Rh System

Question 1

State frequency of D, C, E, c, and e Ags in the US Caucasian population

Answer 1

e+ → 98%
D+ → 85%
c+ → 80%
C+ → 70%
E+ → 30%

Question 2

Rh Ag

- Development on newborn RBCs

Answer 2

Fully developed at birth

- Reasono why HDFN is so severe

Question 3

Rh Ag

- Location in the body

Answer 3

RBC membrane ONLY, as lipoproteins (← carries antigenic specificity)

Question 4

T/F, Rh Ags are found in secretions

Answer 4

False

Question 5

T/F, Rh Ags are not located on WBCs, plts, or other tissues

Answer 5

True

Question 6

What is the most important Rh Ag?

Answer 6

D

Question 7

T/F, testing for D Ag is part of every blood type

Answer 7

True

Question 8

3 undertermined D Ags

Answer 8

• Genetic
• Position effect
• Partial D (D Mosaic)

Question 9

Genetic weak D

- Mechanism of production

Answer 9

Inheritance of D genes that code for weakened expression of D Ag (detected at AHG phase)

Question 10

Genetic weak D

- Ability oproduce anti-D

Answer 10

No

Question 11

Position effect weak D

- Mechanism of production

Answer 11

D Ag is weakened when C is “trans” to D (usually w/ r’)

Question 12

Position effect weak D

- Ability to produce anti-D

Answer 12

No

Question 13

Partial D (D Mosaic)
- Mechanism of production

Answer 13

Incomplete D Ag

Question 14

Partial D (D Mosaic)
- Ability to produce anti-D

Answer 14

Yes

Question 15

Clincial significance of Weak D phenotype

- Donors

Answer 15

Donor blood must be tested for weak D AND labeled as D+ if tested as weak D+
- D Ag, even if incomplete, can cause immune production of anti-D

Question 16

Clinical significance of Weak D phenotype

- Transfusion recipients

Answer 16

If weak D is not tested at IS, just call patient D= adn transfuse w/ D= blood

Question 17

Rhnull

- Laboratory findings

Answer 17

Lacks all Rh Ags

Question 18

What happens to RBC membranes if an individual lacks all Rh Ags?

Answer 18

RBC membrane becomes leaky allowing Na and K in and out

Question 19

Rhnull transfusion recipient can accept what blood type?

Answer 19

Rhnull RBCs only

- Often develop Abs to one or more of the Rh Ags

Question 20

Rare Rh Ags

Answer 20

• G
• Compound Ags
• Deletions/enhanced D

Question 21

G Ag

- Found where?

Answer 21

Present on most D+ and C+ RBCs

- Anti-G reacts as a combination of anti-C and anti-D adn will react when either C or D is present

Question 22

G Ag

- Who makes anti-G?

Answer 22

Individuals who are negative for both C and D (r”, r)

Question 23

Compound Ags

Answer 23

f (ce), rhi (Ce), rhii (cE)

- Abs produced will only react when BOTH Ags are in “cis” position; useful in determining MPG

Question 24

Deletions/enhanced D

Answer 24

• Lack Cc and/or Ee
• Strong D Ags (all that’s being expressed)
• Consanguineous marriage

Question 25

Rh Abs | - Ig class

Answer 25

IgG

Question 26

Rh Abs | - Stimulus for production

Answer 26

RBC stimulated (unexpected Abs)

Question 27

Rh Abs | - Ability to bind complement

Answer 27

No

Question 28

Rh Abs | - Characteristic serologic reactivity

Answer 28

- Reactivity is greatly enhanced when cells have been enzyme-treated (helpful in ABID) - Cross placenta (HDFN) - Causes HTR

Question 29

Rh Abs | - Clinical significance

Answer 29

- React best at 37C | - React best at AHG

Question 30

Rh Abs | - Transfusion practices

Answer 30

- Try to give type specific when possible - Rh= → Rh+ - Rh+ → Rh= ONLY in emergencies and patient does not already have anti-D (stop right away) - Never give Rh+ to Rh= female of child-bearing age

Question 31

Procedure for D Ag Testing

Answer 31

1. 1 drop mfg anti-D + 1 drop 5% patient cells | 2. Spin and read; if negative at IS, save tube and run Rh control AND weak D

Question 32

Procedure for Weak D Testing

Answer 32

1. add mfg anti-D or Rh control + 1 drop patient cells (ratio must match) 2. incubate 15' @ 37C 3. Wash 3x 4. Add 2 drops AHG 5. Spin and read; if positive and Rh control is negative, stop and report, if negative, continue 6. Add 1 drop CCs 7. Spin and read → should be positive

Question 33

Rh control | - Purpose of use

Answer 33

Serves as negative control for D testing - Detects interference fron unexpected Abs coating cells; at IS phase detects cold autoAbs; at AHG phase, detects pos DAT

Question 34

Rh control | - Composition

Answer 34

Diluent of anti-D w/o any Ab in it

Question 35

Rh control | - Expected results

Answer 35

Rh control must be negative for test to be valid

Question 36

Anti-D (+) Rh control (=) Interpret

Answer 36

D+

Question 37

Anti-D (=) Rh control (=) Interpret

Answer 37

D=

Question 38

Anti-D (+) Rh control (+) Interpret

Answer 38

Inconclusive

Question 39

Anti-D (=) Rh control (+) Interpret

Answer 39

Should never get this result

Question 40

Causes of invalid D typings at IS and AHG phases of testing

Answer 40

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