Notas de internet u Para RhD Rh BLOOD

Notas de internet u Para Rh/D

Rh BLOOD GROUP SYSTEM

HISTORY u u u Ab in serum of mother of stillborn child; responsible for the death of fetus? (1939, Levine and Stetson) Rb-derived Ab to Rhesus monkey RBCs reacts with 85% of human subjects; same Ab as reported by Levine? (1940, Landsteiner and Weiner) Erythroblastosis fetalis (HDN) linked with Anti-Rh (1941, Levine et al)

NOMENCLATURE: 4 VERSIONS u Fisher Race u Suggested 3 sets of closely linked alleles (D and d, C and c, E and e) u Each gene (except d, which is an amorph) causes production of an Ag u Inherited from parents in linked fashion as haplotypes u See Tables 6 -1 and 6 -2

NOMENCLATURE u Weiner u Multiple alleles at 1 complex locus u 1 locus encodes for production of an agglutinogen which has 3 factors (antigens or epitopes) u Abs can recognize single or multiple factors u See Table 6 -3

WEINER’S THEORY

WEINER & FISHER-RACE TERMINOLOGY

WEINER & FISHER-RACE TERMINOLOGY D=R 1 ( C) 2(E) DC Dc. E 0 (neither C or E ) Dce Z (both C & E ) DCE d= r ‘( C) ‘’ ( E ) (neither C or E ) d. Ce d c. E dce y (both C & E ) d. CE

NOMENCLATURE u Rosenfield u No genetic assumptions made u Numerical system u If listed alone, the Ag is present (Rh: 1 = D Ag) u If listed with a “-”, the Ag is not present (Rh: 1, -2, 3 = Dc. E) u If not listed, the Ag status was not determined u Adapts well to computer entry

COMMON Rh TYPES BY 3 NOMENCLATURES

NOMENCLATURE u Internatl. Soc. of Blood Transfusion u 6 digit number for each Ag specificity u First 3 indicate the blood group, eg. , 004 = Rh u Last 3 indicates the Ag specificity, eg. , 004001 = D Ag of Rh system u For recording of phenotypes, the system adopts the Rosenfield approach

Rh PHENOTYPING u Uses u Parentage testing u Predicting hemolytic disease of the newborn (HDN) u Confirmation of Rh Ab specificity u Locating compatible blood for recipients with Rh Abs u Protocol u Mix unknown RBCs with Rh antisera u Take tubes through phases (IS, heat/potentiator, AHG, CCC); record data u Use published frequencies and subject information to determine genotype

GENOTYPE FREQUENCIES u u u u Dce (R 1) dce (r) Dc. E (R 2) Dce (R 0) d. Ce (r’) dce (r”) DCE (Rz) d. CE(ry) 0. 42 0. 37 0. 14 0. 02 0. 01 <0. 01 The probability of 2 frequencies appearing together = the product of those 2 frequencies. For example, DCe/dce occurs with a frequency of 0. 42 X 0. 37 or 0. 155.

Rh ANTIGENS u u u Nonglycosylated proteins (A, B, H are CHOs) Transmembrane molecules D and CE are epitopes of proteins with 417 Aas that traverse the membrane 12 X DNA sequences of D and CE differ by only 44 base pairs; CE, Ce, cd and c. E are even more similar to D Integral part of RBC membrane (Rhnull people have mild hemolytic anemia) Density of Rh Ags on RBCs varies by phenotype (see Table 6 -7)

MODEL OF Rh PROTEIN

D ANTIGEN VARIATIONS u Weak D u Some cells require addition of AHG (IDAT) to demonstrate agglutination with Anti-D u 3 mechanisms causing weak D expression u Genetic - inheritance of D genes which result in lowered densities of D Ags on RBC membranes u C trans - position effect; the D gene is in trans to the C gene, eg. , Dce/d. Ce (C and D Ag arrangement causes steric hindrance weakening D expression) u D mosaic - 1 or more parts of the D Ag is missing; may result in production of Anti-D u People with weak D are considered Rh+ and receive Rh+ blood (except mosaics)

D ANTIGEN VARIATIONS u Enhanced D u When c and D are in double doses, eg. , c. De/c. De, (C has limiting effect on expression of D) u D-- or D. . represent partial locus deletions; usually seen in consanguinous situations

D TESTING u Anti-D reagents u Saline-based - Low protein (fewer false positives); long incubation times; cannot convert to weak D testing u Protein-based - Faster, increased frequency of false positives; requires use of Rh control tube, converts to weak D testing u Chemically modified - “Relaxed” form of Anti-D in low protein medium; few false positives; saline control performed; converts to weak D testing u Blends of m. Abs

D TESTING u Protocol u Add Anti-D to “D” tube; Rh control to “C” tube u Spin, read and record u If “D” is positive, cells are Rh positive u If “D” is negative, continue testing u Add 22% albumin and incubate for 20” at 37 o. C u Spin, read, and record u Wash 3 X in saline u Add AHG, spin, read, and record u If “D” is positive after heat/albumin or AHG cells are weak D positive; if negative, cells are Rh negative; “C” should always be negative u Add check cells to neg. tubes; spin, read & record

WEAK D Ag IN THE LAB u u u Differences from normal D expression u Quantitative (inherited weak D or position effects) u Qualitative (mosaic D; could produce Anti-D) If cells are weak D, consider the person to be Rh + u Dw not given to D negative recipients u D positives usually OK for Dw recipients u Dw mothers do not receive Rho. GAM Donors and expectant mothers should be tested for weak D; transfusion recipiencts +/- for weak D testing (Dw people may receive D negative blood)

OTHER ALLELES AND ANTIGENS u u Weak C (Cw) u Not allelic to C and c (C and Cw usually seen together) u 2% of whites; very rare in blacks u Anti-Cw may be naturally occurring and shows dosage f (ce) u When c & e are in cis, eg. , dce/DCe u Combination Ag u Anti-f may be helpful in phenotyping

OTHER ALLELES AND ANTIGENS u Ce u When u u C and e in cis u Compound Ag u Ab helpful in phenotyping G u Always found with C-positive RBCs; usually with Dpositive cells u Anti G appears to bind to D, C, and G Many others

ALLELIC DELETIONS u u u No Cc and/or Ee epitopes u DC-, Dc-, D-E, D-u Enhanced or exalted D Ag expression Rhnull (no Rh Ag expression at all) u ---/--- (double bar rr) u Or, because of independently inherited suppressor genes u If exposed to any Rh Ags, make Abs to those and to Rh 29 (“pan” or “total” Rh) u Causes a mild hemolytic anemia Rhmod - weakened expression of all Rh Ags

Rh ANTIBODIES u u Immune Ig. G Abs (Ig. G 1 and Ig. G 3 most important) React optimally at 37 o. C or with AHG Order of immunogenicity: D>c>E>C>e Do not bind complement (RBC destruction by Rh Abs is extravascular)

Rh Abs: CLINICAL SIGNIFICANCE u u Severe HDN Severe transfusion reactions