Humoral Immunity

presented by

Dr. MAHROO MIRAHMADIAN

Professor of Immunology

Tehran University of Medical Sciences

Antibodies

Antibody Structure and

function

Protein electrophoresis

Multiple Myeloma

Antigen Binding Site

Antibodies are Proteins that Recognize Specific Antigens

Hypervariable regions

Antibody is a flexible molecule

Immunoglobulin Domain

Ig Superfamily

A MW of 45,000 Da

A MW of 50,000 Da

A MW of 100,000 Da

A MW of 50,000 Da

A MW of 25,000 Da

A MW of 150,000 Da

Proteolytic Digestion

Proteolytic Digestion

Antibody classes

IgG subclasses

Opsonization

Complement activation

Neutralization

ADCC

Opsonization of bacteria for phagocytosis by macrophages and neutrophils

Neutralization of toxins Activation of the classical pathway of

complement Antibody dependent cell mediated cytotoxicity

(ADCC) by NK cells. Neutralization of microbes Transfer of maternal antibody across the

placenta and gut.

Effector functions of IgG Antibody

IgG1, IgG3 and IgG4 readily cross the placenta (neonatal immunity) IgG3, IgG1 are effective complement activator, and IgG4 is not able to activate complement. IgG1 and IgG3 bind to Fc receptors on phagocytic cells and thus mediate opsonization.

Effector functions of IgG subclasses

sIgA

Neutralization

Mucosal immunity: secretion of IgA into the lumens of the gastrointestinal and respiratory tract. Neonatal immunity: transfer of maternal IgA from breast milk Neutralization of bacteria, viruses and toxins

Effector functions of IgA antibody

IgM

Effector functions of IgM antibody

Elevated level of IgM usually indicated either recent infection or recent exposure to the antigen.

Isohemagglutinins. Antigen receptor of naive B lymphocyte. Activation of classical pathway of complement. IgM is the first antibody produced in a primary

response to an antigen.

Effector functions of IgD antibody

IgD, together with IgM, is expressed by matureB cell

IgE

Allergen cross-linkage of receptor-bound IgE on mast cells induces degranulation

Mast cells basophils and activated eosinophils bind IgE antibody via

Fc RMast cells contain cytoplasmic granules

that contain mixture of chemical mediators: histamine which make local blood vessels permeable.

Lipid mediators such as prostaglandin D2 and leukotriene C4 and to secret cytokines such as TNF-

ADCC

IgE antibody mediate immediate hypersensitivity reaction.

Antibody dependent cell mediated cytotoxicity (ADCC) involving eosinophils

Effector functions of IgE antibody

Isotype Allotype Idiotype

Idiotype