Humoral Immunity Flashcards
What is the definition of immunoglobulins
• Definition: Glycoprotein molecules that are produced by plasma cells in response to an immunogen and which function as antibodies
What is general functions of immunoglobulins, Ag binding and effector
• Ag binding
– Can result in protection
– Valency
• Effector functions
– Fixation of complement
– Binding to various cells
what is the basic immunoglobulins structure
• Immunoglobulins - heterogeneous
• Myeloma proteins - homogeneous immunoglobulins
What is antigen
Antigen - “anything that can be bound by an antibody“ or
that can elicit an immune response (immunogen). Eg: simple chemicals, sugars, small peptides to complex protein complexes such as viruses.
what is haptens ?
Small antigens (haptens) are not immunogenic – they need to be coupled to a carrier to elicit an IR.
Antibodies interact specifically small parts of antigen molecules. These are known as antigenic determinants or epitopes.
what is isotypes, allotypes and idiotypes
• ISOTYPES - antigenic determinants characterizing classes & subclasses of heavy chains, types and subtypes of light chains.
• Allotypes - antigenic determinants specified by allelic forms of the Ig genes -slight differences in the amino acid sequences of heavy or light chains
light chain allotypes – Km (Inv) heavy chain - Gm
• Idiotypes - unique antigenic determinants present on individual antibody molecules or on molecules of identical specificity – specific antibody molecules have the exact same hypervariable regions
What is the immunoglobulins structure
• Heavy & Light Chains
• Disulfide bonds – Inter-chain – Intra-chain
• Variable & Constant Regions
– VL & CL
– VH & CH
• Hinge Region
• Domains – VL & CL
– VH & CH1 - CH3 (or CH4)
• Oligosaccharides( carbo on CH2)
what is the immunogobulin fragments
Ag binding
Complement binding ite
Placenta transfer
binding to fe receptor
immunoglobulins fragments, Fab and Fc
• Fab
– Ag binding
– Valence = 1
– Specificty determined by VH and VL
• Fc
– Effector functions
• F(ab’)2
Human Immunoglobulins Classes ,5
• IgG - Gamma heavy chains
• IgM - Mu heavy chains
• IgA - Alpha heavy chains
• IgD - Delta heavy chains
• IgE - Epsilon heavy chains
Human Immunoglobulin Subclasses (Heavy Chain)
• IgG Subclasses
– IgG1 - Gamma 1 heavy chains
– IgG2 - Gamma 2 heavy chains
– IgG3 - Gamma 3 heavy chains
– IgG4 - Gamma 4 heavy chains
• IgA subclasses
– IgA1 - Alpha 1 heavy chains
– IgA2 - Alpha 2 heavy chains
Human Immunoglobulin (Light Chain)
• Kappa
• Lambda
Subtypes
• Lambda 1
• Lambda 2
• Lambda 3
• Lambda 4
Structure of IgG
• Structure - 7S Monomer
• Properties
– Major serum Ig
– Major Ig in extravascular spaces
– Placental transfer – No Ag binding required ( IgG2)
– Fixes complement (IgG4)
– Binds to Fc receptors (IgG2, IgG4)
• Phagocytes – opsonization, K cells - AD
Structure of IgM
• Structure
– Pentamer (19S)
– Extra domain (CH4)
– J chain(tgh tgh)
• Properties
– 3rd highest serum Ig
– First Ig made by fetus and B cells
– Fixes complement
– Agglutinating Ig
– Binds to Fc receptors
– B cell surface Ig
Structure of IgA
• Structure
– Serum - monomer – Secretions (sIgA)
• Dimer (11S)
• J chain
• Secretory
component
• Properties
– 2nd highest serum Ig
– Major secretory Ig (Mucosal or
Local Immunity) Tears, saliva, gastric & pulmonary secretions
– Does not fix complement
– Binds to Fc receptors on some cells
