Transfusion Science Flashcards
what is the red cell membrane composed of?
lipid, protein and a small amount of carbohydrate (glycolipids, glycoprotein)
what gives the red cell membrane a net negative charge?
the glycoproteins
what macromolecule are the ABO, Lewis and H antigens associated with?
carbohydrate
what membrane structure are the Rh, Kelly, Duffy and Kidd antigens associated with?
glycoprotein
what chromosome is the ABO genes on?
chromosome 9
what chromosome is the Rh gene on?
chromosome 1
what blood group system has the most antigen sites per red cell?
ABO
what blood group system has the least antigen sites per red cell?
Kell system
are more antigen sites present on homozygote or heterozygote individuals?
homozygote
what are antibodies?
proteins that are produced when a foreign antigenic structure is recognized by the immune system
what is an epitope?
the part of the antigen recognised by the immune system
what does the primary immune response produce?
IgM antibodies, slower
what does the secondary immune response produce?
IgG antibodies, faster
what causes the production of antibodies?
- environmental antigens- bacteria or viruses
2. rbc antigens- blood transfusion or pregnancy
what are the light chain classes?
kappa and lambda
what are the heavy chain classes?
mu, gamma, alpha, delta, epsilon
what part of the antibody anchors it to the surface of cells?
the constant regions
what Ig can cross the placenta?
IgG
How is the diversity of the immune system acheived?
by genetic recombination
what is K the affinity constant?
a measure of the sum of variety of weak non covalent interactions between the antigen and antibody
what forces enable antigen antibody binding
Ionic, van der Waals, Hydrogen, hydrophobic bonds
what are the stages in haemagglutination?
sensitisation: antibodies attach to antigen
agglutination: intracellular bridges form a lattice of adjacent cells
what factors affect sensitsation?
temperature, incubation time, ionic strength, pH
what are the cold reacting antibodies?
ABO, Lewis
what are the warm reacting antibodies?
Rh, Kell, Duffy and Kidd
what does lowering the ionic strength of a medium do?
speeds up the rate of association between antibody and antigen and increasing K value
what factors affect in vitro agglutination?
electrical charge, characteristics of antibody, proximity of cells, location of antigen sites, concentration of antibody
what is zeta potential?
the difference in potential expressed at the boundary of shear (edge of electron cloud)
what charge are red cells?
negative due to sialic acid residues
what does high zeta potential do?
prevents agglutination
what neutralizes the red cell charge?
papain, trypsin, bromelin, ficin
causes of agglutination
centrifugation, proteolytic enzymes, polymers, AHG
what causes direct agglutination?
IgM antibodies are large enough to span the gap between cells - ABO blood grouping
what causes indirect agglutination?
IgG antibodies, require AHG or enzymes to bridge the gap as IgG is too small
who described the first ABO blood group system?
Karl Landsteiner in 1901
are ABO antibodies IgM or IgG?
IgM
how do the ABO antibodies cause intravascular hemolysis of incompatible cells?
complement activation
where is the ABO locus on genes?
chromosome 9
where is the H and Se locus on genes?
chromosome 19
what does a-2-fucosyltransferase do?
converts a precursor oligosaccharide chain by the addition of fucose to H antigen
will a homozygous h allele form the H antigen?
no - doesnt encode transferase
what do the H,A,B genes encode for the production of?
transferase enzymes
what blood type has the most H antigen present?
O
is H antigen present on bombay cells?
no
what is the difference between A1 and A2 individuals?
A1 and A1B have more antigen sites than A2/A2B
A1 has A and A1 antigen, A2 only A
what antibodies does bombay individuals have in serum?
antiA, antiB and anti H
what stimulates ABO antibodies?
environmental antigens - bacteria and viruses
when do ABO antibodies form?
3-6 months after birth
when are ABH antigens expressed weakly?
patients with leukaemia
when does group A individual acquire B antigen?
with gastrointestinal cancer and bacterial infections
