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Home , Immune system

1 OF THE IMMUNE SYSTEM 2 THE IMMUNE SYSTEM

• The immune system is localized in several parts of the body We all get sick sometimes...but then – immune cells we get better. develop in the primary organs - marrow and What happens when we get sick? (yellow) – immune responses Why do we get better? occur in the secondary organs (blue)

ANATOMY OF THE IMMUNE SYSTEM 3 PASSIVE 4 • Thymus – glandular near the – where T cells learn their jobs While your immune system was developing, you were protected by immune defenses called . These • – -producing located inside certain antibodies traveled across the from the maternal blood to the fetal blood. – blood stem cells give rise to all of the different types of blood cells Antibodies (Y) are also found • – serves as a filter for the blood in milk. – removes old and damaged red blood cells – removes infectious agents and uses them to activate cells called The antibodies received • nodes – small organs that filter out dead cells, , through and other “stuff” to present to lymphocytes last only several weeks.

• Lymphatic vessels – collect fluid (lymph) that has “leaked” out from the blood into the tissues and returns it to circulation

1 INDUCTION OF AN IMMUNE RESPONSE Foreign invaders - , , , and parasites- constantly bombard our body. 5 6 YOUR ACTIVE IMMUNE DEFENSES INNATE IMMUNITY When you were born, you brought with you several mechanisms to prevent illness. This type of immunity is also called nonspecific immunity.

! Innate immunity consists of: ! Innate Immunity Adaptive Immunity • Barriers - invariant (generalized) - variable (custom) - early, limited specificity - later, highly specific • Cellular response - the first line of defense - ‘‘remembers’’ – – inflammatory reaction – NK (natural killer) and mast cells

• Soluble factors

7 8 INNATE IMMUNITY INNATE IMMUNITY Barriers Cellular response

• Physical • Chemical • nonspecific - the same response works against many

– – sweat • this type of response is the same no matter how often it – hair – is triggered – mucous – • the types of cells involved are , – , natural killer cells, and mast cells – • a soluble factor, complement, is also involved

2 9 10 Macrophages (MØ)

• WBCs that ingest bacteria, Phagocytic cells include: viruses, dead cells, dust

Macrophages engulf pathogens and dead cell remains • most circulate in the blood, lymph and extracellular fluid

• Produce / (initiate ) Neutrophils release chemicals that kill nearby bacteria • pus = neutrophils, tissue cells and dead • they are attracted to the site of infection by chemicals given pathogens off by dying cells

• after ingesting a foreign invader, they “wear” pieces of it called antigens on their receptors – this tells other types of immune system cells what to look for – Is an presenting cell

11 12 and E. coli Neutrophils

• WBCs – are phagocytic, like macrophages

• Also called polymorphonuclear cells (PMNs)

• neutrophils also release toxic chemicals that destroy everything in the area, including the neutrophils themselves

©Dennis Kunkel Microscopy, Inc., www.DennisKunkel.com

3 13 INNATE IMMUNITY 14 Phagocytosis (MØ & PMN) Cellular response

• Active process initiated by binding to Complement • Pathogen is surrounded and then internalized • complement is not a cell but a group of

• these proteins circulate in the blood

• complement plays a role in inflammatory responses of both the innate and adaptive immune responses

INNATE IMMUNITY 15 16 Cellular response The Complement (C’) System

Complement • is activated by innate immunity • complement is not a cell but a group of proteins • Recognition by Complement receptors (CR) • CR1, CR2, CR3, CR4, C5a, C3a • these proteins circulate in the blood • Comprised of plasma proteins that when activated forms a – help to recruit to site of inflammation and triggered cascade activate them – Zymogens – activated by the cleavage of other proteases – bind to receptors on phagocytes, helping to remove agent of infection • Precursor – form pores in the invader or infected cell’s membrane (like • Function the NKs do) – Facilitates the uptake & destruction of pathogens by phagocytes – activate mast cells to release and other factors – Induces inflammatory responses

• complement plays a role in inflammatory responses of both the innate and adaptive immune responses

4 17 18 of C’ System INNATE IMMUNITY Cellular response Inflammatory response

• chemical and cell response to injury or localized infection • eliminates the source of infection b • promotes wound healing

Step 1. Circulation to the site increases ! tissue warm, C4b C3b red and swollen + + C2b Bb Step 2. WBCs leak into tissues ! phagocytes engulf and destroy bacteria

19 INNATE IMMUNITY 20 INNATE IMMUNITY Cellular response Cellular response Inflammatory response (cont’d) Inflammatory response (cont’d) have both positive and negative effects on The release of histamine and causes infection and bodily functions local vessel dilation resulting in: POSITIVE NEGATIVE • more WBCs to site • indicate a reaction to • extreme heat ! enzyme infection • increased blood flow ! redness and warmth denaturation and • increased permeability • stimulate phagocytosis interruption of normal • slow bacterial growth biochemical reactions • phagocytes move out of vessels into intracellular fluid (ICF) – increases body temperature > 39° C (103°F) is dangerous beyond the tolerance of some bacteria > 41°C (105°F) could be fatal • edema (swelling) due to fluids seeping from and requires medical – decreases blood iron levels attention

5 21 22 Inflammatory Response The Inflammation Process

Fig 1-4 Kuby 5e

23 24 Inflammatory Response Natural killer cells (NK cells) • instead of attacking the invaders, they attack the body’s own cells that have become infected by viruses

• they also attack potential cells, often before they form tumors

• they bind to cells using an “bridge”, then kill it by secreting a chemical () that makes holes in the cell membrane of the target cell.

• With enough holes, the cell will die, because water rushing inside the cell will induce osmotic swelling, and an influx of calcium may trigger .

6 25 26 Mast cells NK cells and cancer • are found in tissues like the skin, near blood vessels. - Experimental tumor models: - Depletion of NK increases metastases • are activated after antigen binds to a specific type of antibody called IgE that is attached to receptors on the - Administration of activated NK cells results in tumor . regression • activated mast cells release substances that contribute to inflammation, such as histamine.

• mast cells are important in allergic responses but are also part of the innate immune response, helping to protect from infection.

27 28 INNATE IMMUNITY – • Your mom’s antibodies were effective for Soluble factors just a short time at birth, but your can be activated • quickly. It is always your first line of defense during an infection, but it can’t – a chemical () produced by -infected always eliminate the germ. cells that contributes to their death by apoptosis • When this happens, your body initiates a focused attack against the specific • Acute phase proteins pathogen that is causing the infection. – proteins in the plasma that increase during This attack may lead to long-term infection and inflammation protection against that pathogen. – can be used diagnostically to give an indication of • This type of immunity is called adaptive acute inflammation immunity, the customized second line of defense.

7 INDUCTION OF AN IMMUNE RESPONSE Foreign invaders - viruses, bacteria, allergens, toxins and parasites- constantly bombard our body. 29 YOUR ACTIVE IMMUNE DEFENSES

! ! Innate Immunity Adaptive Immunity - invariant (generalized) - variable (custom) - early, limited specificity - later, highly specific - the first line of defense - ‘‘remembers’’ infection 1. Barriers - skin, tears 2. Phagocytes - neutrophils, macrophages 3. NK cells and mast cells 4. Complement and other proteins

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