Humoral ImmunityHumoral Immunity

Is the aspect of immunity that is mediated Is the aspect of immunity that is mediated

by antibodies produced by Plasma cellsby antibodies produced by Plasma cells

The production of antibody involves three The production of antibody involves three distinct phases distinct phases

1 Induction phase:1 Induction phase: Ag reacts with Ag reacts with specific T and B cells specific T and B cells

2 Expansion and Differentiation 2 Expansion and Differentiation phase:phase: Lymphocyte Lymphocyte

clones clones proliferate and proliferate and mature to a mature to a functional stagefunctional stage

3 Effector phase:3 Effector phase: Antibodies exert Antibodies exert biological effects biological effects

1 B cells recognize antigen via surface 1 B cells recognize antigen via surface antibody (B cell receptor)antibody (B cell receptor)

2 Ag is internalized , processed and 2 Ag is internalized , processed and expressed on the surface of the B-expressed on the surface of the B-

cell cell (and other APCs) in association with (and other APCs) in association with MHC II moleculesMHC II molecules

3 Antigen is recognized by T-helper cells 3 Antigen is recognized by T-helper cells (CD4+) (CD4+)

4 T cells are activated and differentiated 4 T cells are activated and differentiated into TH2 cellsinto TH2 cells

5 The stimulated T-cells then release 5 The stimulated T-cells then release lymphokines that act upon "primed" B-cells lymphokines that act upon "primed" B-cells (B-cells that have already encountered (B-cells that have already encountered antigen), inducing B-cell proliferation and antigen), inducing B-cell proliferation and differentiation into Plasma cellsdifferentiation into Plasma cells

6 Plasma cells begin to secrete IgM6 Plasma cells begin to secrete IgM

Types of humoral response

•Primary response:

Begins immediately

Predominantly IgM

Appears 48 to 72 hours later

•Secondary response:

Occurs within 24 to 48 hours

Predominantly IgG.

Persists much longer

Result of repeated contact with antigens

Primary Response: •Slow in Onset •Low in Magnitude •Short Lived •IgM

Secondary Response: Rapid in Onset High in Magnitude Long Lived IgG (Or IgA, or IgE

Monoclonal AntibodiesMonoclonal Antibodies

Recognize only one epitope on an Recognize only one epitope on an antigenantigen

Polyclonal AntibodiesPolyclonal Antibodies

Recognize multiple epitopes on any one Recognize multiple epitopes on any one antigenantigen

Functions of AntibodiesFunctions of Antibodies

11 Bind to and neutralize toxins —basis of Bind to and neutralize toxins —basis of Passive ImmunizationPassive Immunization

22 Bind to and agglutinate pathogens Prevent Bind to and agglutinate pathogens Prevent them from entering or damaging the cellsthem from entering or damaging the cells

33 Opsonize pathogensOpsonize pathogens

44 Cause complement dependent killingCause complement dependent killing

55 Mediate ADCCMediate ADCC

66 Provide passive immunity to fetusProvide passive immunity to fetus

Disease DiagnosisDisease Diagnosis

1 Demonstration of Antibodies against a 1 Demonstration of Antibodies against a specific pathogen is diagnostic of that specific pathogen is diagnostic of that disease eg viral and bacterial diseases disease eg viral and bacterial diseases

Basis of serological testsBasis of serological tests

2 Detection of Autoantibodies in 2 Detection of Autoantibodies in autoimmune diseasesautoimmune diseases

Therapeutic ApplicationsTherapeutic Applications

Targeted monoclonal antibody therapy is Targeted monoclonal antibody therapy is employed to treat diseases such as employed to treat diseases such as rheumatoid arthritis, multiple sclerosis, rheumatoid arthritis, multiple sclerosis, psoriasis, and many forms of cancer psoriasis, and many forms of cancer

Treatment of Immune Deficiency diseases Treatment of Immune Deficiency diseases by Passive Immunization (human serum) by Passive Immunization (human serum)

Use of Anti-RhD antibodies to prevent Use of Anti-RhD antibodies to prevent Hemolytic Disease of NewbornHemolytic Disease of Newborn