1. Human defence mechanisms
Kaiu Prikk
Lecture 2
2016

2. Defence mechanisms Acquired and specific Innate and nonspecific
1. Firstline of defence:
1) physical-, 2) chemical- 3) genetic barriers
Thirdline of defence
Naturally acquired
active: infection
passive: maternal antibodies
2. Artificially acquired
active: vaccination
2. Secondline of defence:
Inflammatory response
Phagocytosis
Complement
Interferons

4. Nonspecific defence mechanisms:
First line mechanisms: is the surface protection composed:
Anatomical barriers: skin, mucous membrane
2. Chemical barriers:
Sebaceous secretions
Tears and saliva – lysozyme
Acidic pH: skin, sweat, stomach, semen, vagina
3.Genetic barriers
Different level of sensitivity and resistance to infectious agents
Malaria, tuberculosis, Leprosy, Fungal infections

5. Anatomical barriers
Skin and mocous mebranes are intact: provide a physical barrier for invading microbes
Hears in nose acts as a filter and eyelaches protect eyes.
3. Sweat & sebum: contain antimicrobial and antifungal substances

7. Secondline of defence:
1. Inflammation:
- occuring as a response to any injury
- is a combination of processes that attempt to minimize injury to tissues
- to maintain homeostasis
Chemotaxis: the movement of white blood cells in response to chemical attractans
Phagocytosis: is a form of endocytosis. The process by which a cell engulfs particles (bacteria,other microorganisms, aged red blood cells, foreign matter, etc.)
The principal phagocytes are blood cells -neutrophils and monocytes

8. Irritant enters tissue – tissue injury cell damage  secreation of inflammatory mediators
Blood vessels dilate, increasing local blood flow
Increased permeality of blood vessel walls
Chemotaxis
heat
redness
edema
Blood proteins form fibrous capsule around injury site
pain
Increased number of white blood cells at injury site
Phagocytosis of irritant

10. The complement system:
is an enzyme cascade that helps defend against infection.
complement proteins occur in serum as inactive enzyme precursors (zymogens) and reside on cell surfaces.
the complement system bridges innate and acquired immunity by
a) augmenting antibody (Ab) responses and immunologic memory
b) lysing foreign cells
c) clearing immune complexes and apoptotic cells

11. Interferons:
- play an important role in the first line of defence against viral infections.
- are induced at an early stage in viral infection (before the specific immune system has had time to respond).
are made by cells in response to an appropriate stimulus
are released into the surrounding medium 
Interferon-alpha (leukocyte interferon)
Interferon-beta (fibroblast interferon);
Interferon-gamma (immune interferon)

12. Inflammation Response to invades:
When body is invaded/attacked by bacteria, viruses, body defends itself:
The phagocytotic immune response: neutrohils, monocytes/macrophages
Antibody mediated immune response: B-lymphocytes secrete antibodies
Cellular immune repsonse: T-lymphocyte activation, cytotoxic T-cells