11.1 Antibody Production and Vaccination

Self vs non-self

Self = body cells (things that belong in the body)

Non-self = foreign materials

How are cells in the body recognized as ‘self’

All nucleated cells possess unique and distinctive surface molecules that identify it as self.

Name for self markers

Major histocompatibility complex molecules (MHC class I)

How are antigens recognized and triggered to produce antibodies?

Lymphocytes bind to antigen and detect the characteristic shape of an exposed portion called the *epitope*

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The lymphocyte will trigger antibody production which specifically bind to epitopes via complementary paratopes.

Why can red blood cells be transferred without causing an immune response?

Because they are not nucleated

Antigens on red blood cells

Glycoproteins: A, B or AB

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No surface glycoprotein: O

What is a disease

Any conditions that disturbs the normal functioning of the body

What is an illness

A deterioration in the normal state of health of an organism (disease may cause an illness)

Name for diseases that can cross from animals to humans

Zoonoses (rabies, influenza)

Methods of disease transmission

* Direct contact → physical association or exchange of body fluids.
* Contamination → Ingestion of pathogens growing on, or in, edible food sources.
* Airborne → pathogens that travel through the air
* Vectors → intermediary organisms that transfer pathogens without developing disease symptoms

Non-specific immune reaction

Macrophages (type of phagocyte) will engulf pathogens non-selectively and break them down internally

Specific immune response

* A proportion of macrophages will present the antigenic fragments of the pathogen
* The antigenic fragments are presented to specific helper T lymphocytes that, when activated, releases cytokines
* The cytokines stimulate a specific B cell that produces antibodies to the antigen to divide and form clones of B cells (clonal selection)
* Most clones will develop into short-lived plasma cells that produce large quantities of specific antibody
* A small proportion of clones will differentiate into long-live memory cells that provide long-term immunity.

How do antibodies aid in the destruction of pathogens?

* Precipitation - soluble pathogens
* Agglutination - cellular pathogens become clumped for easier removal
* Neutralization - antibodies may occlude pathogenic regions
* Inflammation - antibodies may trigger an inflammatory response within the body
* Complement activation - complement proteins perforate membranes

Delay period

* There is a delay between the initial exposure to a pathogen and the production of large quantities of antibodies
* During this time symptoms may develop

Memory cells

Used to prevent the delay between exposure and production of antibodies.

How do memory cells work

* When B lymphocyte is activated and divides to form plasma cells, a small proportion will differentiate into memory cells
* Memory cells are long living and will survive in the body for many years, producing low levels of circulating antibodies.
* When a second infection occurs, memory cells will react more vigorously to produce antibodies faster.
* As antibodies are produced faster, the pathogen cannot reproduce in sufficient amounts to cause disease symptoms

Allergen

An environmental substance that triggers an immune response despite not being intrinsically harmful

Symptoms to allergens

* Allergic reaction near airways and throat where allergen is encountered
* Severe allergic reaction is anaphylaxis.

How the allergic reaction occurs

* When a B cell encounters the allergen, it will differentiate into plasma cells and make IgE antibodies.
* These IgE antibodies attach to mast cells (type of phagocyte), effectively ‘priming’ them towards the allergen
* Upon re-exposure to the allergen, the IgE-primed mast cells release large amounts of histamine, which causes inflammation.

What do IgE primed mast cells release and what does it do?

Histamine and it causes an inflammatory response that results in allergic symptoms.

Effects of inflammation from histamine

* Improves leukocytes mobility to infected regions by triggering vasodilation and increasing capillary permeability.
* Vasodilation → improves blood circulation & causes redness as vessel moves closer to skin & heat.
* Increased capillary permeability → swelling and pain

Vaccines

* long term immunity
* stimulates production of memory cells
* Vaccine is weakened version of pathogen
* Vaccine may produce adjuvant which boosts immune response

How do vaccines work?

* body responds to vaccine by initiating a primary immune response, which results in memory cells being made
* when exposed to actual pathogen, the memory cells trigger a more potent secondary immune response
* as a consequence of this more potent immune response, you wont get symptoms

Epidemic vs pandemic

Epidemic = region

Pandemic = large geographical area

First disease to have been eradicated by vaccination?

Small pox

Why was eradication of small pox successful?

* small pox is easily identifiable which helped limit transmission
* transmission only occurred via direct contact and there were no animal vectors or reservoirs to sustain the infectious agent
* Infection period is short and virus was stable and did not mutate into alternate strains
* global cooperation and immunity from vaccine was long term so booster was unnecessary.

Monoclonal antibodies

Antibodies derived from a single B cell clone

How are monoclonal antibodies produced?

* An animal is injected with an antigen and produces antigen-specific plasma cells
* Plasma cells are removed and fused with tumor cells capable of endless divisions
* The resulting hybridoma cell is capable of synthesizing large quantities of monoclonal antibody

What can monoclonal antibodies be used for?

* Treatment of rabies
* Detection of pregnancy

How can monoclonal antibodies be used to test for pregnancy

* By testing for hCG hormone which is produced by women during foetal development
* Process is called ELISA
* Free monoclonal antibodies specific to hCG are conjugated to an enzyme that changes the colour of a dye
* A second set of monoclonal antibodies specific to hCG are immobilised to the dye substrate
* If hCG is present in urine, it will interact with both sets of monoclonal antibody (forming an antibody ‘sandwich’)
* When both sets of antibody are bound to hCG, the enzyme is brought into physicial proximity with the dye, changing its colour
* A third set of monoclonal antibodies will bind any unattached enzyme-linked antibodies, functioning as a control