MICI 3115 Lecture 5: Antibody Structure and Function

These flashcards cover key concepts from antibody structure and function, classification, and their immunological significance.

Antibody (Immunoglobulin)

Glycoproteins on B cell surfaces and secreted by plasma cells, present in blood serum and secreted fluids, that activate complement pathways, enhance phagocytosis, and neutralize toxins.

B Cell Receptor (BCR)

Membrane-bound immunoglobulin molecules that act as antigen receptors for B cells, consisting of mIg and Ig-α/Ig-β heterodimer.

Monomer

A single molecular unit, as seen in immunoglobulin classes IgA, IgD, IgE, IgG, and IgM which consist of heavy and light chains held by disulfide bonds.

Variable (V) Region

The region of antibody heavy and light chains characterized by a variable amino acid sequence that forms the antigen-binding site.

C Region

Constant regions of heavy and light chains that have a relatively constant amino acid sequence, affecting antibody stability and interactions.

Immunoglobulin Epitopes

Determinants located in the constant and variable regions of antibodies that define heavy chain classes/subclasses and contribute to antibody specificity.

Opsonization

The process where antibodies promote phagocytosis by enhancing the interaction of antigens with phagocytes.

Hypervariable Regions

Regions within the variable domain of antibodies that exhibit greater amino acid sequence variability and form the antigen-binding site.

Hinge Region

A flexible region between antibody heavy chain domains that allows for movement and flexibility in binding to antigens and effector molecules.

Monoclonal Antibodies

Antibodies derived from a single B cell clone, specific to one epitope, created by fusing B cells with myeloma cells.

IgG

The most abundant immunoglobulin in serum, responsible for neutralizing toxins, opsonizing microbes, and activating the classical complement pathway.

IgM

The first immunoglobulin class produced in a primary immune response, expressed as a pentamer, effective in agglutination and complement activation.

IgA

An immunoglobulin present in serum as a monomer and in secretions as a dimer, important for mucosal immunity.

IgE

Immunoglobulin that binds Fc receptors on mast cells, involved in allergic responses and defense against parasites.

IgD

An immunoglobulin present in low levels in serum, mainly found on B cell surfaces, involved in activating basophils.