Immunology

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What is immunology

Immunology is the study of immune system

3 Lines defense in the human body

1. Skin, mucous membrane, antimicrobial substance

2. Inflammation, fever, phagocytes

3. Humoral and cellular immunity

Innate Immunity

• Present at Birth

• Doesn’t change with use ( doesn’t improve)

• Always available for rapid response to invade microbes

• Does not recognize specific microbes

Adaptive Immunity

• Developed over a lifetime

• Develops more and improve with use ( memory response)

• Extremely specific

1st line of Defense : Skin and Mucous membrane

Skin and mucous membrane are the first line of defense against pathogens that try to enter your body

• Physical and chemical

• Skin provides basic physical barriers

• Epidermis (Physical) - not alive

• Dermis ( Most alive ) ( Chemical - Sebum & Fatty Acid)

Epidermis

• Outer, thinner portion of skin

• Many layers of tightly packed cells

• Topmost layer is dead and contains keratin (protective protein)

• No Blood vessels

• Dry

• Periodic shedding

Skin - Chemical Protection

Skin Contains:

Sebaceous Gland - produces an oily substance called Sebum

Protective film over skin

Lowers pH ( 3-5)

Contains unsaturated fatty acid

• Inhibits bacteria and fungi

Sweat Gland - Chemical Protection

Sweat Gland:

• Perspiration to flush microbes from surface

• Contains lysozyme - enzyme breaks down bacteria cell walls

Mucous membrane - Provide protections

Mucous membrane line the entire gastrointestinal (GI), respiratory and genitourinary tracts

Goblet cells ( type of epithelial cell) secretes mucus, slightly viscous fluid composed of glycoproteins

Around orifices there’s a Mucous membrane secretes mucous viscous substance that helps trap things like microbes & dust ***

Function of Mucous Membrane

Mucus and mucous membrane provide several functions:

• Mucus traps microbes

• Mucous membrane of the nose has hairs that filter inhaled air

• External canal has earwax and hairs that prevents entry

• Cells of mucous membrane of lower respiratory tract are covered in cilia

Ways to EXPEL microbes

Release by: ** gotta know

• Tears ( Lacrimation)

• Saliva Production

• Peristalsis ( Propels food along GI)

• Defecation

• Vomiting Diarrhea

• Urine Flow

Microbiota Defense

Normal microbiota are not usually considered part of the first line of defense, but some of these microbes offer protection by preventing pathogens from colonizing the host by:

• Competing with pathogens for nutrients.

• Producing substances harmful to pathogens.

• Altering external conditions (pH or oxygen availability).

Oral Health

S. Mutans ( BAD) - a prominent cause of tooth decay ( produces lactic acid that dissolves teeth enamel and inhibits growth of other bacteria)

S. Sanguines ( GOOD ) - beneficial bacterium that competes with S. Mutans by producing hydrogen peroxide

Phagocytes

EAT for living

• Phagocytosis: the ingestion of microorganism or other substance by cell

• Phagocyte : Phago- to Eat

• Cye : Cell

  Invade Microbes

How do Phagocytes know what to eat?

Phagocytes can recognize self vs. Non Self

• “Check” pat down cells to recognize parts that do belong and foreign cells

• If contact with foreign cells ( virus) they can respond to them. With receptors called : TLR (Toll-Like Receptors) and PAMPS

• PAMPS helps recognize pathogens by innate immunity * ENGULF It

  • many types of TLR & PAMPS

PAMPS

Pathogens-associated molecular patters are molecules found on pathogens recognized by the innate immunity

TLR

Toll-Like Receptors

are protien receptors on the surface of phagocytes that bind to PAMPS

• Immune cells have pattern recognition receptors

4 Main Stages Phagocytosis

1 - Chemotaxis

2 - Adherence

3 - Ingestion

4 - Digestion

Chemotaxis

Chemical signals attract phagocytes to microorganism

• sense it towards the gradient ( attraction)

Adherence

Attachment of phagocyte to the surface of the microorganism

• attachment **

Ingestion

Plasma membrane extends pseudopods that engulfs the microorganism once engulfed, microbe is in phagosome

• eats it **

Digestion

Microorganism is digested and broken down inside a phagolysosome

phagosome Fuse with lysosome

• Release waste - on what’s not digestible ( poops it)

Where are phagocytes in the body

Circulatory System

• Lymphatic System

• Cardiovascular System

  • Runs parallel from cardio system

  • found around the same spots of arteries and veins

  Phagocytes and other immune cells aggregate in lymphoid tissue and lymph nodes

Inflammation - 2nd line of Defense

Inflammation is a local defensive response to any type of cellular/tissue damage

Cause Damage:

• Microbial Infection

• Physical agents ( Heat, Radiation, Sharp Objects)

• Chemical Agents ( Acids & Bases)

Function of Inflammation

• Destroy the microbe and remove it’s by- products ( like toxins)

• Damage control

• Helps recruit cells & proteins to help repair cells & replace damaged tissue

Cellular Response during Inflammation

Damage cells signals chemicals

• that cause vasodilation ( increase blood flow more leaky)

• Increase permeability ( helps phagocytes move from blood vessel to the infection site)

• Recruitment of phagocytes!!!

Chemical Signals

Cause vasodilation & permeability and attract phagocytes to Local site of inflammation

Cytokines ( Chemical Signal)

Important chemical signal to help recruit phagocytes to local site of inflammation

Interferons - Chemical Signal

• Type of cytokine

• Signals release when cell is infected by virus

Infected cells release interferons to alert neighboring cells - let them know they are infected!

• 2 Phases of migrations reach the infected area

Margination Phase

Phagocyte sticks to endothelium (lining) of blood vessel

• Blood vessel → Tissue

• (Rolling sicking*)

Diapedesis | Extravasation Phase

Phagocyte squeezes between endothelial cell to each infected area

• Squeezing through the epithelium

Signs & Symptoms of Inflammation

• Redness

  • Vasodilation

• Swelling

  • Vasodilation

  • Blood vessel fluid leakage

  • Increase in cell number

• Heat

  • Vasodilation

  • Increase in cell activity

• Pain

  • Damage

  • Pressure

  • Increase nerve sensitivity

Complement - Antimicrobial Defense

Protein-Base antimicrobial defense system

Over 30 different proteins involved

• Activation chain - 30 different protein involved

  Like a cascade - one triggers another, amplifying the effect ( dominos effect)

MAC ( Membrane attack complex)

Complement system putting a hole in the membrane

Complement protein bind together to form a “ pore” in microbe cell membrane causing it to Cytolysis death

Outcome: Inflammation & Cytolysis

Cell - cuts