MLT GlobeBlood Banking: Other blood group systems
74 Blood Banking MCQs on Other blood group systems with answers and explanations.
Red cells lacking which blood group antigens (Fy(a−b−)) resist invasion by Plasmodium vivax?
P. vivax uses the Duffy glycoprotein (DARC) as its receptor; the Fy(a−b−) phenotype, common in West Africans, confers resistance.
Lewis system antibodies are characteristically:
Anti-Lea and anti-Leb are usually naturally occurring IgM cold agglutinins and rarely cause haemolytic disease of the newborn.
Treating red cells with dithiothreitol (DTT) destroys antigens of which blood group system?
Kell antigens depend on disulfide bonds in the Kell glycoprotein, which DTT reduces. Kidd antigens are resistant to DTT and are actually enhanced by proteolytic enzymes.
Anti-Fya is best described as:
Anti-Fya is an immune IgG antibody detected by the indirect antiglobulin test and can cause hemolytic transfusion reactions and mild HDFN. Ficin destroys Fya, so reactions are lost, not enhanced.
The Kidd glycoprotein functions in the red cell membrane as a:
Kidd antigens are on the urea transporter (SLC14A1), which helps red cells keep osmotic stability in the renal medulla. The anion exchanger (band 3) carries the Diego antigens.
Lewis antigens on red cells are:
Lewis antigens are made in tissues and taken up passively onto red cells from plasma. This is why the Lewis type can change, e.g. in pregnancy. Non-secretors with a Le gene still express Lea.
A healthy newborn's red cells usually type as:
Lewis antigens are poorly developed at birth, so most cord cells type Le(a−b−). The adult phenotype develops over the first years of life.
Compared with adult red cells, umbilical cord red cells are rich in:
Cord cells carry mainly linear chains (i antigen); branching into I occurs over about 18 months. Adults are therefore I-positive with very little i.
Apart from D, which red cell antigen is the most likely to cause alloimmunization after transfusion?
K is highly immunogenic, second only to D among non-ABO antigens. Many transfusion services therefore give K-negative red cells to girls and women of childbearing age.
Anti-S is typically:
Anti-S and anti-s are usually IgG, react at the antiglobulin phase and can cause transfusion reactions and HDFN. This contrasts with anti-M and anti-N, which are usually cold IgM.
About what proportion of donors of European descent are K-negative?
About 9% of Europeans are K-positive, so K-negative units are easy to find. About 99.8% are k-positive.
The M and N antigens are carried on:
M and N differ at amino acids 1 and 5 of glycophorin A. S and s are on glycophorin B.
The Leb antigen on gastric mucosa is a binding site for:
H. pylori attaches to Leb on gastric epithelium. P. vivax uses Duffy and parvovirus B19 uses the P antigen.
A young adult with atypical pneumonia develops cold agglutinin hemolysis. The autoantibody usually has which specificity?
Mycoplasma pneumoniae infection is associated with transient anti-I. Anti-i is linked to infectious mononucleosis.
Diego antigens are carried on:
Diego antigens, including Dia/Dib and Wra/Wrb, are on band 3. Aquaporin-1 carries Colton antigens.
Anti-Vel is clinically important because it:
Vel is a high-prevalence antigen; anti-Vel is often IgM and IgG, binds complement and can cause severe intravascular hemolysis.
Which group of antibodies is usually IgM, reacts best at room temperature or below, and is rarely clinically significant?
Lewis, P1 and M antibodies are usually cold-reactive IgM. Kell, Duffy, Kidd, Rh and S/s/U antibodies are usually IgG and significant.
Anti-K is most often of which immunoglobulin class?
Anti-K is usually an IgG immune antibody detected at the AHG phase. It can cause hemolytic transfusion reactions and HDFN.
The antigens Jka and Jkb belong to which blood group system?
Jka and Jkb are the Kidd antigens. Kidd antibodies are known for causing delayed hemolytic transfusion reactions.
A patient has anti-Fyb. To which blood group system does this antibody belong?
Fya and Fyb are Duffy antigens, so anti-Fyb is a Duffy antibody. Duffy antigens are destroyed by enzymes such as ficin.