MLT GlobeBlood Banking: Other blood group systems – page 2
74 Blood Banking MCQs on Other blood group systems with answers and explanations.
Which maternal antibody is most likely to cause HDFN?
Anti-K is IgG and can cause severe fetal anemia. Anti-Lea, anti-P1 and anti-I are usually IgM, and the Lewis, P1 and I antigens are poorly developed on fetal red cells.
Most blood group alleles, such as Jka and Jkb or Fya and Fyb, are expressed:
Blood group alleles are codominant. A Jk(a+b+) person has inherited both alleles and expresses both antigens.
Which group of antibodies is usually IgG, reacts at 37 °C/AHG and is clinically significant?
Kell, Duffy and Kidd antibodies are usually IgG and can cause hemolytic reactions and HDFN. The other groups are mostly cold-reacting IgM antibodies.
An antigen present on the red cells of almost all people is called a:
High-prevalence antigens occur in over 99% of people. Patients with antibodies to them are hard to supply with compatible blood.
Which antibody almost never causes hemolytic disease of the fetus and newborn?
Lewis antibodies are usually IgM, which cannot cross the placenta, and Lewis antigens are poorly developed on fetal red cells. Anti-D, anti-K and anti-c are IgG and can cause severe HDFN.
A boy with chronic granulomatous disease has acanthocytes, weak Kell antigens and absent Kx antigen on his red cells. This is the:
The McLeod phenotype is X-linked (XK gene), lacks Kx, weakens Kell antigens and causes acanthocytosis; some cases have a deletion that also causes CGD. K0 cells lack Kell antigens but have increased Kx.
A patient has made anti-k (anti-Cellano). About what proportion of random donors will be k-negative?
The k antigen is high-prevalence (present in about 99.8% of people), so k-negative (K+k−) donors are rare. About 91% of people are K-negative, not k-negative.
The Kell-system antigen Js(a) is found mainly in people of which ancestry?
Js(a) occurs in about 20% of people of African descent and is almost absent in Europeans. Kp(a), by contrast, is a low-prevalence antigen found mainly in Europeans.
Besides being a red cell antigen carrier, the Duffy glycoprotein acts as a:
The Duffy glycoprotein (ACKR1, formerly DARC) binds chemokines and is the receptor used by Plasmodium vivax. The urea transporter is the Kidd glycoprotein; the water channel is Colton (aquaporin-1).
How does ficin treatment of panel cells affect reactions of anti-Jka?
Kidd antigens are resistant to proteolytic enzymes, and removing sialic acid lowers the cell charge, so anti-Jka reacts more strongly. Duffy and M/N antigens are the ones abolished.
The S and s antigens are carried on which red cell membrane protein?
S, s and U are on glycophorin B. M and N are on glycophorin A, and Gerbich antigens are on glycophorins C and D.
A multiply transfused patient of African descent has an antibody to a high-prevalence antigen. Her cells are S−s−. The most likely antibody is:
The S−s−U− phenotype occurs almost only in people of African descent, and these people can make clinically significant anti-U. Compatible blood must be U-negative, which is rare.
A person has at least one Le (FUT3) gene but is a non-secretor (se/se). The red cell Lewis phenotype is:
Without a secretor enzyme, type 1 H is not made, so Le enzyme makes only Lea. Leb needs both Le and Se genes; Le(a−b−) results when no Le gene is present.
A pregnant woman who was Le(a−b+) now types Le(a−b−) and has weak anti-Leb. The best explanation is:
In pregnancy, increased plasma volume and lipoproteins take Lewis glycolipids off red cells, so antigens weaken and transient Lewis antibodies can appear. The type returns to normal after delivery.
Anti-Lea in a patient's plasma can be neutralized in vitro by adding:
Soluble Lewis substance in saliva (or plasma) of Lewis-positive people binds anti-Lea and anti-Leb. Hydatid cyst fluid neutralizes anti-P1, not Lewis antibodies.
Which substance is used to neutralize anti-P1?
Hydatid cyst fluid and pigeon egg white contain P1-like substance that inhibits anti-P1. Human milk neutralizes anti-I, and urine neutralizes anti-Sda.
The biphasic IgG hemolysin in paroxysmal cold hemoglobinuria (Donath-Landsteiner antibody) usually has which specificity?
The Donath-Landsteiner antibody is an IgG anti-P that binds in the cold and activates complement on warming. Anti-I is the typical specificity in cold agglutinin disease.
The P antigen (globoside) serves as the cell receptor for which virus?
Parvovirus B19 enters erythroid precursors through globoside, so rare p and Pk people are resistant. EBV uses CD21 on B cells.
Which appearance is typical of Lutheran antibodies such as anti-Lua?
Lutheran antibodies classically give loose, refractile, mixed-field agglutination with small clumps among many free cells. This reflects the variable Lutheran antigen expression on individual cells.
A young adult with infectious mononucleosis develops a transient cold autoantibody. Its usual specificity is:
EBV infection is associated with a transient anti-i, which rarely causes hemolysis. Anti-I is the specificity typical of Mycoplasma pneumoniae infection.