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RH Blood Group
RH Blood Group System
| Question | Answer |
|---|---|
| Chromosome location and gene structure of the Rh locus | Chromosome 1 |
| consists of two closely linked genes: RHD (codes for D antigen) and RHCE (codes for C and E antigens) | Rh Locus |
| Molecular difference between C/c antigen | single amino acid difference: C(Serine) vs c (Proline) at osition 103 |
| Molecular difference between E/e antigen | single amino acid difference: E(Proline) vs e (Alanine) at position 226 |
| Rh Antigens are determined by 3 pairs of closely linked genes (3 loci: D/d, C/c, E/d) inherited together as a haplotype | Fisher-Race genetic theory |
| Postulates that 1 gene on each chromosome controls total Rh expression, producing a single agglutinogen containing multiple factors | Wiener genetic theory |
| Two locus: RHD codes for RhD protein and RHCE codes for RhC and RhCE protein. RHAG on a separate loci is required for expression | Molecular theory of Rh Genes |
| Wiener shorthand for DCe | R1 |
| Wiener shorthand for DcE | R2 |
| Wiener shorthand for Dce | R0 |
| Wiener shorthand for DCE | Rz |
| Wiener shorthand for dce | r |
| Wiener shorthand for dCe | r' |
| Wiener shorthand for dcE | r" |
| Wiener shorthand for dCE | ry |
| Most common D-positive phenotype | R1r (DCe/dce) |
| Most common D-negative phenotype | rr (dce/dce) |
| Order of immunogenicity for Rh group antigens | D > c > E > C > e |
| General characteristics of Rh antibodies | IgG antibodies reacting at 37C/IAT, do not activate complement or cause extravascular destruction |
| Quantitative reduction in antigen: inheritance of an RHC gene that codes for reduced density of structurally normal D antigens on RBCs | Genetic Weak D mechanism |
| Quantitative reduction in antigen activity: steric hindrance caused when the C gene is inherited in trans position to the D gene (Dce/dCe) | Positional Effect Weak D mechanism |
| Qualitative change: RHD gene mutation causes structural alteration missing standard epitopes. Patient can produce anti-D against missing parts | D Variant (Partial D) mechanism |
| True or False D variant is determined only by indirect antiglobulin testing | True |
| D Variant patient as a blood donor: their blood is labeled as Rh - POSITIVE or Rh - NEGATIVE | Rh-POSITIVE |
| D Variant patient as a blood recipient: their blood type is labeled as Rh - POSITIVE or Rh - NEGATIVE | Rh-NEGATIVE |
| Complete absence of all Rh antigens (---/---); causes membrane abnormalities leading to stomatocytosis and compensated hemolytic anemia | Rh Null phenotype |
| epitope expressed only when c and e genes are inherited on the same chromosome in the cis position (dce or Dce) | f (ce) compound antigen |
| present on RBCs with C or D antigens, but has anti-C and anti-D activity, requires giving D-negative and C-negative blood | G antigen |
| low-frequency variant Rh antigen usually associated with C; can be naturally occurring or immune-stimulated | Cw antigen |
| Rh-associated glycoprotein resides on Chromosome 6 and is required for Rh antigen expression on the RBC membrane. | RH AG |
| Capital R = D-positive; Lowercase r = D-negative. 1 or ' = C; 2 or'' = E; 0 or plain r = neither C nor E; z or y = C and E | Fisher Race - Wiener conversion rules |
| Deletion/non-function at Cc and/or Ee loci. Displays exceptionally strong D expression but lacks C, c, E, e | D- deletion (-D- or D--) |
| The variation in antibody reaction strength depending on whether an antigen is expressed in a homozygous (stronger) or heterozygous (weaker) state on the RBC surface. | Dosage effect |
| The location of two genes on the same chromosome (e.g., c and e on dce) | Cis Position |
| The location of two genes on opposite homologous chromosomes (e.g., D on one chromosome and C on the other in Dce/dCe). | Trans Position |
| A two-stage lab technique used to detect cell-bound IgG antibodies in vitro after incubation, washing, and addition of anti-human globulin. | Indirect Antiglobulin Test (IAT) |
| mechanism of Weak D is qualitative, require special clinical handling for transfusion recipients | Partial D or D Variant |
| Most common unexpected Rh antibody in antibody screening | anti-E |
| 2nd most immunogenic; watch for concomitant anti-c when an R1R1 patient forms anti-E | c antigen |
| Associated with $G$ antigen, Cw, and trans-position Weak D effect | C antigen |
| High-frequency antigen (>98\%); most common specificity in warm autoantibodies (WAIHA) | e antigen |
| Can be immune-stimulated or naturally occurring (often appearing as a weak IgG or IgM without clear prior transfusion/pregnancy exposure) | Anti-E |
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MOrfCLS
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