Humoral immunity is mediated by antibodies (immunoglobulins) produced by B-lymphocytes. It involves three phases: 1) B-cell activation and differentiation upon antigen recognition, 2) production of antibodies (Ig), and 3) primary and secondary immune responses where the secondary response is quicker and more vigorous than the primary response due to memory B-cells produced during primary response. Humoral immunity provides protection against bacterial and viral pathogens by mechanisms such as neutralization, opsonization, and complement activation.

1. Humoral immunity
Jay Patidar
Roll number :- 40

2. Objectives
• Definition of immunity
• Classification of immunity
• Humoral immunity
• Immunoglobulins
• Activation of humoral immunity
• Humoral immune response

3. IMMUNITY
• Ability of the body to resist invasion by the microorganism and
influence of the toxins that cause tissue damage.
• Newborn and old people have low levels of
immunity.
• It is affected by the nutritional status of an
individual

4. Classification of immunity

6. HUMORAL IMMUNITY
• Humoral response carried out by antibodies
which are produced by plasma cells.
• This immunity is antibody mediated.
• Since antibody produced from plasma cell
present in blood and body fluid {HUMORAL
means body fluid} so termed as humoral
immunity.

7. • Aim of this immunity is to provide defence against
most bacterial and viral pathogen.
• Aim of pathogen ----> To enter the cell and destroy it.
• Principle of antibodies---->Interruption of receptor
linkages between pathogen and cell.
• Result----> Breakdown of interaction between
pathogen and cells due to blocking it by antibody.

8. • Antibodies are produced by B- lymphocytes.
• B- cells produced by bursa equivalents--fetal liver and bone
marrow.
• They acquire receptors to recognize antigen .
• After maturation of B cells they migrate to lymph nodes, bone
marrow, and other tissues

9. • When specifc stimulation occurs------>B lymphocyte specific
for antigen enlarge to form lymphoblasts.
• Lymphoblasts diffrentiates into----> Plasmablast
• Plasmablast produce plasma cells and they produce ---->
Immunoglobulins / Antibodies

10. IMMUNOGLOBULINS
They contain 4 polypeptide chains.
• 2 long chains---> Heavy chain
• 2 short chain--->Light chain
They are of 5 types
• *IgG
• *IgA
• *IgM
• *IgE
• *IgD

11.  IgG:-
• It has gamma heavy chains.
• Most abundant immunoglobulin.
• Passes through placenta.
 IgA:-
• It has alpha heavy chain.
• Present in body secretions.
 IgM:-
• It has mu heavy chains.
• Responsible for complement activation.
 IgD:-
• It has delta heavy chain.
• Involve in antigen recognition by B cells.
 IgE:-
• It has epsilon heavy chain.
• Increase in allergy and parasitic infestations.

12. ACTIVATION OF HUMORAL
IMMUNITY
• Involves stages like :-
• Presentation of antigen
• Activation of B cells
• Differentiation of B cells from plasma cells
• Proliferation of plasma cells and production of
• antibodies
• Destruction of invaders by antibodies
• Formation of memory B cells

13.  PRESENTATION OF ANTIGEN:-
 APC not required to induce humoral immunity.
 B cells act as APC [Antigen Presenting Cell
 ACTIVATION OF B CELLS
 Antigen bind to B cell receptor they get activated.
 B cells also get activated when they cone in contact with MHC antigen
complex of APC.
 DIFFERENTIATION OF B CELLS FROM PLASMA CELLS
 Activated B cells enlarge and transform into lymphoblast called blast
transformation
 PRODUCTION OF ANTIBODIES
 Plasma cells proliferate and produce antibodies.

14. • DESTRUCTION OF INVADERS BY ANTIBODIES:-
• Antibodies attack and destroy by these mechanisms:-
• Immobilizing bacteria---->
• Antibodies prevent spread of infection by preventing movement of bacteria.
• Neutralizing antigens----->
• Antibodies detoxify various bacteria by neutralizing antigens which leads to loss
of ability to induce
• immunological reactions.
• Complement system activation----->
• Antigen antibody complex activate the complement system which kills
mucroorganism.
• Phagocytosis----->
• Antibodies opsonizes antigens and facilitate phagocytosis.
• Antigen precipitation----->
• Antigens precipitate antibodies and make them insoluble which is easily
detected and engulfed by them.

15. • FORMATION OF MEMORY B
CELLS:-
• B cells differentiate into memory B
cells.
• They remain inactive and on
subsequent exposure respond quickly
and more vigorously.

16. • There are 2 types of immune response:-
• Primary response
• Secondary response
• PRIMARY RESPONSE:-
• Response induced when an antigen enters
the body for first time .
• Antibodies developed over period of 1-4
weeks.
• It is mainly due to IgM.

17. RESPONSE
SECONDARY
RESPONSE:-
• Response induced
when antigen enters the
body for second or
subsequent time.
• It will be quick and
vigorous as compared
to primary response.
• It is because of the
immunological memory
due to memory of B
cells.
• Antibodies develop very
fast .
• Mainly due to IgG.

18. SUMMARY
• Humoral immunity is mediated by immunoglobulins
• Immunoglobulins are produced by B-lymphocytes
• Memory cells are also produced
• it has three phases
1. B-cell activation and differentiation
2.Antibodies (Ig) production
3.Primary and secondary immuneresponse (secondary
response>primary response)

19. THANKYOU