4. Rh Blood Group System

Comprehensive flashcards covering the Rh blood group system lecture, including antigen inheritance theories, Fisher-Race, Wiener, Rosenfield, and ISBT nomenclatures, clinical significance, dosage, and antibody development.

Why is the Rh blood group system considered the second most important system after ABO?

ABO is the most important because it is the quickest way to kill someone, while Rh antibodies are clinically significant $IgG$ antibodies that can cause severe transfusion reactions and hemolytic disease of the fetus.

What are the five key antigens belonging to the Rh blood group system?

Big $D$, little $c$, big $C$, little $e$, and big $E$.

How should a lowercase 'c' antigen be written on tests to distinguish it from a capital 'C'?

With a line drawn over the little $c$ ($\bar{c}$).

Has a 'little d' antigen ever been identified or found?

No, a little $d$ antigen has never been found; the letter $d$ is merely used as a placeholder representing the absence of the big $D$ antigen.

How is Rh positive or Rh negative status determined in routine testing?

It depends on reactivity with anti-$D$ antiserum: agglutination indicates Rh positive, whereas no agglutination indicates Rh negative.

What are the only two ways an individual can be exposed to Rh antigens to produce Rh antibodies?

Through pregnancy or through blood transfusion.

What percentage of Rh-negative individuals exposed to Rh-positive red blood cells will develop anti-$D$?

$50\%$ to $70\%$ (or sometimes even higher).

What type of blood is selected for intrauterine transfusions in a fetus affected by maternal anti-$D$?

O-negative red blood cells that are less than $7$ days old and hemoglobin negative.

What did Karl Landsteiner and Alexander Wiener discover when they injected guinea pigs and rabbits with rhesus monkey red cells?

They discovered an antibody that agglutinated human red cells, which led to the discovery of the Rh system; the animal antibody was named anti-LW (Landsteiner-Wiener), whereas the human antibody is anti-Rh.

What is the currently accepted genetic model for Rh inheritance proposed by Tippett in $1993$?

Two closely linked genes on chromosome $1$: the $RHD$ gene encoding the $D$ antigen, and the $RHCE$ gene encoding the $C$, $c$, $E$, and $e$ antigens.

What are the approximate population frequencies of the five principal Rh antigens?

$D$: $85\%$, big $C$: $70\%$, big $E$: $30\%$, little $c$: $80\%$, and little $e$: $98\%$.

Why does the $D$ antigen not demonstrate dosage like the $C$, $c$, $E$, and $e$ antigens do?

Because there is no measurable 'little d' antigen to compare expression against, making true phenotypic dosage impossible to detect without molecular DNA testing.

How did the Fisher-Race theory propose Rh antigens were inherited?

As three closely linked sets of alleles at three loci ($D/d$, $C/c$, and $E/e$) inherited together as a haplotype.

In Wiener nomenclature, what do a capital 'R' and a lowercase 'r' indicate?

A capital '$R$' indicates the presence of the big $D$ antigen, whereas a lowercase '$r$' indicates the absence of the big $D$ antigen.

What do the numbers '$1$' and '$2$' represent in Wiener uppercase nomenclature ($R_1$, $R_2$)?

'$1$' indicates the presence of the big $C$ antigen ($R_1 = D, C, e$), while '$2$' indicates the presence of the big $E$ antigen ($R_2 = D, c, E$).

What antigen combinations are represented by Wiener's $R_0$ and $R_z$?

$R_0$ represents $D, c, e$ (only $D$ is dominant/capitalized), and $R_z$ represents $D, C, E$ (all three antigens are dominant/capitalized).

In Wiener nomenclature, how are lowercase alleles with big $C$ or big $E$ designated?

A single prime ($'$) represents big $C$ (e.g., $r' = d, C, e$), a double prime ($''$) represents big $E$ (e.g., $r'' = d, c, E$), and $r^y$ represents both big $C$ and big $E$ ($d, C, E$).

What are the most common Rh-positive and Rh-negative genotypes?

The most common Rh-positive genotype is $R_1r$ ($DCe/dce$), and the most common Rh-negative genotype is $rr$ ($dce/dce$).

What numerical designations correspond to the five major Rh antigens in the Rosenfield system?

$\text{Rh1} = D$, $\text{Rh2} = C$, $\text{Rh3} = E$, $\text{Rh4} = c$, and $\text{Rh5} = e$.

How is a red blood cell phenotype positive for $D$, $C$, $c$, and $e$, but negative for $E$, written in Rosenfield nomenclature?

$$\text{Rh:1,2,-3,4,5}$$

What is the three-digit blood group collection number assigned to the Rh system by the ISBT?

$$004$$

If a patient has the phenotype $d, c, E, e$ ($r r''$), what unexpected Rh antibodies can they form upon exposure to Rh-positive blood?

They can produce anti-$D$ and anti-$C$, because they lack both the $D$ and big $C$ antigens.