exam 4: tissue graft & transfusions

Question 1

what are the four different types of tissue grafts and their immune responses

Answer 1

1. autograft - animals own tissue; no rejection
2. syngenic graft - genetically identical animals; no rejection
3. xenograft - grafts from different species; rejection
4. allogenic graft - unrelated animals of same species; rejection

Question 2

what is the difference between a graft disease and host disease

Answer 2

graft: immune response to alloantigens in the graft
host: donor T cells are activated by recipient APCs & attack recipient cells

Question 3

how does the body tolerate fetal tissue?

Answer 3

1. placental sequestration
2. local factors
3. systemic factors

Question 4

what is placental sequestration?

Answer 4

fetal derived tissue that…
-does not express MHC II
-restricted MHC I expression,
- indolemaine 2,3-dioxygenase (IDO) production to dampen Th1 response
- regulatory cytokine production (Treg) to minimize fetus rejection

Question 5

what are local factors to tolerate fetal tissue

Answer 5

uterine entrapment of APC
chemokine gene silencing by decidual stromal cells

Question 6

what are systemic factors to tolerate fetal tissue

Answer 6

-expansion of maternal Treg cells with fetal specificity
-release of tolerogenic placental debris into maternal circulation
-immune modulation by progesterone and its downstream factors

Question 7

what type of immunity predominates during pregnancy?

Answer 7

Th2

Question 8

what is a type II hypersensitivity reaction due to blood transfusion

Answer 8

type II hypersensitivity reactions due to antibodies binding RBC proteins = complement activation, phagocytosis of RBC, and direct lysis

Question 9

what is an alloimmune reaction due to blood transfusion

Answer 9

alloimmune: antibody from another member of the species binds antigen on affected patients RBC; could be due to mismatched blood transfusion or neonatal isoerythrolysis

Question 10

what is a primary transfusion reaction

Answer 10

primary: patients antibody binds the patient’s self RBC antigen

Question 11

what is a secondary transfusion reaction

Answer 11

secondary: patients antibody binds absorbed antigen on RBC

Question 12

what are types of RBC antigens

Answer 12

glycoproteins, receptors, transport proteins, structural proteins, absorbed factors

Question 13

in most species, does the primary or secondary immune response more likely to cause damage, why?

what species are the exception?

Answer 13

secondary immune response is more likely to cause damage because antibodies are formed after exposure to antigen

cats & humans are the exceptions because their antibodies are strong enough to cause damage the first time

Question 14

what clinical signs may be observed during a transfusion reaction

Answer 14

pale mucous membranes
icterus
apnea
tachycardia
lethargy

Question 15

what are the major blood groups in equine?

what antigens are of importance for isoerythrolysis?

what naturally occuring antibodies can horses have? is this rare?

Answer 15

7 blood groups = ACDKPQU

Aa & Qa are of importance for neonatal isoerythrolysis

anti-Aa & anti-Ca are rare, naturally occuring antibodies

Question 16

describe neonatal isoerythrolysis in equine

Answer 16

-forms during blood exchange at birth
- negative Aa/Qa mares, positive Aa/Qa foals
-usually occurs with mares second foal, not the first
-colostrum with maternal antibodies will target paternal antigen present in foal causing hemolysis

Question 17

what are naturally occurring antibodies in canines? what do they do?

Answer 17

DEA-3, DEA-5, DEA-7
these naturally occuring antibodies cause increased RBC removal during the first transfusion

Question 18

what causes neonatal isoerythrolysis in canines? why is this important in 2nd transfusions?

Answer 18

DEA-1
will cause severe hemolysis in 2nd transfusions

Question 19

which blood groups can cause severe hemolysis in 2nd transfusions in canines

Answer 19

DEA-1 & Dal

Question 20

what blood group for canines is a good donor

Answer 20

DEA-4

Question 21

what are feline blood groups? which ones are common or rare

Answer 21

type A (genetically A/A or A/B) common
type B (genetically B/B) rare
type AB (genetically A/A or A/B but have second gene that modifies some A into B so both are expressed on RBC) extremely rare

Question 22

what antigen is unique to felines

Answer 22

the Mik antigen

Question 23

what causes severe transfusion reactions in felines

Answer 23

A+ blood to B+ cats
mik+ blood to mik- cats

Question 24

what are the naturally occuring antibodies in felines? what do each of them cause?

Answer 24

anti-A –> severe hemolysis
anti-B –> increased RBC removal during first transfusion of mismatched blood
anti-Mik –> hemolysis

Question 25

what causes neonatal isoerythrolysis in felines? what can this cause

Answer 25

type B queens (they have anti-A Ab) mate with a type A tom and have type A/B or AB kittens

late term abortion

Question 26

what test can be used to prevent transfusion reactions in dogs and cats

Answer 26

blood typing to screen for major antigens on RBC and avoid giving blood to different type:
dogs test for DEA-1
cats test of A,B or AB blood type

Question 27

what is cross-matching?

Answer 27

determines if there are any antibody:antigen interactions

Question 28

what is a major cross match?

Answer 28

1 drop donor RBC + 2 drops patient serum
patient Ab against donor RBC (problem)

Question 29

what is a minor cross match?

Answer 29

1 drop patient RBC + 2 drops donor serum
donor Ab against patient RBC

Question 30

what will mismatched blood samples result in?

Answer 30

agglutination or hemolyze

Question 31

when should transfusions be performed?

Answer 31

only when necessary for patient survival…PCV < 10-15% or 50% acute decrease in PCV