General features

1. IMMUNOLOGY &
MICROBIOLOGY
By : Dr.D.W.Deshkar

2. The Immune System is the Third Line of
Defense Against Infection

3. Mechanism of Phagocytosis

4. Lymphoid organs

5. Components of the Immune System

6. Antigen Presenting Cell & Mast Cell

7. Protective Immunity To Microorganisms
Specific Defense against microbes is mediated by:
Humoral immunity (antibodies)
Through both
Cell mediated immunity (CMI)

8. Protective Immunity To Microorganisms

9. Humoral Immunity
• B Lymphocytes (Plasma Cells)
– Produced in bone marrow
– Make antibodies (immunoglobulins)
– Antibody Types
• IgG
• IgM
• IgA
• IgD
• IgE

10. Cell-Mediated Immunity
• T Lymphocytes
– Originate in bone marrow
– Altered by passage through thymus
– Responsible for mediation of cellular immunity
– T Lymphocyte Types:
• Helper cells (T4 cells)
• Cytotoxic cells (Killer T cells)
• Suppressor cells
• Memory cells

11. Disorders of Immunity
Autoimmune Diseases
• Hyperthyroidism
• Hashimoto’s
thyroiditis
• Type I diabetes
• Addison’s disease
• Multiple sclerosis
• Myasthenia gravis
• Rheumatic fever
• Crohn’s disease
• Ulcerative colitis
• Rheumatoid arthritis
• Systemic lupus
erythematosis

12. Disorders of Immunity
Immunodeficiency Diseases
Congenital
• B cell deficiency
– Agammaglobulinemia
– Hypogammaglobulinemia
• T cell deficiency
• IgA deficiency
• Severe combined immune
deficiency syndrome (B
and T cell deficiency)
Acquired
• Nutritional deficiency
• Iatrogenic (drugs,
radiation)
• Trauma (prolonged
hypoperfusion)
• Stress
• Infection (AIDS)

13. Antibacterial Immunity
I) Immunity to extracellular bacteria:
1- The innate immunity:
a- Complement activation
b- Phagocytosis
c- The inflammatory response

14. Immunity To Extracellular Bacteria
2- The acquired immune responses:
i-The humoral mechanisms (antibodies)
ii- Cell mediated immune response
i- Antibodies induce immunity through:
a- Neutralization of bacterial toxins
b- Antibodies attach to the surface of bacteria and;
- Act as opsonins, enhance phagocytosis
(Opsonization)
- Prevent adherence of bacteria to their target cells
e.g. IgA on mucosal surfaces
- Activation of complement leading to bacterial lysis
- Agglutinate bacteria, preventing their spread and
facilitating phagocytosis

15. Immunity To Extracellular Bacteria
ii- Cell mediated immune mechanisms:
* Microbes are internalized by Macrophages and
presented to TH cells
* TH cells are activated and release cytokines
which;
- activate phagocytosis their microbicidal
functions
- Stimulate antibody production
- Induce local inflammation

16. Immunity To Intracellular Bacteria
1) Innate immunity
Phagocytic cells & natural killer (NK) cells
- They kill infected cells and secrete IFN-γ
- IFN-γ activate phagocytosis to kill intracellular
microbe
E.g. tuberculosis, leprosy, listeriosis
2) Acquired immunity is by AMI & CMI
Production of antibodies by activated B cells;
- Activation of macrophages to kill intracellular
microbes
- Lysis of infected cells by cytotoxic cells (CTLs)
- Most of these organisms are resistant to
phagocytosis, cause chronic infection and
granuloma formation

17. Anti-Viral Immunity
1) Humoral immunity:
a- Virus neutralization
* In viraemic infections,
Antibodies neutralize virus, preventing its
attachment to receptor sites on susceptible
cells
e.g. Poliovirus, mumps, measles, rubella
* In superficial non-viraemic infections
(infleunza)
Secretory IgA neutralizes virus infectivity at
the mucous surfaces

18. Anti-Viral Immunity
1) Humoral immunity:
b- Antibodies destroy free virus particles
directly by:
i- Aggregation of virus and opsonization
ii- Complement mediated lysis
* Both mechanisms also act on virus infected cells

19. Anti-Viral Immunity
2) Cell mediated immunity:
Cell mediated cytotoxicity, mediated by :
- Cytotoxic T-cells (CTLs)
- NK cells
- Activated macrophages

20. Anti-Viral Immunity
CMI acts on virus infected cells through:
- CTLs kill virus infected cells directly after recognition of
viral antigens on cell surface in association with MHC I
- TH-cells stimulated by viral antigens release cytokines
Cytokines attract and activate macrophages to kill
virus infected cells
- Nk-cells destroy virus infected cells early in infection
before appearance of antibodies
- Antibody-dependent cell mediated cytotoxicity (ADCC):
Antibody binds to virus infected cells such cells are lysed
by NK cells, macrophages and polymorphs

21. Anti-Viral Immunity
3) Anti-viral activity of interferons (IFNs)
1- Virus infected cells produce INF-α;
- INF-α inhibit intracellular replication of viruses
- IFN-α activate NK-cells to kill virus infected cells
- IFNs have no direct effect on extracellular virus
- IFNs act early in viral diseases before antibody
- INFs activity is not specific

22. Anti-Fungal Immunity
Immune response to fungi consist mainly of :
1) Innate immunity is mediated by:
- Neutrophils and macrophages
- Fungi are readily eliminated by phagocytes
2) Acquired immunity (cell mediated immunity)
- CMI acts in a manner similar to its action
against
intracellular bacteria
* Disseminated fungal infection are seen in:
immunodifcient persons

23. Immune Evasion Examples
• Mycobacteria : Inhibits phagolysosome
fusion so that it survives within the phagosome
• Herpes simplex virus : Interferes with TAP
transporter (inhibits antigen presentation)
• Cytomegalovirus : Inhibits proteasome activity
and removal of MHC I from ER
• Epstein-Barr virus : Inhibits proteasome activity;
produces IL-10 to inhibit macrophage activation
• Pox virus : Produces soluble cytokine
receptors to inhibit activation of effector cells

24. Serology
Principles and Interpretation
in Infectious diseases
• SEROLOGY – Antigen – Antibody
Reactions in- vitro

25. Beginning of Serology
• Serology as a science began in 1901.
Austrian American immunologist Karl
Landsteiner (1868-1943) identified groups of
red blood cells as A, B, and O. From that
discovery came the recognition that cells of
all types, including blood cells, cells of the
body, and microorganisms carry proteins and
other molecules on their surface that are
recognized by cells of the immune system.

26. Serology
 A science that attempts to detect signs of infection in a
patient’s serum such as Ab for a specific microbe
 Serological tests based on Abs specifically binding to Ag.
- Ag of known identity will react with Ab in an unknown serum
sample.
- Known Ab can be used to detect Ag in serum
 Ag-Ab reactions are visible by clumps, precipitates, color
changes or release of radioactivity.
 The most effective tests have high specificity and
sensitivity.

27. Types of serological tests
• Precipitation tests
• Agglutination tests
• Complement Fixation test
• Neutralisation test
• Opsonisation
• Immunofluroscence
• Radioimmunoassay (RIA)
• Enzyme Linked Immunoassay (ELISA)
• Chemiluminescence
• Immunoelectronmicroscopic tests
• Immunoblotting.
• DNA Hybridisation
• Polymerase Chain Reaction (PCR)

28. THANKS