1. STUDY OF IMMUNITY. NON-SPECIFIC RESISTANCE
Immunity. Types of immunity
Innate immunity. Mechanism of innate immunity

2. IMMUNITY
The resistance offered by the host to the harmful effect of pathogenic microbial infection is called immunity. Immunity against infectious diseases is of different types.

3. IMMUNITY INNATE ACQUIRED ADAPTIVE Non specific Specific Passive Active
Natural
Artificial

4. INNATE IMMUNITY
This is basic immunity, which may be genetically passed on from one generation to other generation
It does not depend on prior contacts with microorganisms
It may be non-specific when it indicates a degree of resistance to all infection
It is specific when it shows resistance to particular pathogens

5. The differences between Non-specific Immunity and Specific Immunity
Response is antigen-independent
Response is antigen-dependent
There is immediate maximal response
There is a lag time between exposure and maximal response
Not antigen-specific
Antigen-specific
Exposure results in no immunologic memory
Exposure results in immunologic memory

6. INNATE IMMUNITY
Species immunity: Individuals of same species show uniform pattern of susceptibility to different bacterial infection.
Racial immunity: Within a species different races show differences in susceptibility to infection.
Individual immunity: Individual in population shows variation in their response to microbial infections. Factors influencing level of innate immunity in an individual are: age; hormonal influence; nutrition.

7. DEFENSE MECHANISMS OF BODY
Epithelial surfaces: the intact skin and mucous membrane covering the body confers on it considerable protection against bacteria. They provide mechanical barrier. They also provide bactericidal secretions.
Tissue defenses: If barrier of body is overcome by the organisms, a number of factors in normal tissue and body fluid, play their role.

8. Tissue factor may be divided into:
Humoral factors - the body fluids and organized tissues of human organism naturally contain a variety of antimicrobial agent that kill or inhibit the growth of microbes. The sources and activities of a variety of host antimicrobial substances are summarized in the next slide
Cellular factors

9. Lactoferrin and transferrin
Humoral factors
Substance
Common Sources
Chemical Composition
Activity
Lysozyme
Serum, saliva, sweat, tears
Protein
Bacterial cell lysis
Complement
Serum
Protein-carbohydrate lipoprotein complex
Cell death or lysis of bacteria; participates in inflammation
Basic proteins and polypeptides (histones,lysins and other cationic proteins, tissue polypeptides) 
Serum or organized tissues
Proteins or basic peptides
Disruption of bacterial plasma membrane
Lactoferrin and transferrin
Body secretions, serum, organized tissue spaces 
Glycoprotein
Inhibit microbial growth by binding iron
Peroxidase
Saliva, tissues, cells (neutrophils)
Act with peroxide to cause lethal oxidations of cells
Fibronectin
Serum and mucosal surfaces
Clearance of bacteria (opsonization)
Interferons
Virus-infected cells, lymphocytes
Resistance to virus infections 
Interleukins
Macrophages, lymphocytes
Cause fever; promote activation of immune system

10. MICROBIAL ANTAGONISM
This refers to the protection of the surfaces afforded by an intact normal flora in a healthy organism
E.coli bacteria (yellow)
in the gut are part
of the normal intestinal
flora of humans

11. Phagocyte attacks bacteria
Phagocytosis: Natural defense against invasion of blood and tissue by bacteria or others foreign particles are mediated by phagocytic cell which ingest and destroy them

12. PHAGOCYTOSIS CELLS MAY BE:
Microphages, e.g. polymorphonuclear leucocytes.
Macrophages: histocytes, fixed reticuloendothelial cells; monocytes.
Phagocytosis, a phagocyte (blue) engulfing a yeast
cell (yellow)

13. The process of phagocytosis consist of:
The first phase involves the approach of the phagocyte to the microbe by means of positive hemotaxis
In the second phase absorption of the microorganism on the surface of the phagocyte take place
The third phase is characterized by submergence of the microbe into the phagocyte
In the fourth phase intracellular digestion of the engulfed microbes by the phagocytosis take place

14. Phagocytosis by a Macrophage

16. The neutrophils can form Neutrophil Extracellular Traps (NETs)
The neutrophils can form Neutrophil Extracellular Traps (NETs). Once triggered, the cells undergo a novel program leading to their death. While they perish, the cells release the content of their nuclei. The nucleic acid, mingled with bactericidal enzymes, forms a lethal network outside the cell. Invading bacteria and pathogenic fungi get caught and killed in the NETs

17. Neutrophil granulocytes have trapped Shigella bacteria in NETs (Neutrophil Extracellular Traps)

18. Cilia: The ciliary escalator propels trapped particles out of the respiratory tract
Cilia in the trachea rhythmically beating

19. NON-SPECIFIC IMMUNITY
Inflammation: Tissue injury or irritation initiated by entry of bacteria or of other irritant leads to inflammation
Fever: It is natural
defense mechanism.
It may actually destroy
the infecting organism.
Fever stimulates the
production of interferon
and helps in recovery
from virus infections

20. COMPLEMENT SYSTEM
Complement can be considered as part of the constitutive host defense mechanisms because of its role in inflammation and phagocytosis.
Complement is well known for its ability to react with wide variety of antigen antibody combination to produce important physiological results.
At present complement is known to have 9 distinct components (C1-C9), making a total of 20 proteins.

21. Important physiological effects of complement system
The destruction of erythrocytes as well as other tissue cells.
The initiation of inflammatory changes.
The lysis of bacteria cells.
Enhancement of phagocytosis involving some opsonized particles.

24. Two ways of Complement’s activation
Cell membrane
Classical pathway
Alternative pathway
Damage of membrane
Kinin activation С1 С4 С2 С3
С5-С9
Phagocytosis
Virus neutrali-zation
Immune adherence
Increasing of per-meability of vessels
Virus neutrali-zation
Producing of MAC

25. Complement Fixation Y Methodology Ag No Ag
Ag mixed with test serum to be assayed for Ab
Standard amount of complement is added
Erythrocytes coated with Abs is added
Amount of erythrocyte lysis is determined Ag
No Ag Ag Y
Patient’s
serum Ag Y