Humoral immunity is mediated by antibodies produced by plasma cells. It involves three phases: induction, expansion/differentiation, and effector. In the induction phase, antigens react with B and T cells. In the expansion/differentiation phase, lymphocyte clones proliferate and mature. In the effector phase, antibodies exert biological effects such as neutralizing toxins, agglutinating pathogens, and complement-dependent killing. Primary responses are slow with low magnitude and IgM, while secondary responses are rapid with high magnitude and long-lived IgG.

1. Humoral Immunity

2.  Is the aspect of immunity that is mediated
by antibodies produced by Plasma cells

3.  The production of antibody involves three
distinct phases
1 Induction phase: Ag reacts with
specific T and B cells
2 Expansion and Differentiation
phase: Lymphocyte clones
proliferate and mature
to a functional stage
3 Effector phase: Antibodies exert
biological effects

4. 1 B cells recognize antigen via surface
antibody (B cell receptor)
2 Ag is internalized , processed and
expressed on the surface of the B-cell
(and other APCs) in association with
MHC II molecules
3 Antigen is recognized by T-helper cells
(CD4+)
4 T cells are activated and differentiated
into TH2 cells

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

8. 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

9. Primary Response:
•Slow in Onset Secondary Response:
•Low in Magnitude Rapid in Onset
•Short Lived High in Magnitude
•IgM Long Lived
IgG (Or IgA, or IgE

10.  Monoclonal Antibodies
Recognize only one epitope on an
antigen
 Polyclonal Antibodies
Recognize multiple epitopes on any one
antigen

11. Functions of Antibodies
1 Bind to and neutralize toxins —basis of
Passive Immunization
2 Bind to and agglutinate pathogens Prevent
them from entering or damaging the cells
3 Opsonize pathogens
4 Cause complement dependent killing
5 Mediate ADCC
6 Provide passive immunity to fetus

13. Disease Diagnosis
1 Demonstration of Antibodies against a
specific pathogen is diagnostic of that
disease eg viral and bacterial diseases
Basis of serological tests
2 Detection of Autoantibodies in
autoimmune diseases

14. Therapeutic Applications
 Targeted monoclonal antibody therapy is
employed to treat diseases such as
rheumatoid arthritis, multiple sclerosis,
psoriasis, and many forms of cancer
 Treatment of Immune Deficiency diseases
by Passive Immunization (human serum)
 Use of Anti-RhD antibodies to prevent
Hemolytic Disease of Newborn