch milk and adversely affect health of DEA 1.1 - puppies. So or best practices, if donor is DEA 1.1 + and the refip is DEA 1.1 - DO NOT TRANSFUSE RECIP.

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20
Q

What are reactions in a case of acute hemolytic transfusion?

A
  1. Severe Intravascular Hemolysis
  2. Hemoglobinuria
  3. Hyperbilirubinemia
  4. Transfused RBCs remain in vasculature < 12h – useless
  5. Potential for massive activation of the immune and clotting systems – leading to shock, renal failure, circulatory collapse, and death
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21
Q

Which breeds more likely to be universal donors?

A

B/c they are more often DEA 1.1 -
* Greyhounds,
* Boxers,
* Irish Wolfhounds,
* German Shepherd Dogs,
* Dobermans,
* Pit Bulls

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22
Q

What are the Blood types (groups) in Cats?

A

Inherited as simple autosomal trait. Type A is dominant over B.
Inheritance of AB allele is unknown; it is not due to poor dominance of A and B?
% of Type A or Type B + is breed dependent.

**Cats that have nat antibodies against other blood types have the highest risk of… (see inmage)

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23
Q

Type A Blood in cats have what antigen on RBCs?
What is the % commonality?
What breeds are affected?
What antibodies do they have?

A
  1. Has antigen A on RBCs
  2. Most common in USA ~95% in DSH, DLH, Non-pedigree cats
  3. Low levels of naturally occurring anti—B Antibodies. Hemolysins consist of = amts of Ig G and Ig M??

~1/3 of type A cats have macroscopic agglutinins and hemolysins
• In other words, they have have low level of naturally occurring Anti-B Antibodies.
In theory, do not need to crossmatch type A cats (or breeds with high likelihood of
being cat A) if transfusing with blood from another type A cat

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24
Q

Type B Blood in cats have what antigen on RBCs?
What is the % commonality?
What breeds are affected?
What antibodies do they have?

A

Type B Blood
* Antigen B on RBCs
* High levels of anti-A antibodies
* It is a less common Type blood than Type A
* Exotic ad British Short Hair cats, Abyssinian, Himalayan, Cornish Rex,
Devon Rex

high titer anti-a hemagglutins and hemoluysisns mainly of IgM class with lesser amt of IgG.

More common outside US.

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25
Q

Type AB Blood in cats have what antigen on RBCs?
What is the % commonality?
What breeds are affected?
What antibodies do they have?

A

Type AB Blood
* Antigen A and B on RBCs
* No naturally occurring anti-A or anti-B antibodies
* AB kittens born to a B queen are in danger of neonatal isoerythrolysis,
but can safely receive A or B blood

Both express A antigen and safely receive Type A and B products. Queen = Type B made it to type A or AB toms can produce type a and AB kittens.

Very rare to find Type AB cats. Kittens are at risk for neonatal isoerythrolysis.

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26
Q

A-B mistmaches can cause fatal hemolytic reactions.

A

Neonatal isoerythrolysis can occur, but rare, except for Devon Rex, and Birman
Plasma of type B cats (older than 3 months) have very strong naturally occurring anti-
A alloantibodies (Boys hate Alcatraz)
A-B mismatches can cause fatal hemolytic reactions
DNA test is available to identify the b allele, allowing identification of type B cats or
cats carrying the allele
Important to identify cats lacking the type A antigen (i.e., type B cats)

27
Q

Are blood transfusions in large animals common?

A

No due to variability between species.

28
Q

Pre-existing alloantibodies are rare in which speices?

A

Horse, cattle, sheep, goat, pig, llama, alpaca

29
Q

In large animal:
Blood-typing impractical – except in _______
* Transfusions uncommon – except _____
* Single __________ ______ blood transfusions tend to be well- tolerated
* Crossmatch if you are going to:
1. ________ transfuse an animal
2. Give a ______ transfusion

A

horses, horses, unmatched, whole, Repeatedly, plasma

30
Q

What are the blood groups in equine?

A
  • 7 blood groups and 30 RBC antigen types
  • > 400,000 blood types
  • Antigens A, C and Q are the most important
  • Aa & Qa very immunogenic and are therefore the most important
  • Anti-Aa antibodies or Anti-Qa Antibodies can lead to neonatal isoerythrolysis
  • No Universal donor
  • No need to Crossmatch for first transfusion as long as you are sure that this is the first transfusion. Once transfusion as occurred in a horse, a cross match should be performed prior to ANY subsequent transfusion to detect AB that may have been produed against a different RBC antigen.;
  • Need sensitization

Qa = responsible for 90% of all cases of neonatal isoerythrolysis in horses. Qa antigen is extremely rare in certain breeds, eg. standardbreds.

31
Q

What is Equine Neonatal Isoerythrolysis?
What type of hypersensitivity reaction is it?

A
  • It is a hemolytic anemia that is classified as a Newborn disease in foals.
  • First week of life
  • Type II hypersensitivity
  • When blood type of mare is diff from stallion and foal. Inherits sensitizing RBC from stallion. MAres are - for RBC factor have the potential to develop Ab against those facotrs. Mares can become sensitized to exposure of fetus blood with incopatible blood type. Mare sensitive to stallion RBCs. Will produce alloantibodies. Immunoogic memory can persist for manby years. Sensitization after inital exposure is usually minimal, Reeated exposure to same RBC antigen occurs with subseq. pregnancies then alloantibody produc will increase considerably. Mare produces Ab against foal’s RBCs
  • Transfers those Ab to the foal via colostrum
  • Blood type of mare is different than the stallion
  • Foal inherits the sensitizing RBCs from the stallion
  • Risk: Mares negative for RBCs factors
  • Exposure to blood of fetus with incompatible blood type
  • placentitis , difficult parturition, foreign blood factors from previous blood transfusion
32
Q

What happens to the dam as a result?
What happens to the foal? Be specific as to whether this is the first foal, second foal, etc that is birthed from this dam.
What are the clinical signs of disease?

A

Equine Neonatal Isoerythrolysis
* Dam becomes sensitized to Ag on foal RBC inherited from sire
* Mare develops Abs to sire-derived RBC Ag
* Usually 2nd Foal: born healthy, ingests colostrum, 2-5 d later…
§ Most cases –> No / subclinical disease & spontaneous recovery
§ Clinical disease:
o Lethargy, weakness, icterus
o ↑ pulse rate ↑ respiratory rate
o If severe: hemoglobinemia & hemoglobinuria
o Severe hypoxia = convulsion / coma / death

Colostrum Ab absorbed into foal circulation in first few hours after both until gut closure. Macromolec. can not be absorbed into blood from GI tract. Mare develops AB to sire derived RBC in foal because they differ to their RBC antigens. Harmful alloAb bind to offedning ag on foal –> HA and extravascular/intravasc hemolysisl. The hgher the mare AB to offending RBC antigen then the higher the risk for developing isoerythrolysis

33
Q

How to prevent?

A

First step must be taken before breeding. Must blood type and Ab screen mare to check if any issues/access compatibiltiy with stallions.
Only mares that lack AA and QA antigen can form ab against it. These mares should be matched to a stallion that are al,so negatigve. Some breeds have high prevlence of AA and QA antigens, such as thoroughbreeds, meaning suitable stallion hard to find

Another way to prevnt: test mares serujm for anti erythrocyte ab about 1-2 weeks before foaling.

Testing de4termine whether a foal will develop neonatal isoerythrolysisl.

If ab screen is + for litic antibodies - recomend foal not to ingest colostrum for 24-48 after birth and maybe adminstered alternative source of colostrum.

34
Q

What are the blood groups in bovine?

A

Blood groups in Bovine
* Over 80 RBC antigens
* Yields ~2 trillion blood types
* Natural antibodies to these antigens appear to be rare
* Blood types are more often used for confirmation of
breeding/pedigree
* Large animals not commonly transfused
* Single unmatched whole blood transfusions are generally safe and
well tolerated in cattle.
* Gross crossmatch recommended for repeat transfusions

Matching done wiht hemolytic and/or agglutination test of recip. serum against RB
C of potential donors

35
Q

What is the purpose of blood typing?

A
  • to Identify specific RBC Antigen (Ag)
  • Identification of the blood group of an animal
  • i.e., specific RBC antigens in an
    animal
36
Q

What is the purpose of cross matching?

A
  • Permits identification of antibodies against erythrocyte antigens (blood groups)

Cross matching Purpose
• In vitro detection of antibodies that could lead to lysis of transfused or patient RBCs –> Helps prevent a transfusion reaction
• Anti-RBC antibodies are detected by the procedure
• Agglutinins
• RBC agglutination
• Hemolysins
• Complement-mediated RBC lysis

37
Q

Blood type does NOT detect ?

A

antibodies between patient & potential donor. Cross match IDs ab between patient and potential donors.

38
Q

What are major cross match?

A

Most important.
* Predicts if donor’s RBCs will be attacked by the recipient’s antibodies
* Washed donor RBCs are mixed
with recipient serum
* Incompatible = hemolysis or
agglutination
* Compatible = no hemolysis or
agglutination

Looking for Ab in recipient against transfused RBC antigens, m,eaning from donor, therefore we need serum form recip and RBC from donor.

39
Q

What is minor cross match?

A
  • Predicts if donor antibodies will
    attack recipient RBCs
  • Washed recipient RBCs mixed with
    donor serum
  • Incompatible = hemolysis or
    agglutination
  • Indicates prior sensitization, except in
    felines
  • Compatible = no agglutination or
    hemolysis

detects AB in donor serum to the recip RBC.
Therefore, we need serum from donor and RBC from the recip.
For test, we do another contorl, and perform to see cross matches.

40
Q

What is autocontrol?
Why do we do this?
What do we do specifically in horses?

A

Autocontrol: We also perform an auto-control with our crossmatches, i.e. recipient serum with recipient red blood cells. In these procedures, washed red blood cells are incubated with serum at 37 C (e.g. for the major crossmatch, washed donor red blood cells are incubated with recipient serum). We then look for agglutination microscopically.

In horses, we add complement (to enhance hemolysis) and look for both microscopic agglutination and grossly visible hemolysis. In horses, we also perform the test at 2 dilutions, 1:4 and 1:16.

41
Q

see below

A

In dogs and horses, naturally occurring antibody against important hemolytic red blood cell antigens (e.g. DEA 1.1 and 1.2 in the dog, and Qa and Aa in the horse) are not found. Therefore, these animals require sensitization to the red cell antigen, before a hemolytic reaction will occur.

42
Q

In cats, a crossmatch should be performed on the first blood transfusion, because cats have naturally occurring antibody to red blood cell antigens. In type B cats, the anti-A antibody is a strong agglutinin and hemolysin and can result in rapid hemolytic anemia and death if a B cat is transfused with A blood on the first transfusion. Type B cats are uncommon amongst DSH, but are found in higher frequency amongst the exotic breeds, e.g. Somali, Devon Rex

A

x

43
Q

Are there clinical studies evaluating RBC transfusions in dogs and horses?

A

There are No clinical studies evaluating an RBC transfusion threshold – or increased morbidity and mortality associated w. RBC transfusion (p 738-9 Schalm’s)

44
Q

Most cat plasma contains?

A
  • Most cat plasma contains natural anti-erythrocyte antibodies
  • First time transfusions are likely not safe
45
Q

It is assumed that all transfusions in cattle will result in ?

A

production of acquired antibodies, which may or may not be strong enough to be clinically relevant

46
Q

Mismatching leads to _________ RBC survival, as well as ___________ which will result in additional severe _________ reactions, and possible ___________ __________.

A

Mismatching leads to shortened RBC survival, as well as sensitization which will result in additional severe transfusion reactions, and possible neonatal isoerythrolysis

47
Q

Blood typing is done in ____ and ______, and _____ who are donors.
• Cross matching done ________, as well, esp if they have been ________ transfused

A

Blood typing is done in dogs and cats, and horses who are donors.
• Cross matching done routinely, as well, esp if they have been previously transfused

48
Q

How do you select a donor?

A
  • Blood-typed
  • Healthy
  • Regular vaccines
  • no RBC parasites, FeLV, FIV, EIA
  • Never transfused
  • Free of most reactive Antigens
    (species-dependent)
49
Q

Ideal dog donor?

A

Dogs:
DEA 1.1 and 1.2 negative ß ideally…

50
Q

Ideal cat donor?

A

Type A
Type B donor in certain regions

51
Q

Ideal horse donor?

A

Young gelding
Female: never transfused, or never pregnant
Lack Aa and Qa antigens (most
immunogenic)

52
Q

What are the different blood transfusion reactions?

A
53
Q

What reactions can occur due to transfusions?

A
  1. Immune-mediated hemolytic anemia
  2. Febrile & allergic reactions

Acute - immediately after transfusion. Due to blood type incompat. Type 2 hypersen. reaction. Common, particularly in dogs and horses.
Delayed - worst type –> death of animal.

54
Q

Transfusion reactions: Immune-mediated hemolytic anemia (IMHA)

  • Most common in ______, occasionally in ____
  • RBCs destroyed by ______ directed against them
  • Type ___ hypersensitivity
  • see the following in Peripheral blood smear
  • ____________
  • ________ anemia
  • _________
A
  • Most common in dogs, occasionally in cats
  • RBCs destroyed by antibodies directed against them
  • Type 2 hypersensitivity
  • see the following in Peripheral blood smear
  • Autoagglutination
  • Regenerative anemia
  • Spherocytes
55
Q

Transfusion reactions: Immune-mediated hemolytic anemia (IMHA)

Acute

A
56
Q

Transfusion reactions: Immune-mediated hemolytic anemia (IMHA)

Delayed

A

Common clinical signs: fever, anorexia, ?

57
Q

Antiglobulin (Coomb’s) testing for IMHA
Direct antiglobulin test (DAT)

A
  • Principle: detects anti-RBC antibodies or
    complement on the surface of erythrocytes
58
Q

Antiglobulin (Coomb’s) testing for IMHA
Indirect antiglobulin test

A
  • Principle: Detects anti-RBC antibodies in the serum of the patient
  • Patient’s serum is tested against washed RBCs from the sire,
    offspring, or possible blood donor animal
    The Coombs’ test has no diagnostic value in a non-anemic animal.
59
Q

What is the procedure for Coomb’s testing for IMHA?

A

Procedure
* Collect blood into an EDTA (purple top) tube
* Wash erythrocytes
* Suspend in buffered saline
* Mix with species-specific Coombs’ reagent
* Contains antiglobulins against IgG, IgM, and complement
* Incubate at 37°C for 30 minutes
* Centrifuge and check for agglutination and/or hemolysis
* Positive result means there is antibody (IgM and/or IgG), or C3 on the patient’s RBCs
–> immune-mediated component
* Can have false positive and false negative results

60
Q

What are some of the Causes of positive reactions not associated with IMHA (false positives)?

A
  • Post-transfusion
  • Cross-reactive antibodies in Coombs’ reagent
  • Bacterial or particulate contamination of Coombs’ reagent
  • In vitro complement binding during storage
  • Infections (Babesia spp., Mycoplasma spp.)
  • Neoplasia (Histiocytic Sarcoma)
61
Q

What are some of the Causes of negative reactions in animals with IMHA (false negatives)?

A
  • Concentration of antibodies on RBCs is below sensitivity of the test
  • Previous treatment with steroids
  • Elution of antibodies off RBCs

Negative result does not rule out IMHA

62
Q

Febrile & allergic reactions as a result of a blood transfusion are?

A
  • The most common Non-hemolytic reaction is an Acute hypersensitivity reaction type I. Usually do to anaphylactic or allerge type 1 hypersen. this is mediated by Ig-E mediated antibodies which activate mast cells;. Mast cells release inflammatory/vasoactive mediators –> hypotension, increase vasc. permeability, bronchiolar constriction, ? impurines?, and another reaction is an anaphylactic reaction not mediated by Ig-E.
  • Allergens in the donor blood: antibiotics, chemicals used in blood prep, albumin and complement 4.
    Rarel transfused IgE antibodies from donor can initiate reaction. This type of retio is seen in infusion of plasma eithe fresh or frozen. Cryosupernantant. Not been documented with infusion of cryopreceipitates.
  • Common w/plasma transfusion
  • 15min-few hrs
    Can occur in firs ttranfusion.
    Patient signs can occur rapidly after tranfsio9n (1 hr to 45 minutes(),.
    Minor skin reaction is the most common which is puruits facial edmea, whels, akaria, to more intense reaction such as hypotensive shocl, bronchoconstriciton, cardiopulomary arrest.
63
Q

Up to 66-75% of dogs with IHA will have a ______ Coombs test

A

positive

64
Q

A Coombs test is indicated for animals with a _________ or severe ____________ anemia, that have had other causes for the anemia (e.g. hemorrhage)
ruled out. The Coombs’ test has no ________ value in a non-anemic animal.
Many animals with other diseases (e.g. infection, neoplasia) can have a ________
Coombs test, but do not have IMHA. Therefore, a positive Coombs test in this
setting is unlikely to be clinically relevant or diagnostic.

A

A Coombs test is indicated for animals with a regenerative or severe non-
regenerative anemia, that have had other causes for the anemia (e.g. hemorrhage)
ruled out. The Coombs’ test has no diagnostic value in a non-anemic animal.
Many animals with other diseases (e.g. infection, neoplasia) can have a positive
Coombs test, but do not have IMHA. Therefore, a positive Coombs test in this
setting is unlikely to be clinically relevant or diagnostic.
38

Clinical Pathology (31 decks)

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