Antihuman Globulin Flashcards
Antihuman Globulin Testing (AHG)
Antibody directed against the Fc portion of human antibodies and/or complement components
Designed to detect the presence of antibody/C’ bound to RBC membranes
Polyclonal AHG
Injection of huma source antibodies/C’ into another species
Rabbit immune response produces many clones that produce antibody
Broad antibody specificity
Monoclonal AHG
Take a plasma cell that produces a specific antibody and fuse it with a myeloma cell to form a hybridoma
Clones grow in tissue culture media and make antibodies
Very specific antibody
AHG Application
AHG enables detection in both in vitro (IAT) and in vivo (DAT) RBC membrane antibody attachment
Primary method of detecting all antibodies except those of the ABO system
Indirect Antiglobulin Test: Antibody Screen
1 drop of reagent RBCs with a known phenotype (screening cells) are added to two drops of patient serum/plasma and incubated at 37C
If an unexpt IgG antibody is present in sufficient numbers, it will bind to the corresponding RBC antigen during incubation
Check Cells
Addition of IgG coated red cells to all negative AHG tests
If Check Cells Agglutinate…
Test was adequately washed prior to addition of AHG reagent
AHG reagent was added to the test tube
AHG was added in an active form
IT DOES NOT MEAN THE TEST WAS RUN CORRECTLY
Direct Antiglobulin Test (DAT)
For in vivo sensitized RBC
Wash two drops of patient RBCs 3 to 4 times
Get a dry button
Add 2 drops of AHG to dry button, resuspend and centrifuge
Remove and observe for agglutination
DAT Application
Autoimmune hemolytic anemia: auto-antibodies coating patient red cells
TxRx: recipient Abs coating donor red cells
HDFN: mom Abs coating fetal/newborn red cells
IAT Application
Detects unexpected antibodies in donor and recipient plasma
Final step in antibody ID
Detect weak D expression
