Blood Banking Exam 2

antigen

foreign molecules that bind specifically to an antibody or a T-cell receptor (allogeneic or autologous)

hapten

small molecular weight particle that requires a carrier molecule to be recognized by the immune system

antigenic determinants/epitopes

sites on an antigen that are recognized and bound by a particular antibody or T-cell receptor

immunogen

antigen in its role of eliciting an immune response

antibody/immunoglobulin

glycoprotein that recognizes a particular epitope on an antigen and facilitates clearance of that antigen; secreted by B-cells, specifically plasma cells

IgG

antibodies that react at 37 degrees

IgM

antibodies that react at room temp or below

plasma cells

b cells that produce the majority of antibodies

memory b cells

b cells that respond rapidly to next exposure and transform into plasma cells

complement system

group of serum proteins that participate in an enzymatic cascade, ultimately generating the membrane attack complex that causes lysis of cellular elements

classical pathway

activation of complement that is initiated by antigen-antibody complexes

alternative pathway

complement that is intiated by foreign cell-surgace constituents

sensitization

antibody binds to antigen, but no visible agglutination occurs

lattice formation

antibody-coated ells cross-link to form visible agglutination

known antibody, antigen

patient cells are tested with a blank blank to identify the blank

commercial antisera

patient plasma is tested with known antisera to identify unknown antigens

anti-IgG or anti-C3d (complement), combo anti-IgG/anti-C3d

antiglobulin reagents

ABO/D

what is forward typing

patient’s red cells. commerical anti-A,, anti-B, and anti-D

what is the source of antigen in forward typing? source of antibody?

detects ABO antibodies

what is reverse testing

A1 and B cells. patient’s serum or plasma

what is the source of antigen for reverse testing? source of antibody?

RBCs with known antigens, antisera with known antibodies, antiglobulin reagents, poentiators to enhance antibodies

what are the 4 basic categories of reagents

specificity

recognition of the antigenic determinant and its corresponding antibodyp

potency

strength of the reaction

polyclonal antibodies

made from several different clones of B cells that secrete antibodies of different specificities. recognize multiple epitopes. EX. AHG

monoclonal antibodies

made from single clones of B cells that secrete antibodies of the same specificity. recongize a single epitope. ex. anti-A, anti-C, and anti-IgG antibodies

in the immediate-spin phase

when is testing performed

commericial antibody with a specificity toward human globulins is used to agglutinate antibody-coated RBCs

what is the principle of the antiglobulin test

direct antiglobulin test

detects IgG or complement bound to RBCs in vivo (IgG and complement are not normally bound to RBCs). AHG reagent is added after the RBCs have been washed

indirect antiglobulin test

detects IgG or complement bound to RBCs in vitro. two step procedure: antibodies (in serum) are incubated at 37 degrees with RBC antigens in vitro, RBC suspension is washed and then combined with AHG reagent to detecct agglutination

polyethylene glycol (PEG)

water soluble polymer suspended in a low ionic saline medium. works by removing water molecules, allowing for closer interaction of antibodies and RBC’s. used with monospecific IgG and only after the wash phase. detects some antibodies that LISS and albumin miss. does not react well with IgM antibodies. enhances warm antibodies

genes

basic units of inheritance on a chromosome

locus

the site at which a gene is located on a chromosome

alleles

alternative forms of a gene

antithetical

antigens produced by opposite alleles

polymorphic

multiple alleles at a single locus are considered

null phenotype

occurs when there is no expression of the expected red cell antigen when certain recessive alleles are inherited; homozygosity for a silent or amorphic gene

amorphic

genes that do not express a detectable product

suppressor genes

act to inhibit gene expression resulting in a null phenotype

independent segregation

occurs when one gene from each parent is passed to the offspring

independent assortment

demonstrated when blood group antigens from different chromosomes are expressed separately, resulting in a mixture of genetic material

linkage

occurs when two genes that are close to each other are inherited together

haplotype

each set of linked genes is called

linkage disequilibrium

haplotypes tend to occur at a higher frquency than unlinked genes

crossing over

occurs when two genes on the same chromosome combine and produce two new chromosomes

dosage

a variation in antigen expression due to the number of alleles present

phenotype calculation

enables finding a unit of RBCs with certain antigen characteristics

Hardy-Weinberg formula

calculates a determination of the gene frequencies that produced a trait