detection of foreign antibodies Flashcards
immune alloantibodies
formed as a response to exposure to foreign (non-ABO) RBC antigens
naturally occuring alloantibodies
formed without exposure to RBC antigens
passively acquired antibodies
antibodies produced in one person and transmitted to another via PLASMA containing blood products or IV immunoglobulin( IVIG) or rhogam
autoantibodies
directed against RBC antigen on patient’s own cells; normally universal reactivity (ex. anti-U, anti-I)
clinically sig antibodies
antibodies that decrease survival of RBC’s that possess the target antigen
ONLY about 1% of the population of recipients has a detectable
RBC alloantibody (why we only screen)
85% of D-negative patients develop
anti-D when exposed to D antigen
all other antibodies develop in ______ or less of antigen-negative patients when exposed to that antigen
3%
2 populations that need to be screened for unexpected antibodies
donors of allogenic units and patients scheduled to receive a transfusion
WHEN possible who else should receive a screen
OB patients and transplant patients
testing when there is an antibody present MUST include what phase
AHG
IAT is enhance with
LISS or PEG
enhancement media lowers _____ ________ around the cells allowing IgG to crosslink and form agglutinate
zeta potential
If you use LISS there is an additional step
read after 37 incubation which can reveal IgG and IgM
what is used to screen transfusion patients
2 or 3 cell panel
RBC’s are also type ___ to avoid interference with ABO antibodies
O
gel cards
used to reduce steps and tech error
in gel cards cells move through ______ and if the antibody bound is it gets stuck in gel; unbound (negative) cells move to bottom
IgG
solid phase testing (echo)
RBC antigens fixed to wells, 37 incubation with LISS allow binding of patient antibody to antigen on the well surface
solid phase and gel testing reactivity looks opposite of what testing
tube testing
low titer antibodies can be missed especially if they show
dosage
about 25% of antibodies
drop below detectable limit within 7 months (this is why it’s important to put in patient history)
info you may want if ID difficult
transfusion history/ preg, major diagnosis, current medications, demographic, previous blood bank history
useful testing in hard cases
autocontrol results, DAT results, tube testing
varying reaction strengths can point to
multiple antibodies or dosage or both
positive reactions at multiple phase can suggest
multiple antibodies or unusual antibodies
to confirm a antibody use
3 pos/ 3 neg rule
where to start with difficult antibody ID
run more cells
if there are multiple antibodies present you need to select cells that are
positive for antigen you want and negative for antigen that will call interference
groups showing dosage
duffy, Rh, Kidd, MNS (duffy the kidd monkey loves M and N’s)
if your autocontrol is negative
you probably have multiple alloantibodies
you can use a negative autocontrol as a
rule out cell
enzymes that alter reactivity of RBC antigens
papin, bromelin, ficin, and trypsin
groups enhances by enzymes
Rh, Kidd, Lewis, I, P
groups destroyed by enzymes
duffy, MN, Ss, Xg
DTT can be used with either
plasma or cells
DTT breaks
disulfide bonds
plasma treated with DTT has
IgM inactivated
ZZAP =
DTT + papain
ZZAP destroys
KELL
ZZAP enhances
P1 and P
adsorption
use patient’s red cells with known antigenicity to remove one antibody from the plasma and use remainder to ID underlying antibodies
autoadsorption
wash patient’s cells, elute present antibody, incubate with plasma (lose reactivity with plasma because autoantibody adsorbed) and plasma can be used for other alloantibodies
homologous adsorption
patient has low RBC count, they are antigen typed and then a closely matched cell can be used to absorb antibody from plasma
differential adsorption
absorbs certain antibodies with a known cell and test plasma for any remaining antibodies; choose a cell that has the antigen you want to eliminate and lacks antigen you suspect
differential adsorption will absorb every
positive antibody
cold panel
run antibody screen AND autocontrol by adding 3 drops of patient plasma to cells and incubate for 15 min in fridge (cold antibody will be shown here )
prewarm
the screen and any ID going to be run using plasma and cells that have been warmed to 37 degrees and washed with 37 degrees saline (removed interference from cold antibody)
neutralization uses
NON RBC substances
saliva from a secretor will have lewis and ABH antigens
useful for rare ABO subtypes
breast milk contains
I antigen
hydatid cyst fluid, pigeon droppings, and turtle dove egg white
neutralize anti-P
if you lose reactivity on the enzyme-treated panel
suspect an antibody against an antigen that is destroyed by enzymes
if control is positive
invalid
darathumb immunotherapy
monoclonal IgG1k that binds CD38
CD38 is
overexpressed on myeloma plasma cells
CD38 is destroyed by
ZZAP (will allow other alloantibodies to be seen) (genetic testing is better)
if you use ZZAP make sure the patient receives
Kell- negative units
