BB Final Exam Review

Describe the three mechanisms that result in weakened expression of the D antigen.

Describe the three mechanisms that result in weakened expression of the D antigen.

1. Position Effect: C in Trans to D; C is on opposite haplotype from D-steric arrangement (C interferes w/ D expression)

2. Weak D: Quantitative changes due to fewer D antigen sites

3. Partial D or D Mosaic: D Ag expression weakened when ≥1 D epitopes w/i the entire D protein is missing or altered. (possibility of making anti-D)

Direct Antiglobulin Testing detects in (vivo/vitro) sensitization of RBCs.

in vivo (body)

Indirect Antiglobulin Testing detects in (vivo/vitro) sensitization of RBCs.

in vitro (tube)

What is the purpose of cross-matching?

Determines compatibility of donor RBCs with recipient’s blood. (Ag’s on the donor cells, Ab on the patient serum/plasma)

What is the purpose of running an autocontrol? What does an autocontrol consist of?

1. Used to detect autoantibodies or DAT + cells

2. Patient’s serum/plasma + Patient’s own RBCs

What is the point of the “wash step” during IAT and DAT?

To remove any unbound antibodies that have the possibility of neutralizing the AHG and causing a false-negative reaction.

You just added check cells to your negative AHG reactions and they agglutinated. What does this tell us?

1. The test was adequately washed prior to addition of the AHG reagent.

2. AHG reagent was added to the test tube.

3. The AHG reagent that was added was in an ACTIVE form.

You just added check cells to your negative AHG reactions and they did NOT agglutinate. What does this tell us?

• You may have forgotten to add AHG

• Your results are invalid

• Repeat the procedure with new AHG reagent and check the cell washer

When would you perform an Extended Crossmatch?

1. Patient history

2. At least one positive screen cell

• No history of antibodies

• SC+

Extended XM or Immediate Spin (IS) XM?

Extended crossmatch

• History of Anti-K

• SC=

Extended XM or Immediate Spin (IS) XM?

Extended crossmatch

• No history of antibodies

• SC=

Extended XM or Immediate Spin (IS) XM?

Immediate Spin (IS) XM

Given:

Lele sese Hh AO

1. What is the RBC phenotype?

2. What Antigen(s) would be secreted?

1. H, A, Lea+

2. Lea

Given:

Lele Sese Hh BB

1. What is the RBC phenotype?

2. What Antigen(s) would be secreted?

1. H, B, Le(a-b+)

2. H, B, Lea, Leb

Given:

Hh or HH, Sese or SeSe, lele

1. What is the RBC phenotype?

2. What Antigen(s) would be secreted?

1. H, Le(a-b-)

2. H

Given:

Lele sese hh

1. What is the RBC phenotype?

2. What Antigen(s) would be secreted?

1. Le(a+b-)

2. Lea

Given:

lele sese AO or AA Hh

1. What is the RBC phenotype?

2. What Antigen(s) would be secreted?

1. A, H, Le(a-b-)

2. none

Secretor Study

saliva + anti-A + commercial A-cells → agglutination (+ test)

What is your interpretation?

• No soluble A antigen present in saliva

• saliva is from a non-secretor of ABH

Secretor Study

saliva + anti-A + commercial A-cells → NO agglutination (= test)

What is your interpretation?

• soluble A antigen present in saliva

• saliva is from a secretor of ABH

What anticoagulant is preferred for DAT?

EDTA

What are some possible causes of a positive DAT?

• Autoimmune HA

• HDN

• Drug-related

• Transfusion reaction

• Infusion of incompatible unit

What is the most common elution method used today?

Glycine acid

What are some drawbacks/cons of the xylene elution method?

• Flammable

• Carcinogenic

• Need to use in a ventilated area (hood)

What is an elution method best suited for eluting ABO antibodies?

Lui-Freeze Thaw

Which antibody class can cross the placenta? (IgG or IgM)

IgG

Rh antibodies belong to which antibody class?

IgG

What is the optimal reaction temperature for Rh antibodies?

37 C

Which blood groups show dosage on an ABID panel?

1. Rh

2. Duffy

3. Kidd

4. MNS

What phase does Rh antibodies react act?

AHG

What is Rhogam (RhIg)?

It’s a concentrate of predominantly IgG anti-D (RhIg) developed from pools of human plasma.

How does Rhogam work?

• Prevents mom from making immune anti-d by suppression of immune response.

• RhIg attaches to positive fetal red cells activating suppressor T-cells (current theory)

When do you give Rhogam?

• Antenatal administration: Given at 28 (to 32) weeks gestation to Rh negative pregnant women as long as the antibody screen is negative for anti-D.

• Amniocentesis: When an amniocentesis is preformed (16-18 weeks gestation) should receive full dose.

• Postpartum administration: When mom is Rh negative and has not produced anti-D and baby is Rh positive. Given w/i 72 hrs of delivery.

When do we run a weak D?

1. Obstetric patient

2. Donor units

How is weak D run?

1. Perform Rh typing on sample

2. Perform Weak D testing on Rh negative samples (of donor units or obstetric pt)

3. Incubate tube (Anti-D + patient cells[same tube from your Anti-D typing]) at 37 C for 15-30 min

4. After incubation, wash 3-4x in cell-washer

5. Add 2 drops of AHG reagent

6. Spin/read

What do you do next when a weak D test is positive? Why?

Run DAT because you want to make sure that the reaction is a valid reaction and not just due to the red cells being coated by an antibody.

What antibody class does the Kell blood group belong to?

IgG

What is the optimal reaction temperature for Kell?

37 C

What phase will Kell react at?

AHG

K is highly immunogenic and often associated with DHTR. (True/False)

True

What are the antigen frequencies for K and k respectively?

1. 9%

2. 91%

Kell null cells can be made with treatment by _____ , _____ or ______.

2-ME, DTT or ZZAP

What phenotype is resistant to malaria?

Fya-b-

Duffy blood group is destroyed by enzyme treatment. (True/False)

True

What are the antigen frequencies for Fya and Fyb respectively?

1. 65%

2. 80%

What antibody class does the Kidd blood group belong to?

IgG

What is the optimal temperature that Kidd will react at?

37 C

What phase will Kidd react act?

AHG

What effect does enzyme treatment have of Kidd antibodies?

Enhanced by enzymes

What does Anti-Jk3 mean?

Patient will be Jka-b-

What are the frequencies for Jka and Jkb respectively?

1. 77%

2. 72%

Why are Kidd antibodies implicated in delayed transfusion reactions?

Titer drops below detectable levels very quickly

What are some diseases associated with Kell?

1. McLeod Phenotype (decreased RBC survival)

2. Chronic Granulomatous Disease

What antibody class does Lewis blood group belong to?

IgM

What is the optimal reaction temperature for Lewis?

Most often 4 C, sometimes 37 C

If Lewis is reactive at room temperature, it is clinically significant. (True/False)

False

What phase does Lewis react at?

RT, 37 C, and AHG

What effect does enzyme treatment have on Lewis antibodies?

Enhanced by enzymes

Lewis can be neutralized. (Treu/False)

True (saliva)

Why is Lewis not implicated in HDFN?

Lewis antigens are poorly developed at birth (cord cells are Lea-b-)

What are the frequencies of Lea and Leb respectively?

1. 22%

2. 72%

What antibody class do MN belong to?

IgM

What antibody class does S belong to?

IgG

What is the optimal reaction temperature for MN?

4 C or 37 C

What phase does MN react at?

IS, 37 C, and AHG

What effect does enzyme treatment have on MN?

Destroyed by enzymes

What can be done to enhance Anti-M reaction?

Acidify pH

What is the optimal reaction temperature for S?

37 C

What phase does S react at?

AHG

What effect does enzyme treatment have on S?

variable

Is S blood group clinically significant?

Yes

What are the frequencies for M, N, S and s respectively?

1. 79%

2. 70%

3. 55%

4. 90%

List the IgM antibodies

1. anti-I, -H

2. anti-M

3. anti-N

4. anti-P1

5. anti-Lea

6. anti-Leb

What are the IgG (clinically significant) antibodies?

1. anti-D

2. anti-C, -c

3. anti-E, -e

4. anti-M (some)

5. anti-K, -k

6. anti-Fya, -Fyb

7. anti-Jka, -Jkb

8. anti-S, -s

What antibody class does P blood group belong to?

IgM (Anti-P1)

What is the optimal reaction temperature for P?

4 C

What phase does P react at?

IS, 37 C, AHG

What effect does enzyme treatment have on P?

Enhanced by enzymes

Anti-P1 can be neutralized by ______.

Hydated cyst fluid

Is Anti-P1 clinically significant?

No

Donath-Landsteiner antibody

Autoanti-P

What antibody class does Ii blood group belong to?

IgM

What is the optimal reaction temperature for Ii?

4 C

What phase does Ii react at?

IS and occasionally 37 C

What effect does enzyme treatment have on Ii antigens?

Enhanced by enzymes

Ii is not clinically significant. (True/Fasle)

True

A strong Anti-I reaction is associated with which bacteria?

Mycoplasma pneumonia

Anti-i is associated with which disease?

Infectious mononucleosis

ABID rule out instructions

1. Match anagram to panel by lot #

2. Use only cells that have a negative reaction

3. Dosage: use a homozygous cell only

4. Rule of 3

If a patient has an antibody to a high incidence antigen and needs some blood, where would they find it?

• Sibling

• Rare donor file

What is a high incidence antigen?

Antigens that occur in greater than 99% of the population.

If a patient has an antibody to a low incidence antigen and needs some blood, where would they find it?

Random donors

What is a low incidence antigen?

These antigens occur in less than 1% of the population.

What is the purpose of phenotyping?

To confirm the antibody that was found

What is the equation for screening units?

(# of Units Requested)/(frequency of Antigen negative in population)

ABO Discrepancy

Weak/Missing Antibody (isoagglutinin)

• What are the causes of this discrepancy?

• Elderly

• Newborn

• Immunosuppressed (Leukemia, Hypogammaglobulinemia)

• BMT

• Congenital immunodeficiencies

ABO Discrepancy

Weak/Missing Antibody (isoagglutinin)

• How would you resolve this discrepancy?

• Incubate @ RT for 30 min.

• Incubate @ 4 C for 30 min.

• Adsorption/Elution

ABO Discrepancy

Weak/Missing antigen

• What are the causes of this discrepancy?

• Subgroup of A or B

• Disease state (leukemia)

• BMT

ABO Discrepancy

Weak/Missing antigen

• How would you resolve this discrepancy?

• Incubate @ RT for 30 min.

• Incubate @ 4 C for 30 min.

• Adsorption/Elution

ABO Discrepancy

A B D interp A1 cells B cells interp

4 0 4 A pos 1 4 O

Extra reaction in the reverse

• What are the causes of this discrepancy?

• Subgroup of A

• Cold Alloantibody

• Cold Autoantibody

ABO Discrepancy

Extra reaction in the reverse

• What is run next to determine the cause?

1. O cells

2. A2 cells

3. Autocontrol (pt plamsa + pt RBCs)