1. Immunology: Innate Immunity
Lecture 13
Immunology:
Innate Immunity

2. Elie Metchnikoff
Theorized that there are specialized cells within the body that could destroy invading organisms
Studying immature starfish larvae  introduced splinter in larvae, area surrounded by motile cells
Reasoned certain cells within body were responsible for ingesting and destroying foreign matter - phagocytes

3. Immune System Used by our bodies to fend off invaders (microorganisms)
Two different immune response systems:
Innate Immunity
2. Adaptive Immunity
- is able to learn and remember

4. Figure Overview (1 of 3)

5. Cells of the Immune System
Can move from one part of the body to another, traveling through circulatory systems
Always found in normal blood
Some play dual functions in both innate and acquired immune response

6. Where do cells of the Immune System come from?
All originate from same type of cell, hematopoietic stem cell, found in bone marrow
Induced to develop into different types of cells
Some types are already mature when they leave the bone marrow, others differentiate after leaving blood

7. Cells of the Immune System
All immune system cells are called white blood cells, or leukocytes
Can be divided into two main groups:
Granulocytes
Agranulocytes

8. Granulocytes 1. Neutrophils- professional phagocytes
All contain granules filled with chemicals that are important in their function
Three types:
1. Neutrophils- professional phagocytes
- Granules contain antimicrobial substances and degradative enzymes
2. Eosinophils- granules contain substances toxic to multicellular parasites
3. Basophils and Mast cells- blood cells involved in allergic reactions and inflammation

9. Agranulocytes 1. Monocytes Macrophages: professional phagocytes
- present in virtually all tissues
2. Lymphocytes
3. Dendritic cells

10. Lymphocytes
Natural killer (NK) cells- destroy virus-infected and abnormal cells
B lymphocytes and T lymphocytes are involved inadaptive immunity
B cells: produce antibody
T cytotoxic cells: destroy infected host cells
T helper cells: coordinate immune response

11. Dendritic Cells Found in the skin and other points of pathogen origin
They are involved in the activation of acquired immunity

12. Cell Communication
Cells of the immune system must be able to communicate with each other
They use cytokines
Cytokines bind to surface receptors
Then induce change in these cells, such as growth, differentiation, movement or cell death

13. Cytokines 4 kinds: Chemokines: important in chemotaxis of immune cells
Interferons: glycoproteins important in the control of viral infections; also help regulate cells involved in immune response
Interleukins: important in innate immunity, inflammation, and adaptive immunity
Tumor necrosis factors: help kill tumor cells, initiate programmed cell death (apoptosis)

14. The Innate Immune Response
Includes:
Physical, chemical, and microbiological barriers
Phagocytosis
Inflammation
Fever
Complement system

15. Figure 15.3

16. Physical Barriers Skin: microbes sloughed off along with skin cells
Microbes must penetrate several layers
Mucous Membranes: produce mucus to trap microbes
Most lined with cilia

17. Figure 15.2

18. Chemical Barriers Low pH in vaginal and urinary tracts, and stomache
Defensins: short antimicrobial peptides, insert into bacterial membranes and form pores
Lysozyme: degrades peptidoglycan
Interferon: are cytokines that trigger:
macrophage activation
production of substances to interfere with RNA viral reproduction

19. Microbiological Barriers
Normal Flora: not part of immune system, but are part of first line of defense
Protection they provide is considerable
Competitive exclusion of invading microbes
Produce compounds that are toxic to other bacteria
Stimulates immune system, providing a moderate amount of “exercise” to system, thereby enhancing it’s function

20. Phagocytosis Performed by Neutrophils and Macrophages
Phagocytosis is the capture and digestion of foreign particles
Chemokines are cytokines that attract macrophages and neutrophils to infected tissues
Opsonins attach to microbes to increase the ability of phagocytes to adhere (opsonization)

21. Figure 16.6

22. Figure Overview

23. Inflammation This is a coordinated response to tissue damage
Five signs of inflammation: redness, swelling, heat, pain, and loss of function (sometime present)
Vital role of inflammation: destroy injurious agent if possible, contain site of damage, and restore tissue function

24. Figure 16.8a

25. Figure 16.8b, steps 1–3

26. Figure 16.8c, steps 4–6

27. Figure 16.8d

28. Fever
Higher body temperature occurs as a result of certain cytokines called pyrogens
Cytokines carried in bloodstream to hypothalamus
Hypothalamus responds by raising temperature

29. Fever How does raising temperature get rid of microorganisms?
It inhibits growth of many pathogens by at least two mechanisms:
Elevates temperature above optimum growth temperature
Activates and speeds up a number of other body defenses

30. Complement System
Series of proteins that constantly circulate in blood and fluids that bathe tissues
When they detect presence of foreign material, cascade of reactions follows
Complement proteins activated
When activated, cooperate with other host defense systems to rapidly get rid of invader

31. Figure Overview (1 of 5)