General Biology II: Adaptive Immunity

Lymphocytes

White blood cells that are both in innate and adaptive

Adaptive Immunity

Although this part of immunity is not ready, we will use innate immunity in the meantime to defend our body systems

Antigen

Any foreign substance that triggers a B or T response → protein or large polypeptide on the surface of cell (found on pathogen, blood or tissue cells)

Epitope

Specific exposed region on surface of antigen (protein on pathogen) which will bind to its specific antigen receptors on immune cells → each B or T cell will have recognizable/specificity for a specific epitope

B-Cells

Will remain in the bone barrow to develop, which will create antibodies to defend against pathogens in blood

T-Cells

Will leave bone marrow to go to thymus to develop → attack infected cells and defend against pathogens that entered the cell

Antibodies

What will B cells create to defend?

In the bone marrow

Where will B cells develop?

Pathogens

What are the B cells defending against?

Y-shape receptors

What type of receptors do B cells have?

V-region

within 2 type of the Y shaped region where each tip is the binding site for a specific antigen

1) Pathogen spotted → B cells antigen receptors bind to antigen (tips of U)

2) B cells will secrete the soluble form of receptors

3) Antibodies secreted (technically your protein or immunoglobin)

SEQ B-cell activation

Antibodies

A Y shaped structure blood cell antigen receptors that do the actual defense against pathogens, not membrane bound but soluble and secreted by B cells

1) Pathogen spotted → B cells antigen receptors bind to antigen (tips of U)

1st step of B-cell activation

2) B cells will secrete the soluble form of receptors

2nd step of B-cell activation

3) Antibodies secreted (technically your protein x immunoglobin)

3rd step of B-cell activation

In your thymus

Where do your T cells develop?

No, they will target infected cells

Do T-cells make antibodies?

V-region

This region will bind to your antigen (just like in B-cells)

T-cell antigen receptors

These receptors will only bind to fragments displayed by other cells

Pathogen detecting cells like the Antigen Presenting cell and infected cells

How are antigen fragments displayed?

Antigen Presenting cell

Cell that will display antigen fragments in the T cells

1) B & T cell diversity

2) Self tolerance (recognition of self)

3) Immunological memory

4) Proliferation

What are the 4 characteristics of adaptive immunity?

B-Cell + T-Cell diversity

When body is ready to respond to an unbelievable number of pathogens of antigen entering body (about 10⁶ different B-Cell receptors and 10 × 10⁶ different T- Cell Receptors)

Self-Tolerance

This will recognize itself (AND WON’T ATTACK ITSELF) → due to surface proteins (unique)

Proliferation

This is for B or T cell once activated and it will have a downward effect → a cause

Effector Cells

These will immediately attack Antigen producing cells

Memory Cells

These are long lived that will give rise to effectors cells and ready to divide if antigen appears again

Immunological memory

Act as long term protection due to prior infection

Secondary Immune Response

Reaction to same antigen (2-7 days) and faster, prolonged due to already experiencing this antigen

Primary Immune Response

Response to first exposure to antigen (10-17 days) and contain effector cells that can either be B or T cells

Humoral Response or Cell mediated response

What are the 2 responses that a helper T cell can carry out?

Helper T-Cells

These will not directly kill pathogens/infected cells, but can only signal to trigger other immune cells

1) Pathogen infects you as Antigen binding proteins displays antigen fragment

2) Helper T cells will be activated by APC displaying antigens (antigen receptors to antigen fragment)

3) Will stimulate APC to produce cytokines by autocrine or paracrine signals

4) Cytokines trigger Cytotoxic t-cells & B-Cells

SEQ the antigen response pathway

Perforin

Will form pores in infected cell’s plasma membrane

Granzymes

Infected cells via endocytosis to initiate apoptosis

Cytotoxic T Cells

In response to the helper T cell, this will use toxic proteins to kill cells already infected by viruses → perforin & Granzymes

1) Will become active when it meets an antigen and respond to extracellular pathogens

2) Will proliferate (multiply B cells)

3) Antibodies are secreted

4) Marked pathogen/target cells for destruction

5) Lead to 3 mechanisms → Neutralization & Opsonization or the complement system

SEQ B-cell activation

Neutralization

Bind to surface of virus so it will not be able to enter host cells

Opsonization

Will bind to surface of bacteria to promote phagocytosis

Complement System

Will bind to Ag Protein complex to create pores in forei that lead to the lysis of cells

1) Will become active when it meets an antigen and respond to extracellular pathogens

1st step of B-cell activation

2) Will proliferate (multiply B cells)

2nd step of B-cell activation

3) Antibodies are secreted

3rd step of B-cell activation

4) Marked pathogen/target cells for destruction

4th step of B-cell activation

5) Lead to 3 mechanisms → Neutralization & Opsonization or the complement system

5th step of B-cell activation

Vaccines

This is a variant/derivative of pathogen, your goal is to build resistance just for stimulating immune response

Line alternated vaccines

Weakened infectious organisms (polio → sabin vaccines, yellow fever, small pox)

Inactivated vaccines

Killed inactivates (Polio → Salk vaccine, pertussis, rabies)

Subunit Vaccines

Small part of pathogen (Influenza Type B)

DNA Vaccines

Injection with genetically engineered DNA that produce an antigen

mRNA vaccine

Protein instructions given to cell → cell makes and displays new protein stimulating adaptive immune response

Antigenic Drift

Small changes in viral antigens due to mutation

Antigenic shift

Major changes in viral antigens due to viral reassortment or recombination

A change in function

What happens when there is a change in protein’s shape?

Strain Replacement

Less common strain will replace a common one due to successful vaccination against common strain

Many of the unvaccinated individuals will not get the disease

What happens if most of the population is vaccinated?

Reproduction

When an average number of people of a single individual can infect due to genetics passing through