UCSF: Antigens, Antibodies, and Genes Flashcards
Blood groups with co-dominant genes
ABO Rh (Cc and Ee) MNS Kell Lutheran
Clinically Significant antibodies
Ss, Kell (Kk, Jsa, Jsb, Kpa, Kpb), Rh (DCEce), Lutheran (Lub), Duffy (Fya, Fyb), and Kidd (Jka, Jkb) antigens
Lewis is significant if they cause hemolysis in-vitro
Antigens Destroyed and Enhanced by Enzyme Treatment
Destroy: Duffy (Fya, Fyb) and MNS
Enhance: Rh, Kidd, P1, Lewis, and I antigens
Kell Group Systems
Clinically Significant: K, k, Jsa, Jsb, Kpa,Kpb
Other Kell: KEL11-27
Lab Results for Bombay Phenotype Patients
They will forward type as an O, but reverse type as an AB. They have no H antigen, and will have a negative reaction with Ulex europeus lectin.
Definition/Cause of Blood Type Subgroups
Blood group subtypes have fewer copies of their respective antigens than do the most common type, i.e. A1 has more copies of the A antigen than A2 cells. This results in weaker reactions in the forward typing, and may cause typing discrepancies in the reverse by forming antibodies against the other subgroups. The A1 subgroup can be distinguished by testing the sample with Dolichos biflorus lectin, which will only agglutinate A1 cells.
Characteristics of Blood Groups that cause Delayed Hemolytic Transfusion Reactions
They produce IgG antibodies, and require previous sensitization to the antigen so that upon secondary exposure, the antibodies will slowly remove the RBCs extravascularly.
Ulex europeus and Dolichos biflorus lectins
Ulex europeus lectin: produces anti-H which can help determine if there is a possible Bombay phenotype, Bombay cells will not react with this lectin.
Dolichos biflorus lectin: produces anti-A1 and is used to differentiate A subgroups by agglutinating A1 but not A2.
B(A) phenotype
A B phenotype with a small amount of A antigens on the surface. It is thought that the closely related A and B transferases are the cause of this phenomenon.
What is the major phenotype of Duffy blood group for African-Americans?
Fy3 which is Fy(a-b-)
P1 Antigen Characteristics
P antigens are synthesized by sequential action of glycosyltransferases, which add sugars to precursor substances. The precursor of P1 can also be glycosylated to type 2H chains, which carry ABH antigens.
P1, P, or Pk may be found on RBCs, lymphocytes, granulocytes, and monocytes; P can be found on platelets, epithelial cells, and fibroblasts.
P1 is found on early fetal RBCs, but their strength weakens as gestation continues.
What does “dosage effect” mean?
A phenomenon where an antibody reacts more strongly with a RBC with homozygous inheritance (carrying a double dose) than with a RBC with heterozygous inheritance (carrying a single dose) of an antigen.
What is f antigen?
A compound antigen that is caused by inheriting c and e in the same haplotype, and producing a cis product.
K Antigen Characteristics
The K antigen is extremely immunogenic, following ABO and D antigens. However it is not common, with over 90% in most racial groups lacking the antigen so the risk of a K- patient being transfused with a K+ unit is low.
Rhogam: mechanism, effectiveness of vial, quantitative analysis, who can receive Rhogam?
Rhogam is Rh immune globulin that is administered to Rh- mothers of Rh+ babies. The RhIg bonds to any fetal cells in the mother and removes them via macrophages before the mother can make her own antibodies to the fetal cells. One vial can protect against 30mL of fetal whole blood. If the fetomaternal hemorrhage test is positive, a quantification (Kleihauer-Betke) must be done to determine the number of vials that should be administered.
Patients who have already developed anti-D are not candidates for Rhogam.
What frequency does the DCe/dce genotype have in the white population?
31.1%, a high frequency genotype
In what population is Xg^a more commonly found?
In women,mad it resides on the X chromosome
What are the 3 most common non-red cell stimulated antibodies?
Anti-P1, anti-Le^a, and anti-I
What has been shown to cause an anaphylactic reaction in recipients?
IgA, in those patients who have a genetic deficiency of IgA
S/s and M/N are associated with which substances?
S/s: Glycophorin B
M/N: Glycophorin A
What is a “silent gene”?
A functional gene that is simply not expressed
What test is NOT regularly done on donor units in the United States?
HBsAg
What types of screens for HIV are done at blood centers?
Nucleic acid testing, PCR
Antigen detection: P 24
Anti-HIV1 and anti-HIV2
What effect will a bacterial infection have on serum?
The serum will have a greenish tinge
Where are the Lewis antigens produced?
On tissue cells
What are Lewis antigens classified as in secretions, plasma, and RBCs?
In secretions they are considered glycoproteins, in plasma and on RBCs they are considered glycolipids
What type of antibodies are Lewis, and do they cause HDN?
IgM, which are naturally occurring, and do not cause HDN
Characteristics of M/N antigens
Well developed at birth, susceptible to enzymes, generally saline reactive
