CLLS 3311 Advanced Clinical Immunohematology. Antigen and Antibody Reactions. Demonstration of red cell antigen-antibody reactions is key to immunohematology. AABB Technical Manual.
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Antigen and Antibody
AABB Technical Manual
Substance capable of eliciting an immune response when introduced into a immunocompetent individual to whom it is foreign.
Ability of an antigen to react with the products of an immune response
Antigenic determinants - structural site where the antibody combines with the antigen.Antigen/Antibody Reactions
Most common forms of Blood Group Antigens:
Size, shape, rigidity, location, number of determinants (epitopes), dose, route of entry, and genetic factors.
Normally…don’t forget autoimmune processes
Glycolipids: ABH, Le, Ii and P antigens (Ag)
Proteins: Rh, M, N antigensCharacteristics of Antigens
Phase of Reactivity
Complement (C’) Activation
Warm: reacts best at 37oC
Can cross the placental barrier
Poor to good C’ activators. Two IgG required to activate C’ to completion.
Usually clinically significant RBC immune AntibodyCharacteristics of IgG Class Antibodies
Phase of reactivity
Cold: reacts best at 4-10oC
Cannot cross the placental barrier
GOOD (most) complement activators - one IgM can activate C’ to completion
“Usually” NOT clinically significant, Non RBC immune.Characteristics of IgM Class Antibodies
IgM Antibody(Pentamer Structure)
Images provided by textbook: Figure 14.3, page 97, Kuby
Immunology, 4th Edition, W.H. Freeman and Company
Two Stage Process:
This represents what occurs during stage one of agglutination: Sensitization
Antibody molecules attach to their corresponding Antigenic site (epitope) on the red blood cell membrane. There is no visible clumping.
This represents what occurs during stage 2 of agglutination: Lattice Formation
Antibody molecules crosslink RBCs forming a lattice that results in visible clumping or agglutination.
van der Waals bonds
Antigen and antibody complexing is REVERSIBLE.
Concentration of Ag and Ab also affects agglutination reactions, both the first and second stages.
Size of the Immunoglobulin
Number of binding sites
Location and Number of Antigenic Determinants
Waters of Hydration
Mixed Field Agglutination