Lecture 13 – Ch. 43: Immune System I.Overview II.Innate Immunity A. components B. cells...

Lecture 13 – Ch. 43: Immune SystemLecture 13 – Ch. 43: Immune SystemI. Overview

II. Innate ImmunityA. componentsB. cells

IIII. Adaptive/acquired immunity

A. Lymphocytesi. B-cellsii. T-cells

B. humoral vs. cell-mediated immunityC. AntibodiesD. MHC molecules

IV. Immune memory

V. Immune System Problems

VI. Preparation for next lecture

Why do we not get sick EVERY time someone near us sneezes?

Thought Question:

Overview

PathogensVirusesBacteriaMacroparasites

For example…

Virus Bacteria Macroparasites

Influenza Strep Malaria

Ebola Black Plague Sleeping Sickness

Chicken Pox Salmonella River Blindness

West Nile Virus E. Coli Elephantiasis

IrritantsPollenDust

pollen

cilia of tracheal cells

dust

Disease Defenses

A Way In?

Mucus membranes

Eyes

Nose

Mouth

Vagina

Urethra

Skin breeches (cuts, punctures, scrapes)

Antigens = foreign molecules specific to the invader

Immunity Overview

Which cells are exclusively part of the adaptive immune system?

1. Dendritic cells

2. Macrophages

3. B cells

4. Natural killer cells

5. White blood cells

External Barriers

Innate Immunity

Skin

Dry dead cells

Constantly sloughed off

Secretions

Contain natural antibiotics

Mucus physically traps microbes

Dendritic cells – detect foreign particles alert innate and adaptive immune systems

Mast cells – cause inflammation and alert of damaged tissues

Internal Barriers

Innate ImmunityLeukocytes

Phagocytes - ingest foreign particles & cellular debrisMacrophages – consume

many cells

Neutrophils – die upon consumption

Natural killer cells

Attack cancerous or infected body cells

Use proteins & enzymes to lyse cells

Inflammation

Initiated by damaged or infected cells

Histamine release by mast cells

Capillary flow and permeability increased

Phagocytes drawn to area

Innate Immunity

Cytokines – recruit more lymphocytes leads to pus, swelling, redness, heat

Inflammatory “Symptoms”

Warm, red, painful

Result of leaky capillaries

Increased fluid secretions

Removal of dead cells and waste

Pain

Swelling, chemical response

Alerts injured organism

NSAIDs

Innate Immunity

Leukocytes and fluid = pus

Antimicrobial peptides in vertebrates:

the complement – family of proteins, inactivate and lyse infected cells

Interferons – cytokine made by host cells, boosts immune response

Innate ImmunityAntimicrobial peptides first discovered in insects (like Drosophila).

One immune similarity between insects and humans is…..

1. Both use B and T cells

2. Both have skin as a barrier

3. Both engage antimicrobial peptides

4. Both have adaptive immunity

Adaptive Immune System

Acquired/ adaptive immunity –consists of lymphocytes B cells and T cells

Responsible for circulating antibodies, remembering pathogens, destroying infected cells

B cells

Made and mature in bone marrow

Lymphocytes that make antibodies – either secreted or embedded in B cell membrane

Humoral immunity

B cells and antibodies attack pathogens before they enter cells

After encounter pathogen, B cells differentiate into memory B cells and plasma cells


Clonal Selection:


B cell Plasma cell


Plasma cells make and secrete TONS of antibodies, as opposed to memory B cells

Which is NOT a function of B cells?

1. Produce memory cells

2. Secrete antibodies

3. Attack infected cells

4. Make clones of plasma cells

Antibody action

Defend against pathogens in blood or fluid

Can inactivate pathogens by binding to epitopes

Can stimulate phagocytosis

Can neutralize toxins or block adhesion

Can trigger complement system where blood proteins destroy invaders


Antibodies

Produced by B cells

Each composed of two heavy chains and two light chainsConstant region is same

Variable region is unique to antibody

Bind antigens at each end of “fork”


Genes are unique in that can recombine into millions of combinations in different B cells. Transmembrane antigen

receptors inserted in B cells

Immunospecificity

Antibodies are “pieced together” from many genes

Random combinations allow for millions of possibilities


Each B cell produces unique antibodies

Over 100 million different antibodies in body chances of an antigen encountering one that fits are high

How does our body mount an immune attack to a new pathogen (not previously encountered)?

1. By using memory B cells

2. By chance encounter with a B-cell receptor

3. By attacking with macrophages

4. Both (b) and (c)

5. Both (a) and (c)

Adaptive Immune SystemT cells

Made in bone marrow, mature in thymus

Lymphocytes that cozy up to infected cells – two types:

Helper T cells – recognize and bind infected cells

Cytotoxic T cells – bind and lyse infected cells

Cell-mediated immunity

T cells find and attack pathogen-infected cells

Cell-mediated immunityCytotoxic T cells: Insert pores in infected cells, enzymes break down cells

Helper T cells stimulate lymphocyte division

Some T cells develop into memory cells – future protection


T cell receptors – recognize pathogen epitopes ‘presented’ on infected cells

Composed of one alpha chain, one beta chainHave a variable and constant region, similar to B-antibodies


Self-tolerance


All cells have MHC molecules – most body cells have class I (lymphocytes have class II)

MHC molecules displayed on cell surface – each binds a specific peptide foreign fragment then “displays” it on surface.

MHC = major histocompatibility complex

Self-tolerance


T-cells (cytotoxic or helper T) bind to MHC presented antigens

Self-reactive lymphocytes with receptors to self epitopes are eliminated before they leave bone marrow and mature

Which cells have MHC molecules displayed?

1. Most body cells

2. Cancerous cells

3. Immune system cells

4. Transplanted cells

5. All white blood cells

Immune system must remember past victories...

• Memory cells “remember” specific antigens

• May survive for years

• Respond faster and larger to repeat invasion


Memory

Memory B and T cells are able to recognize pathogens and fight off infections immediately


Then why do you keep catching a cold every year?

100+ rhinoviruses

Cold viruses can mutate quickly

Vaccinations take advantage of the immune response

Body is exposed to antigens to stimulate memory cells

Antibiotics aid disease fight

Reduce growth and reproduction of living pathogens (not viruses)

Give immune system time to fight infection

Humans have misused antibiotics “superbugs”Overuse of antibacterial

products

Failure to complete full course of antibiotics

Non-medicinal use of antibiotics

Antibiotics

Allergies

Immune overreaction to harmless antigens

Histamine triggers inflammation

Extreme response can trigger anaphylaxis

Immune System Problems

Autoimmune DisordersImmune system attacks healthy body cells

Lupus, Rheumatoid Arthritis, Multiple Sclerosis, Type 1 Diabetes, Celiac disease, Crohn’s disease

Immune Deficiency Syndromes

Severe Combined Immune Deficiency (SCID): Few/no immune cells produced genetic

Acquired Immune Deficiency Syndrome (AIDS): Due to Human Immunodeficiency Virus (HIV)

Destroys helper T cells

Immune System ProblemsImmune rejection

When tissue without “self” MHC molecules (aka HLA) contact immune system, response mounted

Can be countered by immunosuppressive drugs

What can you do to fortify your immune system?

Thought Question:

Things To Do After Lecture 13…Reading and Preparation:

1. Re-read today’s lecture, highlight all vocabulary you do not understand, and look up terms.

2. Ch. 43 Self-Quiz: #1 – 7 (correct answers in back of book)

3. Read chapter 43, focus on material covered in lecture (terms, concepts, and figures!)

4. Skim next lecture.

“HOMEWORK” (NOT COLLECTED – but things to think about for studying):

1. Compare and contrast: T cells and B cells, the humoral response compared to the cell-mediated immune response.

2. Explain the function and parts of the human innate immune system.

3. Describe the problem with each of the following: allergies, autoimmune disorders, immune deficiency syndromes.

4. Why are people concerned about over-use or misuse of antibiotics?

Lecture 13 – Ch. 43: Immune System I.Overview II.Innate Immunity A. components B. cells...

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