adaptive immunity part 2, first part

What is an antigen challenge?

The first encounter between an immunocompetent lymphocyte and an invading antigen.

What triggers activation of an immunocompetent B cell

An antigen binds to receptors on the B cell surface.

What happens after an antigen binds to a B cell receptor?

1. Antigen binds B cell receptor.

2. Adjacent receptors become cross-linked.

3. Complexes are internalized by endocytosis.

4. Clonal selection is triggered.

What is clonal selection?

Activated B cells multiply to produce identical copies called clones.

What are the two cell types produced during clonal selection?

• Plasma cells

• Memory B cells

What is the function of plasma cells?

They secrete antibodies.

What is the function of memory B cells?

They provide a rapid response if the same antigen enters the body again.

How many antibodies can one plasma cell secrete each second?

: About 2,000 antibodies per second.

What is the lifespan of a plasma cell?

about 4-5 days

Are memory B cells short-lived or long-lived?

Long-lived.

What is the primary immune response?

The immune response that occurs during the body's first exposure to an antigen.

: How long does the primary immune response usually last?

About 3–6 days.

When are peak antibody levels reached during the primary immune response?

about 13 days

What is the secondary immune response?

The immune response after re-exposure to the same antigen.

Why is the secondary immune response faster?

Because of memory B cells (immunological memory).

How long does it take the secondary immune response to exceed primary antibody levels?

about 2-3 days

How do antibodies produced during the secondary immune response compare to those in the primary response?

They bind antigens with greater affinity.

How long do antibody levels remain elevated during the secondary immune response?

Weeks to months

How long can some memory B cells live?

A lifetime.

Put the steps of B-cell activation in order.

1. Antigen binds B-cell receptor.

2. Receptors are cross-linked.

3. Endocytosis occurs.

4. Clonal selection begins.

5. B cells multiply (clones).

6. Clones become plasma cells or memory B cells.

7. Plasma cells secrete antibodies.

8. Memory B cells remain for future protection.

What are the characteristics of the primary immune response?

• First exposure to an antigen

• Lasts 3–6 days

• Peak antibodies around 10 days

• Slower response

• Lower antibody levels

• Lower antibody affinity

• Generates memory B cells

Clonal selection results in the production of:

• A. Macrophages only

• B. Plasma cells and memory B cells

• C. T cells only

• D. APCs

B

Which cells secrete antibodies?

• A. Memory B cells

• B. Plasma cells

• C. T cells

• D. Dendritic cells

B

What are the characteristics of the secondary immune response?

• Re-exposure to the same antigen

• Responds in 2–3 days

• Faster and longer-lasting

• Higher antibody levels

• Higher antibody affinity

• Uses memory B cells

• Antibody levels stay high for weeks to months

• Some memory B cells last a lifetime

During the primary immune response, peak antibody levels occur around:

• A. 2 days

• B. 5 days

• C. 10 days

• D. 30 days

C

The secondary immune response is:

• A. Slower than the primary response

• B. Faster because of memory B cells

• C. Only produces plasma cells

• D. Weaker than the primary response

B

What is active humoral immunity?

Immunity that occurs when B cells encounter an antigen and produce their own antibodies.

What are the two types of active humoral immunity?

Naturally acquired

• Artificially acquired

What is naturally acquired active immunity?

Immunity gained through natural exposure to bacterial or viral infections.

What is artificially acquired active immunity?

Immunity gained through vaccination.

What do vaccines contain?

Dead pathogens, attenuated (weakened) pathogens, or parts of pathogens.

What does "attenuated" mean?

Living but greatly weakened.

How do vaccines work?

They expose the immune system to antigens without causing the full disease, allowing the body to develop immunity.

Why are vaccines beneficial?

They reduce or eliminate the discomfort of the primary immune response while creating immunity.

What are booster shots?

Additional vaccine doses that strengthen or intensify the immune response.

Which diseases have vaccines greatly reduced or eliminated?

Smallpox, whooping cough, polio, measles, hepatitis B, tetanus, and pneumonia.

Which helper T cells do most vaccines primarily target?

TH12 cells

Why don't most vaccines produce strong cellular immunological memory?

Because they mainly stimulate TH2 cells rather than TH1 cells.

What are two possible disadvantages of vaccines?

• May rarely cause disease if the pathogen is not weakened enough.

• May trigger allergic reactions.

What are two newer vaccine types that may reduce allergic responses?

• Naked DNA antiviral vaccines

• Edible vaccines

What is passive humoral immunity

Immunity gained by receiving antibodies made by another person or animal.

Where do passive antibodies come from?

The serum of an immune human or animal donor.

Does passive immunity produce immunological memory?

NO

Why is passive immunity temporary?

: The borrowed antibodies naturally break down over time.

What is naturally acquired passive immunity?

Antibodies passed from a mother to her fetus.

How long can maternal antibodies protect a baby?

for several months after birth

What is artificially acquired passive immunity?

Receiving pre-made antibodies through medical treatment.

Give three examples of artificially acquired passive immunity.

• Gamma globulin

• Antivenoms

• Antitoxins

Active Humoral Immunity Characterstics

• Your own B cells make antibodies.

• Triggered by infection or vaccination.

• Produces memory B cells.

• Protection is long-lasting.

Passive Humoral Immunity characteristics

You receive pre-made antibodies.

• Comes from mother or medical treatment.

• No memory cells are formed.

• Protection is temporary.

Active immunity results from

• A. Receiving antibodies from another person

• B. Your own B cells producing antibodies

• C. Receiving antivenom

• D. Maternal antibodies

b

Passive immunity:

• A. Produces memory B cells

• B. Is long-lasting

• C. Uses borrowed antibodies

• D. Requires vaccination

C

Booster shots:

• A. Destroy memory B cells

• B. Intensify the immune response

• C. Provide passive immunity

• D. Prevent antibody production

B

Maternal antibodies provide:

• A. Artificial active immunity

• B. Natural passive immunity

• C. Artificial passive immunity

• D. Natural active immunity

B

What are antibodies also called?

Immunoglobulins (Igs).

immunoglobulins belong to which group of blood proteins?

Gamma globulins.

How many polypeptide chains make up an antibody

four

What type of bonds hold the four antibody chains together?

Disulfide bonds.

How many heavy chains does an antibody have?

Two identical heavy chains

Approximately how many amino acids are in each heavy chain?

400 amino acids

How many light chains does an antibody have?

two identical light (L) chains.

How do light chains compare in size to heavy chains?

they are about half as long

What is the hinge region?

The flexible middle region where the two heavy chains are joined by disulfide bonds.

What is the shape of an antibody monomer?

Y-shaped (or roughly T-shaped).

Where is the variable region located?

At the ends of the heavy and light chains.

What is the function of the variable region?

It forms the antigen-binding site.

Where is the constant region located?

in the stem of the antibody

What determines an antibody's class?

The constant region.

What is the function of the constant region?

It determines how the antibody eliminates antigens and what cells or chemicals it binds.

Give examples of functions determined by the constant region

• Fix complement

• Circulate in blood

• Be present in secretions

• Cross the placenta

What is the structure of IgD?

Monomer

Where is IgD found?

On the surface of B cells.

What is the function of IgD?

Acts as an antigen receptor and helps activate B cells.

What is the function of monomeric IgM?

Serves as an antigen receptor on B cells.

What forms can IgM exist in?

Monomer and pentamer.

Where is pentameric IgM found?

Circulating in blood plasma.

Which antibody is released first during the primary immune response?

IgM

The presence of IgM in the blood usually indicates what?

A current (active) infection.

What are two important functions of IgM?

• Agglutination

• Activates (fixes) complement

What is the structure of IgG?

Monomer

Which antibody is the most abundant in blood plasma?

IgG.

What percentage of circulating antibodies are IgG?

75%-85%

What does IgG protect against?

bacteria, toxins, and viruses

Which antibody is the main antibody of both the primary and secondary immune responses?

IgG

Can IgG activate complement?

Yes

What is the structure of IgA?

dimer

Why is IgA called secretory IgA?

Because it is found in body secretions.

Where is IgA found?

Saliva

• Sweat

• Intestinal juice

• Milk

What is the function of IgA?

Prevents pathogens from entering the body through mucosal surfaces.

What is the structure of IgE?

Monomer.

Is IgE commonly found in the blood?

No. It is almost never found in the blood

Which cells does IgE bind to?

mast cells, and eosinophils

What happens when IgE is activated by an antigen?

Mast cells and basophils release histamine and other inflammatory chemicals.

IgE is primarily responsible for what?

• Allergic reactions

• Inflammation

Blood levels of IgE increase during what conditions?

Allergic reactions

• Chronic gastrointestinal parasite infections