Blood Bank Immunology Principles & Application Flashcards
Immunology as it relates to Blood Banking
involves the immune response to transfusion of cellular elements containing antigens and/or antibodies
Immunohematology
the study of blood group antigens and antibodies
Blood Banking
originally referred to as the storage of blood and blood products for later transfusion
Transfusion Medicine
medical field that deals with the transfusion of blood and blood products
Innate Immunity Overview
includes phagocytic cells, chemical mediators, and promotion of the inflammatory system
NO MEMORY
Physiologic responses leading to inflammation
vasodilation: increased blood flow & increased temp
edema: increased capillary permeability w/ an increase in fluid
phagocyte migration into tissue
Symptoms following transfusion
most common - raised, red, itchy skin rash (urticaria)
swelling of hands, feet, arms, etc
dizziness
headaches
Acquired immunity overview
specific immune response w/ memory involving antibodies and complement etc
immunogen
any antigen that causes a detectable immune response
epitope
part of an antigen that is recognized and bound by specific antibody
haptens
low molecular weight molecules that are only antigenic when combined with a carrier
relative antigenicity
proteins > CHO > lipids /DNA
glycoproteins > CHO
lipoproteins > glycolipies > lipids
Immunogenicity
more foreign 3D structures over 10,000 daltons greater the dose intravenous > other routes of administration
Red Cell antigens
over 250
proteins (RhD), CHO (A,B) or glycolipids (P family)
Platelet Antigens
90% of platelet antibodies are to HLA proteins on the surface of platelets
10% are to platelet proteins
can cause post transfusion purpura in which the platelets are destroyed following transfusion
Relevance of IgG antibodies
IgG can cross the placenta! & can cause destruction of fetal RBC in HDNB
Anamnestic Response
also called the secondary immune response - the characteristic short lag phase that occurs within 1-2 days of exposure
bc of memory cells from primary exposure, the concentration of circulating antibody is much higher (IgGs)
RBC antibody production
depends on : person must lack the antigen immunocompetence survival of antigen in circulation antigenicity of the antigen number of antigenic exposures
‘Naturally Occuring Antibodies’
present in people not sensitized by RBC antigen exposure
produced by environmental substances that contain antigens similar to RBC antigens
Immune-Stimulated Antibodies
produced in response to exposure to specific RBC antigens through TRANSFUSION or PREGNANCY
most are IgG
most common are Rh, Kell, Duffy, Kidd, and Ss
Affinity
the binding between a single antibody and epitope of an antigen
affinity is effected by
goodness of fit (size & shape)
strength of molecular forces leading to binding
avidity
overall strength of reactions between antigen-antibody complexes
avidity is effected by
valency of antibody
affinity
Antigen-antibody reactions
high Ag & Ab drives reaction forward (form complexes)
low Ag & Ab drives the reverse reaction
when Ab is IgG - at 37 AgAb complexes are favored
when Ab is IgM - at 25 AgAb complexes are formed
hemagglutination
agglutination of RBCs to form a visible clump
antibodies bind to antigens on RBC surface
0, +/-, 1+,2+,3+.4+
RBC hemolysis
occurs when complement is activated, membrane is damaged, intracellular fluid is released & supernatant becomes red
Sensitization phase
first stage of in vitro antibody antigen binding usually not visible influenced by : cell: serum ratio temp incubation time pH & ionic strength
Effect of Temperature
cold antibody vs warm antibody
effect of pH
6.5-7.5 is usually best some antibodies (anti-M) react better in more acidic pH
effect of Incubation time
longer time enhances lattice formation
effect of ionic strength of medium
reducing ionic strength by using LISS will enhance some antigen-antibody reactions
second stage of agglutination
formation of aggregated RBCs or lattice formation that are visible
important factors :
immunoglobulin class
# of antigen sites on RBCs
location & proximity of antigen sites on RBC
zeta potential
Zeta Potential
force of repulsion between RBCs in a normal saline suspension
RBC have - charge & + cations form an ion cloud around RBC preventing 2 RBCs from getting close enough to agglutinate
LOWER zeta potential = better
Enhancing Agglutination in vitro
physical methods & enhancement media/ potentiators
physical methods of enhancing agglutination
centrifugation
temperature
pH
AHG
Potentiators for enhancing agglutination
PEG
LISS
Albumin
Enzymes
Anti-Human Globulin(AHG)
anti-human antibodies bind to sensitizing globulin antibodies and form bridges between antibody coated red cells resulting in visible agglutination
strength of reaction is proportional to the amount of globulin coating the RBC
DAT: direct antiglobulin testing
looks for antibody bound ‘in vivo’
for hemolytic immune diseases
looks for anti-IgG & anti C3b/d
IAT: indirect anti-globulin testing
looks for antibody bound ‘in vitro’ - detect IgG bound to RBC in vitro
read for agglutination
Antibody Detection
uses screening cells to detect antibodies w/ specificity to RBC antigens
Antibody ID
IDs specific RBC antibodies
Crossmatch
determines serologic compatibility between donor and patient
Antigen typing
IDs specific RBC antigen in patient or donor
sources of false positive results
contaminated specimen or inappropriate specimen
over-reading
spontaneous agglutination
sample storage
can be caught through the use of an autocontrol
sources of false negative results
failure to adequately wash cells delay in reading under reading excessive shaking of tube inoptimal temperature can be caught through the use of check cells (IgG sensitized RBCs)
IgG Sensitized cells : Check Cell
ensures all negative AHG tests that in fact AHG was added, cells were washed sufficiently, & AHG would be able to react
CHECK CELLS SHOULD GIVE A POSITIVE reaction
