Anti-Human Globulin (AHG) Test Lecture Notes

Flashcards covering the principles, history, types, and procedures of the Anti-Human Globulin (AHG) test based on the lecture transcript.

Cold agglutinins

$IgM$ antibodies that react at ambient or room temperature ($22\text{-}26^\circ\text{C}$).

Warm agglutinins

$IgG$ antibodies that react at $37^\circ\text{C}$ and are often called immune antibodies because they are preformed.

Polyclonal Abs

Antibodies that come from different types of B cells, bind to more than one epitope, and are derived from many sources.

Monoclonal Abs

Clones of a single antibody that come from one source and react to one specific antigen, exhibiting monospecificity.

Alloantibodies

Antibodies produced after exposure to non-self components.

Autoantibodies

Antibodies produced in response to self-antigens.

Incomplete antibodies

Non-agglutinating $IgG$ antibodies (classes $IgG1, IgG2, IgG3, \text{ and } IgG4$) that are unable to fulfill their function of agglutination without enhancement.

HDFN

Hemolytic Disease of the Fetus and Newborn; occurs when maternal antibodies sensitize fetal red cells, leading the mother's immune system to destroy the baby's cells.

Anti-gamma globulin

An antibody that reacts with $IgG$ (gamma globulin), such as Rh antibodies.

Anti-beta globulin

An antibody that detects $IgM$ which is bound to the beta globulin complement.

Polyspecific AHG

An AHG reagent containing both anti-human $IgG$ and anti-$C3d/b$, allowing it to detect many epitopes.

Monospecific AHG

An AHG reagent containing only a single antibody specificity, either anti-human $IgG$, anti-$C3d$, or anti-$C3b$.

Gamma heavy chain specific anti-IgG

Antibodies specific for the Fc portion of $IgG$ that react with agglutinating subclasses $IgG2$ and $IgG4$.

Anti-light chain specific anti-IgG

Antibodies that react to the Fab portion of non-agglutinating subclasses $IgG1$ and $IgG3$.

Hybridoma

The product of the fusion between a myeloma cell (abnormal plasma cell) and a lymphocyte, used in monoclonal AHG production.

Ascites

Fluid found in the abdomen of a mouse from which monoclonal antibodies are extracted.

Patent Blue and Tartrazine

The two components mixed to create the green dye used for visual distinction of AHG reagents.

Sensitized cell

A red cell with human globulin (antibody or complement) already bound to its surface.

Direct Antiglobulin Test (DAT)

A test used to detect in vivo sensitization of red cells with bound $IgG$ or complement.

Indirect Antiglobulin Test (IAT)

A test used to detect in vitro sensitization of red cells with bound non-agglutinating antibodies present in serum.

LISS

Low Ionic Strength Saline; an enhancement medium that decreases incubation time and facilitates antibody attachment by lowering the zeta potential.

PEG

Polyethylene Glycol; an enhancement medium that removes water around RBCs to facilitate antibody-to-antigen attachment.

Check Cells

$IgG$ sensitized red cells used as a control in AHG testing to ensure the reagent was not neutralized.

Gel Test

A methodology using a chamber with polyacrylamide gel that acts as a trap for red cells, where a positive reaction shows agglutination within the gel.