The document discusses various aspects of immunity including: 1. There are two types of immune responses - the primary response which is slower and involves IgM, and the secondary response which is faster and involves IgG. 2. Humoral immunity involves antibodies defending against extracellular pathogens and participating in hypersensitivity reactions. 3. The cellular immune response involves antigen processing, T cell activation, cytotoxic T cells attacking infected cells. Helper T cells activate other immune cells. 4. Autoimmunity occurs when the immune system mistakenly attacks self-antigens, leading to diseases like rheumatoid arthritis and diabetes. Immunodeficiency diseases impair the immune system's ability to function properly.

1. IMMUNITY
Dr F.B.Irani

2. Types of immune responses

4.  The Primary Response
 concentration of antibodies rises gradually and attains
a smaller peak
 IgM and IgG are produced, but response is mainly
due to IgM.
 Antibody titer returns back to normal within few
days to weeks.

5.  The Secondary Response
 It occurs speedily and intensely, due to the
immunological memory.
 Antibody titer falls very slowly and never returns to
normal, but remains elevated for a longer duration.
 Response mainly due to IgG.

6. Role of humoral immunity
1. Defence against extracellular bacterial pathogens
and viruses.
2. Participates in immediate hypersensitivity
reactions of typeⅠ,Ⅱand Ⅲ
3.Associated with autoimmune diseases.

7. Stages of humoral immune response
1. Antigen processing and presentation
2. Recognition of antigen by lymphocytes
3. Lymphocyte activation(both T and B)
4. Differentiation of B cell into plasma cell
4. Production of antibodies by plasma cells
5.Inactivation of antigen
6. Formation of memory B cells

9. v
Antigen(bacterium)
Macrophage MHCⅡ
Antigen presenting cell
Antigen processing
TCR
Sensitized T cell
Processed antigen Slgs
mlgs
Sensitized B cell
Receptors
Blast cell
Helper Plasma cell
Memory cell
Humoral immunity

10. Antigen
Macrophages (MHC Ⅱ)
Blast transformation
B lymphocytes T lymphocytes
(CD4 ) helper T cells
T-B co-operation
Plasma cells 1. interleukins 2 (IL2)
Memory B cells 2. B cell growth factor

11. Plasma cells Memory B cells
2000 Mol/sec
IgG IgA IgM IgD Ig E
Direct attack Attack through complement
system
Agglutination CLASSICAL ALTERNATIVE
Precipitation (C1 to C9, B and D) (properdin pathway)
Neutralization Neutralization activate C3 and C5
Cytolysis Agglutination
Cytolysis
Chemotaxis, Opsonization

12. THE COMPLEMENT SYSTEM
These are group of plasma proteins which complement
the effects of antibodies in destroying antigen.
They are designated as C1-C9. C1 into C1q, C1r,
C1s. (Total is 11)
Mechanism of complement activation:-
The classical pathway-
The alternative pathway-
The Mannose-Binding Lectin pathway-

13. ROLE OF CELLULAR IMMUNITY
1.Protection against fungi, viruses, intracellular bacteria
(M. tuberculosis, M. leprae, Brucella)
2. Participates in allograft rejections.
3. Participates in delayed hypersensitivity reaction.
4. Role in autoimmune diseases.
5. Provides immunity against cancer.

14. 1. Antigen processing and presentation
2. Recognition of antigen by lymphocytes
3. T Lymphocyte activation
4.Release of differentiated T cells
5.Attack phase of cellular immunity
Stages of cellular immune response

15. Antigen(Bacterium)
MHCⅡ
MHCⅠ
TCRs on T lymphocyte
CD4+ lymphocyte CD8+ lymphocyte
Delayed T cell Helper T cell
TH1 Activate CD8 T cells
TH2 Induce antibody production
Suppressor T cell
Cytotoxic T cell
Cellular immunity
1

16. Antigen
Macrophages
MHC Ⅰ MHC Ⅱ
T Lymphocyte
CD8 T lymphocytes CD4 T lymphocytes
Memory T cell Helper T cell
Cytotoxic T cell TH1 TH2
Suppressor T cell
T-B cooperation

17. Cytotoxic T cells- have receptor protein to bind with
antigen and destroy them by –
1. Perforin (hole-forming protein)mediated killing- in
presence of extracellular calcium.
. 2. Lysis through release of cytotoxic substances
3. Induction of apoptosis by secreting tumour necrosis
factor B (TNF-B)

18. Helper T cell Two types:- TH1 and TH2 .
- Helper T1 cells - secretes cytokines:
1. Interleukin2( IL-2)- activates the CD8+ cells to
differentiate into cytokines T cells and
suppressor T cells (T-T co- operations) .
2.γ interferon ( IFN-γ)- direct ability to kill antigen
bearing cells.
3. Tumour necrosis factor-B (TNF-B)- induces
apoptosis

19. Helper T2 cells secrete interleukins 4, 5, 6, 10 and
13. activate B lymphocytes to produce antibodies
(T-B co-operation)
Suppressor T cells-
- Regulate the activity of Cytotoxic T cells.
- Prevent the Cytotoxic T cells from destroying the
body's own tissue along with invading organism.
- It also suppress the activities of helper T cells

20. AUTOIMMUNITY
Immune response to self- antigen.
Mechanism-
1. Forbidden clones
2. Hidden antigen or sequestrated antigen
3. Neoantigen or altered antigen
4. Cross- reacting antigen
5. Mutations
6.Unbalanced activity of helper & suppressor T cells

21. Autoimmune diseases
Haemolytic anaemia
Pernicious anaemia
Thrombocytopenic purpura
Insulin-dependent diabetes mellitus
Rheumatoid arthritis
Rheumatic fever
Graves disease
Myasthenia gravis

22. IMMUNODEFICIENCY DIESEASES
occurs when body defence mechanisms are impaired.
The defect may be in – Lymphocytes (B and T)
- Natural killer cell
- Phagocytic cell and
- Complement proteins
AIDS (Acquired immune deficiency syndrome)-
caused by- HIV-1 and HIV-2
There is reduction in the number of helper T cells.

23. SAQ:-
1.Active immunity, 2. Passive immunity
3. Innate immunity, 4.Cellular immunity,
5. Acquired immunity, 6. Immunoglobins,
7. Functions of lymphoctes,
8. Humoral immunity 9.. Autoimmunity,
LAQ:-
1. Describe role of T lymphocytes/ B lymphocytes in immunity
2. Describe different types of immunoglobins.