1. BODY DEFENSE SYSTEM

2. animal/human must defend , against intruders;-pathogen…
animal/human must defend , against intruders;-pathogen…??..bax, virus, fungi, pathogen from air, water, food, environment….
Body defense system/immunity?
DEFINITION:
ability of an organism to recognize and defend itself against pathogen
resisting the attack of many dangerous organisms.

3. IMMUNOLOGY 201
Chapter 1:
Body defense system
Chapter 2
Innate Host Defenses

4. Outcome from today`s lesson…
Understand innate and adaptive immunity
Roles of innate immunity
Component of innate immunity

5. Adaptive /acquired immunity
Body defense system
Innate immunity
External
Physical
mechanical
Internal
Cellular
Immune response
Biological
Molecular
Adaptive /acquired immunity

6. DEFINITION: Innate and Adaptive immunity
Host defenses that produce resistance against infection can be adaptive or innate
Innate defenses: those that act against any type of invading agent
Adaptive defenses: respond to particular agents called antigens (e.g. viruses and pathogenic bacteria)
Only when our resistance fails do we become susceptible to infection by pathogens

7. Adaptive Defenses Respond to antigens by producing protein antibodies
Also involve the activation of the lymphocytes
Lymphocytes: specific cells of the body’s immune system
Antibody and cellular responses are more effective against succeeding invasions by same pathogen than against initial invasions

8. Innate Defenses Physical barriers Chemical barriers Mechanical Barrier
Cellular Barrier
Inflammation
Fever
Molecular defenses

9. Comparison between innate immunity and adaptive immunity
Non specific- acts against many organism
Specific- respond to the specific antigen
Present from birth
Acquired- usually by having disease/ vaccination
Heredity
not
Does not become more efficient after more exposure
The immune system efficiency increased and memorized after exposure
Various types of defense mechanism
Involves mostly lymphocytes cell, that produces B cell and T cell

10. Physical Barriers
Skin and mucous membranes protect your body and internal organs from injury and infectious agents
These two physical barriers are made of cells that line body surfaces and secrete chemicals
human beta-defensin-2 on human skin destroys pathogens by poking holes in bacterial membranes
Mucosa covers those tissues and organs of body cavity exposed to exterior

11. Chemical Barriers
High salt content of sweat inhibits bacteria from growing
Sweat and sebum produced by sebaceous glands have low pH that inhibits growth of bacteria
Acidic pH of stomach is a defense against intestinal pathogens
Lysozyme: present in tears, saliva, and mucus, cleaves peptidoglycan linkage in bacterial cell wall

12. Mechanical barrier Function:- prevent/flush invading microbes in different type of mechanical way
Hair and mucus- nasal, respirotary system
Coughing and sneezing
Urinary flow- remove microbes in urinary tract
Tears and saliva – flush bacteria from eyes and mouth
Vomitting and diarrhea- flush bacteria from digestive tract

13. Cellular Defenses – Defensive Cells
Blood consists of about 60% liquid called plasma and 40% formed elements (cells)
Formed elements: erthyrocytes, platelets, and leukocytes
Leukocytes are defensive cells important to adaptive and innate host defenses

14. Formed cellular elements of the blood

15. Granulocytes
Have granular cytoplasm and an irregularly shaped, lobed nucleus
Include:
Basophils: release histamine which helps initiate inflammatory response
Mast cells: prevalent in connective tissue, release histamine, and associated with allergies
Eosinophils: present in large numbers during allergic reactions
Neutrophils (polymorphonuclear leukocytes): phagocytic cells that guard skin/mucous membranes against infection
Dendritic cells: phagocytic cells that resemble nerve cells

16. Agranulocytes Lack granular cytoplasm with round nuclei Include:
Monocytes: phagocytic cells derived from myeloid stem cells
Lymphocytes: derived from lymphoid stem cells and contribute to adaptive host immunity
Lymphocytes circulate in blood and are found in lymph nodes, spleen, thymus and tonsils

17. Phagocytes Cells that literally eat or engulf materials
Monocytes, dendritic cell, neutrophils, eosinophils,
Patrol, or circulate through body, destroying dead cells and cellular debris
Guard the skin/mucous membranes against invasion by microorganisms
Macrophages(formed from monocytes): “big eaters” that destroy not only microorganisms but also larger particles

18. Macrophage moving over a surface

19. The Process of Phagocytosis
Phagocytes digest and destroy invading microbes and foreign particles by a process called phagocytosis
Phagocytic cells must:
Find Adhere to Ingest
Digest the microorganisms

20. Phagocytosis of two bacterial cells by a neutrophil

21. Chemotaxis
Phagocytes in tissues first must recognize invading microorganisms
pattern recognition receptors (PRRs) on the phagocytic cells recognize molecular patterns unique to pathogen
Phagocytes release cytokines that have specific roles in host defenses
Chemokines: a class of cytokines that attract additional phagocytes to site of infection

22. Adherence and Ingestion
The ability of the phagocyte cell membrane to bind to specific molecules on the surface of the microbe is called adherence
Antiphagocytic capsule: the most common means by which bacteria avoid phagocytosis
Complement system: coat microbes with antibodies to aid phagocyte in adherence
Phagosome: pseudopodia fuse and enclose microorganism within this cytoplasmic vacuole

23. Digestion
Phagocytic cells have several mechanisms for digesting and destroying ingested microbes
Phagolysosome: lysosomes with digestive enzymes fuse with phagosome membrane
Macrophages use other metabolic products to kill ingested microbes:
Oxygen to form hydrogen peroxide
Nitric oxide and superoxide ions

24. Extracellular killing
What if the intruder is larger than the Macrophage/neutrophils?
The killing need to be done extracellularlly by…
Eosinophils- excreting toxic enzymes (MBP) –kill worm
Natural killer cell- secrete cytotoxic proteins that kill intracellular

25. Molecular Defenses Involve the action of interferon and complement
Interferon: interfered with viral replication in other cells
Humans have three groups of interferon (alpha, beta, and gamma)
Antiviral enzymes

27. Complement
Refers to a set of more than 20 large regulatory proteins that play a key role in host defense
General functions of the complement system are:
Enhance phagocytosis
Lyse pathogens directly
Generate peptide fragments that regulate inflammation and immune responses
Works as a cascade: a set of reactions that amplify some effect

28. Complement lesions in cell membranes

29. Activation of the classical complement pathway

30. The mechanism by which interferons alpha and beta act

31. Inflammation
The body’s defensive response to tissue damage from microbial infection
Characterized by signs:
an increase in temperature
redness
swelling
pain at infected or injured site

33. Steps in the process of inflammation and subsequent healing

37. Fever
The elevation of body temperature to kill invading agents and/or inactivate their toxic products
HOW?
Raises temperature above opt. temp. of pathogens
Microbial enzymes or toxins is inactivated
Increase immune response
Phagocytosis is enhanced
Antiviral interferon production is increased
Fever makes patient lie to rest..
Increased breakdown of lysosomes causing death of infected cell and microbes

38. A Summary of the body’s nonspecific defenses