blood bank exam 1 part 1

define a blood group system

antigens (proteins, glycoproteins) that are produced by alleles at a single genetic locus that are closely linked

How is a gene expressed and how is the blood group system gene expressed to make the antigen? FIRST possibility

the gene codes for a transmembrane protein that is directly formed when expressed

How is a gene expressed and how is the blood group system gene expressed to make the antigen? SECOND possibility

the genes codes for a glycosyltransferase enzyme that adds a carbohydrate to a RBC membrane precursor substance

define cis inheritance

alleles on the same chromosome

define trans inheritance

alleles on opposite chromosomes

define co dominant

2 genes are both expressed, rather than 1 over the other

A and B alleles are this

define Recessive

only expressed if both copies are inherited from both parents, dominant alleles mask this trait from being inherited

O is this

define Dominant

expressed if 1 copy of a gene is inherited, masks recessive allele

define Amorph

loss of function mutation, produces non functional allele, the trait shows expression

O is this = no gene product

What are the ingredients for performing any blood typing serological procedure

3-5% suspension, anti A, anti B, anti D for forward typing

plasma, a cells, b cells = reverse typing

Name of net negative charge around the red cells

zeta potential

0

no agglutination, free flowing cells

1+

small clumps or cells, cloudy background

2+

medium and small clumps of cells, background may be cloudy

3+

large clump of cells plus some small clumps, clear background

4+

single clump of cells, clear background

forward typing

to determine what ABO antigens are present on patient RBC’s

reverse typing is to

determine what performed ABO antibodies are present in patient plasma

identify discrepancies

D typing is to

determine the presence or absence of the D antigen on patients RBCs

antibody screen/ ID is to

determine the presence of and identify any unexpected antibodies to RBC antigens

antiglobulin testing is to

check for presence of antigen-antibody sensitization that did not lead to lattice formation

forward typing reagents needed

anti A antisera

anti B antisera

reverse typing reagents needed

A cells

B cells

D typing reagents needed

Anti D

antibody screen/ ID reagents needed

group O screen and identification panel cells

antiglobulin testing reagents needed

AHG → anti human globulin

check cells → only if results are negative

what is the percent of the saline that we use to make suspensions

0.9%

why do we make a 3-5% cell suspension and not use packed cells

to standardize the source of antigens

sensitization of RBCs antigens with antibodies is best achieved when there is an optimal balance of each → more of one over the other could limit sensitization and make visualization challenging

advantages of monoclonal antibodies

unlimited production, no contaminating antibodies

disadvantages of monoclonal antibodies

antibody with single specificity may not react with all antigens because antigen may not express every epitope → can result in weaker rxn’s

specificity may be relative bc antigenic determinant may be shared with several antigens

what causes false negatives on AHG testing

inadequate washing

improper centrifugation

improper concentration of RBC

plasma not added IA

what causes false positives on AHG testing

dirty glassware

IAT (indirect antiglobulin test)

demonstrates in vitro (in a tube) reactions between RBCs and IgG antibodies

DAT (direct antiglobulin test)

detects RBCs that have been sensitized in vivo (in the body)

Performed for visualization (agglutination) of antigen-antibody reactions when present

Gel systems

Antigen-antibody reactions occurs at the top of the column, agglutinates will become trapped in gel during centrifugation, causing cloudiness

Solid systems

RBC antigens/antibodies coated to bottom of microtiter plate wells.

Agglutinates will cause diffuse RBC pattern

what does Dolichos biflorus reacts with

agglutinates with A1 cells but not A2

what does ulex europaeus react with

agglutinates with A2 cells since A1 cells have very few exposed H antigens

what phenotype does Europaeus react with

 A2 or A2B cells

what phenotypes does D. biflorous react with

A1 or A1B cells

immunodominant sugar for H antigens

L-Fucose

immunodominant sugar for A antigen

N-acetyl-D-galactosamine

immunodominant sugar for B antigen

D-galactose

Bombay phenotype

hh and se/se genotypes

lack H substance on RBCs and secretions

no antigens in secretions and no antigens on RBCs

Bombay patients make a

potent IgM antibodies against H antigen along with anti-A, anti-B and anti-A,B

Where can ABO antigens be found in the body

plasma

Landsteiners rule - summary

Normal and healthy individuals possess ABO antibodies to the ABO antigens that they don't have on their RBCs (aka the other blood types they don't have)

Thus hemolytic transfusions reactions can occur in patients who have never been exposed to blood products if incompatible ABO unit is given

what genes need to be present for A and B antigens to be expressed on red cell surfaces

functional H antigen is required and immunodominant sugar present

Landsteiners rule - true definition

Naturally occurring - non RBC stimulated. Developed due to exposure to environmental antigens that mimic out ABO antigens

immunodominant sugar for O

L-fucose

what is the precursor substance for red cell antigen production

H antigen

what is the precursor substance for secretor status

Se gene located on chromosome 19

produces L-fucosyltransferase

RBC donation:

Universal donor

O

RBC donation:

universal recipient

AB

Plasma donation

universal recipient

O

plasma donation

universal donor

AB

A blood:

RBC products

A, O

A blood

plasma products

A, AB

B blood

RBC products

B, O

B blood

Plasma products

B or AB

AB blood

RBC products

AB, A, B, O

AB type

plasma products

AB

O blood

RBC products

O

O blood

plasma products

A, B, AB, O