Antibody Titration

alloantibodies (unexpected antibodies)

result from specific antigenic stimulation

result of immunization caused by pregnancy or prior blood transfusion

once identified, it can be useful to quantify the amount of antibody present

antibodies within a blood sample

detected with an antibody screen

target antigen

two-fold serial dilutions of plasma containing an antibody are prepared and testing against a red cell suspension that possesses the _______

titer level

the reciprocal of the greatest dilution in which agglutination is observed

initial

when new specimens are submitted, the _____- specimen should be testing in parallel

fourfold change

considered significant in titer

titration preparation issues

contamination from a tube with a higher antibody concentration

change pipette tips

homozygous vs. heterozygous target cell

use similar methods (gel vs. tube)

maternal immunization

fetal cells possessing a paternal antigen that the mother does not possess, enter her circulation and stimulate antibody production during pregnancy

D antigen

most immunogenic antigen in maternal immunization

(but other blood group antigens may also immunize)

titers

monitored during pregnancy to look out for maternal immunization

any increase in titer

suggests the fetus is antigen positive and at risk for HDN (hemolytic disease of the newborn)

immunization to D

correlates with an increase in volume of RBCs entering D- mom’s circulation in maternal immunization

hemolytic disease of the newborn (HDFN)

1. baby’s Rh-positive RBCs enter the Rh-negative mother’s blood stream

2. mother produces antibodies against the baby’s RBCs (usually these antibodies do not affect her first baby, but future Rh-positive babies are at risk)

3. if a second baby is Rh-positive, the mother’s antibodies will try to destroy the baby’s RBCs, putting the baby at risk for this

RhoGAM

prevents the Rh-negative expectant mother from making antibodies during pregnancy that could cause HDFN in future pregnancies

as long a sRh-negative mother receives this appropriately during every pregnancy, her babies are at very low risk of developing HDFN

amniocentesis

miscarriage

abortion

chorionic villus sampling

cordocentesis

blunt trauma to the abdomen

rupture of an ectopic pregnancy

other than birth, maternal immunization occurs through these ways

ABO

“Other”

Rh

three classifications of HDN

other classification of HDN

unexpected immune antibodies other than anti-D = Jk, K, Fy, S, etc.

Rh classification of HDN

immune anti-D alone OR immune anti-D with other Rh antibodies - anti-C, anti-c, anti-E, or anti-e

ABO hemolytic disease

mother group O, baby A or B

group O individuals have anti-A and anti-B isoantibodies in their plasma —> fetal RBCs are attacked by 2 antibodies

can occur in any ABO-incompatible pregnancy

occurs in only 3%, is severe in only 1% and <1:1,000 require exchange transfusion

disease is more common and more severe in African-American infants

HDFN other than ABO

if this pregnancy is the immunizing event first baby is not affected or only mildly affected

primary immune response - IgM

during pregnancy, IgM may not be produced in sufficient quantity to cause problems

severity of HDNF in future pregnancies due to “other” immune antibodies is variable

if anti-D affects future pregnancies severely

IgM

primary immune response in HDFN other than ABO

prenatal serologic tests

ABO/D type and antibody screen

if the antibody screen is positive:

• identify antibody

• determine clinical significance

if clinically significant patient history is important, previously affected infant

IgM antibodies are not of concern

titration values or antibody titer

can provide info about the amount of antibody in plasma or the strength of antigen present on the RBCs

titer of antibody

usually determined by testing serial twofold dilutions of the plasma against selected red cell samples

reciprocal

results from serial twofold dilutions of the plasma are expressed as the ______ of the highest plasma dilution that causes macroscopic agglutination

monitoring severity of HDN

includes watching titration values and antibody titer —> amount of antibody and strength of antigen

titer of antibody —> serial twofold dilutions