Immune System (copy)

What are pathogens and how do they affect the body?

Disease-causing organisms

Act by invading the human body and living there parasitically, thereby causing disease

Are archaea a class of pathogens?

Not known to cause any diseases in humans

What are the 7 classes of pathogens, from smallest to largest?

• Prion

• Virus

• Bacterium

• Protist

• Fungus

• Arthropod

• Worm

What are the two primary layers of skin?

Dermis

Epidermis

What is the dermis?

Underneath layer

Contains sweat glands, capillaries, sensory receptors, and dermal cells, which give structure and strength to the skin

What is epidermis?

Constantly being replaced as the underlying dermal cells die and are moved upwards

Forms a physical barrier against most pathogens because it is not truly alive

What are the openings in the skin protected by?

Lined with tissue cells that form a mucous membrane

Cells of mucous membrane produce and secrete a lining of sticky mucus

The mucus traps incoming pathogens and prevents them from reaching cells that they could infect

Where are cilia located? What is the function of cilia?

Some mucous membrane tissue are lined with cilia

Hair-like extensions capable of wave-like movement

Movement carries trapped pathogens up and out of mucous-lined tissues such as the trachea

What are common areas that have a mucous membrane?

• Trachea

• Nasal passages

• Urethra

• Vagina

Why may blood clotting be needed?

• Small blood vessels (like capillaries, arterioles, and venules) in the skin are damaged, so pathogens are then able to enter the body

  • Blood escapes from the closed circulatory system

What are plasma proteins? and what are 2 clotting proteins?

Proteins that circulate the blood plasma

Two clotting proteins: prothrombin and fibrinogen

What are platelets? What is their typical cellular life span?

Form in the bone marrow and circulate in the bloodstream

One large cell breaks down into many fragments, and each of the fragments become a platelet

Do not have a nucleus and have a relatively short cellular life span of about 8-10 days

What is the cascade when a small blood vessel is damaged?

1. Damaged cells of the blood vessels release chemicals that stimulate platelets to adhere to the damaged area, forming a “plug”

2. The damaged tissue and platelets release chemicals called clotting factors that convert prothrombin to thrombin

3. Thrombin is an active enzyme that catalyzes the conversion of soluble fibrinogen into a relatively insoluble fibrin

What is fibrin?

A fibrous protein that forms a mesh-like network that helps to stabilize the platelet plug

Cellular debris is trapped in the fibrin mesh, and a stable clot is formed

What is the innate immune system? What is its basis?

First layer of the immune system responds to broad categories of pathogens and does not change during a person’s lifetime

Basis is the ability to recognize things that belong in the human body versus not-self

What are antigens and what do they activate?

Foreign molecules that trigger an immune response

Involves an activation of a group of leucocytes called phagocytes, which are capable of engulfing invading material by endocytosis

What is the adaptive immune response?

Second layer of human immunity

Develops over time and only after exposure to specific antigens of specific pathogens

First exposure to a specific antigen leads to memory cells

What are memory cells?

Specific long-lived white blood cells that are formed during the first exposure

Upon a second exposure to the same pathogen, these specific memory cells can be activated quickly

May be so effective in fighting a pathogen that a person may not even realize that they were exposed a second time

What are phagocytes?

Leucocytes (white blood cells) that are capable of an action called amoeboid movement

What is amoeboid movement?

Cells purposefully extend sections of their plasma membrane, followed by their cytoplasm and organelles

Phagocytes use this type of motion to squeeze their way through capillaries so that they can leave and enter the bloodstream to move through body tissues

What is endocytosis?

Sends out plasma membrane extensions to engulf foreign body

Foreign body is brought inside the phagocyte, where the hydrolytic enzymes of lysosomes digest the invader

What else do antigens activate? What are they chemically (bacterium, protist, fungus, viruses)?

Any substance that induces the immune system to produce antibodies

Most are glycoproteins embedded in the outer membrane of pathogens

Could be the plasma membrane of a bacterium or the outer cells of a protist or fungus

Viruses do not have a plasma membrane, but they do have a protein coat called a capsid (capsid proteins act as antigens

The adaptive immune response is based on many specifics (3):

• Each type of B-lymphocyte makes a specific type of antibody

• Each antibody is specific for one antigen

• Each antigen is part of a specific group of molecules of a specific pathogen

Note: More than one type of antibody can be produced in response to a single pathogen

Specificity of transplants

Other molecules, besides those in pathogens, can be recognized as antigens by our immune system

When organs are transplanted surgically, the organ or tissue transplanted must be matched very carefully by comparing the proteins of the donor and recipient

What are the two blood types?

ABO blood type

Rh blood type

What are the antigens found on the surface of erythrocytes?

A protein

B protein

Rh protein

What is the rule for blood transfusions?

A person cannot receive any of the three possible erythrocyte antigen proteins that they do not already have.

What happens if someone receives a blood transfusion of an incompatible blood type?

A transfusion reaction will occur, as the body identifies it as an antigen

Antibodies will be produced that bind to the donated cells and agglutination (clumping) can occur

Resulting transfusion may lead to minor effects but has been known to be fatal

What are the two major types of lymphocytes?

B-lymphocytes and T-lymphocytes

What is the location of lymphocytes?

Continuously circulate in the blood stream and are contained within our lymphatic system, especially within the lymph nodes

What are B-lymphocytes?

Each type of B-lymphocyte is a biological factor for synthesizing only one type of antibody

What are antibodies?

Y-shaped glycoproteins

At the end of each of the branches of the Y is a binding site for an antigen

What are examples of mechanisms of antibodies for fighting off infection?

If multiple antibodies bind to a cluster of pathogens, a clump is created because each antibody can potentially bind to 2 different pathogens

Makes it easier for phagocytes to find and engulf the entire clump

Virus mechanism of action

Viruses attach to the plasma membrane of a body cell, injecting its DNA or RNA
Cell becomes a cellular factory to make more viruses

Capsids can bind to antibodies, which marks the infected cell to be engulfed by phagocytes

What are two important types of leucocytes that respond in the adaptive immune response?

Helper T-lymphocytes

B-lymphocytes

What do helper T-lymphocytes do?

Chemically communicate with other leucocytes, including B-lymphocytes, to signal the presence of a specific antigen

Process of T-lymphocytes

Helper T-lymphocytes have receptors for MHC-antigen complexes of antigen-presenting cells

Helper T-lymphocytes display antigens on their own plasma membrane

Helper T-lymphocytes release molecules called cytokines after finding a specific antigen to help activate a specific B-lymphocyte

Some helper T-lymphocytes are long-lived and are called memory cells

Process of B-lymphocytes

Each type of B-lymphocyte produces an antibody specific to one antigen

Each type that produces a specific antibody must be activated before it can make antibodies

Some B-lymphocytes are long-lived and called memory cells

Communication between B-lymphocyte and helper T-lymphocyte

An antigen from the pathogen is displayed on the plasma membrane of the B-lymphocyte, and on a receptor of the helper T-lymphocyte

A protein receptor on the B-lymphocyte must match a receptor on the helper T-lymphocyte

Cytokines from the helper T-lymphocyte are released and taken in by the B-lymphocyte

This activates B-lymphocytes

What is the downside of antigen specificity?

The immune system can only maintain a relatively low number of each type of cell that can respond to any one antigen.

What happens when specific B-lymphocytes are needed in an immune response?

B-lymphocytes first become activated and undergo numerous mitotic cell divisions

Become larger, develop many ribosomes, endoplasmic reticulum, and Golgi bodies, all used for antibody production and secretion

What do the activated B-lymphocytes differentiate into?

A few of these are memory cells (will not produce antibodies

The rest form antibody-secreting plasma cells that produce antibodies

How long is the primary immune response?

• Relatively long: almost always sufficient time for symptoms of disease to develop

How long is the secondary immune response?

• Triggered by any second or subsequent exposure to the same pathogen

• Memory cells that were produced during the primary infection are circulating the bloodstream

• These very long-lived cells, now in relatively large numbers, are capable of responding to the same pathogen very quickly

• It is usually so quick that symptoms of the disease do not present, or are quite minor

  • Secondary immune response not only occurs faster but also produces many more antibodies than the first exposure

How is HIV transmitted?

Fluids that can transmit HIV are blood, semen, rectal fluids, vaginal fluids, and breastmilk

Most common ways that HIV is spread from person to person

• Unprotected sex

• Using a hypodermic needle

• HIV-positive mother infects her child during pregnancy, labour delivery, or breastfeeding

Which cells does HIV infect?

The host cells of HIV are known as helper T-lymphocytes or CD4 T-lymphocytes

CD4 is the name of the glycoproteins that are found on the plasma membrane of helper T-lymphocytes and are used by HIV in its mechanism for entering cells

What is AIDS (Acquired immune deficiency syndrome)?

Kill helper T-lymphocytes, which weakens immune response to pathogens

Host is susceptible to opportunistic infections (infections that occur more often or with more severity in people with weakened immune systems

Difference between prokaryotic and eukaryotic cells

Processes of protein synthesis are different

Bacteria (prokaryotic) have a cell wall, a structure that is not characteristic of eukaryotic animal cells

Antibiotics mechanism of action

• Selectively block some of the biochemical pathways needed by bacteria while having no effect on humans or other animal cells

• Many categories of antibiotics depending on the biochemical pathway being targeted

Examples of 2 biochemical pathways being targeted

• Selectively blocks protein synthesis in bacteria, but has no effect on eukaryotic cells’ ability to manufacture proteins

• Another type inhibits the production of a new cell wall by bacteria, thus blocking their ability to grow and divide

Do antibiotics affect viruses

• Viruses have no metabolism, so antibiotics have no effect on them

• Any chemical that could inhibit viral metabolic activity would also be damaging to our own body cells, since viruses make use of our own body cells’ metabolism to create new viruses

Principles of evolution for bacteria

When DNA replication rate is very high, one or more mutations is likely to occur that is consequential

May give a bacterial cell protection from the biochemical action of a particular antibiotic. Bacterial cells that arise from binary fission will all have resistance to the antibiotic

What is zone of inhibition?

Area around antibiotics where it is preventing bacterial growth

Responsible use of antibiotics includes: (4)

• Only prescribing an antibiotic when necessary

• Taking the full course of an antibiotic, and not stopping when symptoms first subside

• Reducing the spread of bacterial diseases by vaccination, hand-washing, and proper food hygiene

• Reducing or stopping the practice of adding antibiotics to farm animal feed

What are zoonotic diseases?

• Infection diseases that can cross species, specifically animal to human

• The pathogen may be a virus, bacterium, protist, or fungus

What are rabies?

• Caused by a virus

• Most human cases are the result of dog bites, although the dog may have received the virus from a wild animal

• Cause a progressive and fatal inflammation of the human brain and spinal cord

• By the time symptoms begin to show in an infect person, it is too late for treatment

• Best defense: preventative vaccination of dogs

What is tuberculosis?

• Bacterial disease

• Humans exposed to this bacterium through cattle

• Airborne transmissions are also possible

• Main symptom is damaged lung tissue

• Growth of tubercules that occur in the lymph nodes of an infected person

What is Japanese encephalitis?

• Caused by a virus

• Transmitted through the bite of a mosquito

• Mosquito receives the virus from either a pig or wading bird

• Few cases have progressed to more serious symptoms, including coma and eventually death

• There is a vaccine that prevents symptoms

What is COVID-19?

• Disease caused by a coronavirus known as SARS-CoV-2

• Shown to transfer easily from humans to other animals, such dogs, cats, and deer

• Vary from asymptomatic to severe and fatal respiratory damaged

• Variants of the virus are continuing to emerge, resulting in increased transmission rates

How do vaccines work?

• Composed of the chemical components of a pathogen after eliminating the disease-causing abilities of the pathogen

• Pathogen or selected antigens are injected into a person

  • Results in a primary immune response that then leaves behind memory cells that can be quickly triggered into action upon reinfection by the pathogen

New approach due to recent advances in vaccine research and technology (RNA vaccines)

• DNA or RNA molecules that code for the synthesis of specific protein antigens are injected

• Body cells take in the nucleic acid and use their normal cell protein synthesis organelles and enzymes to produce antigens

• These antigens are recognized as foreign and stimulate a primary immune response

• Memory cells are produced to provide immunity

What is herd immunity?

• When a large percentage of people in a given area (a herd) achieve immunity to a disease

• There is far reduced chance of the disease spreading

What is percentage difference?

• Comparing two values that mean the same thing at the same time

• Difference between two values divided by the average of the two values, expressed as a percentage

What is percentage change?

• Comparing two values that are separated by time

• Difference between the new and old values divided by the old value, expressed as a percentage