Path 4

CD4+ Cells

T Helper Cells

CD8+ Cells

T Cytotoxic cells

Roles of T Helper cells

1. Activate B cells to release Abs

2. Activate T cytotoxic cells

3. Help ramp up macrophage activity

4. Send chemical messengers (cytokines)

How are T Helper cells activated?

By APCs

List lymphoid structures

Lymph nodes and vessels, bone marrow, thymus gland, spleen, tonsils, Peyer's patches

Features of complement proteins

- Produced by liver

- Concentration does not fluctuate

- Fixation to microbes results in cell lysis

- Flagged by Abs

- Part of INNATE immunity

Autoimmunity

A disorder in which your immune system cannot distinguish Self from Non Self

IgM

- Early stage immune response

- Found attached to B cells ( as antigen receptors)

- Found in blood

- Concentration drops if no longer exposed to antigen

IgG

- Follows IgM secretion

- Secreted for longer periods

- Most common Ab found in blood

- Only Ab capable of crossing placenta

- Concentration drops if no longer exposed to antigen

IgE

- Triggers in allergic response, causes histamine release from basophils and mast cells

- Triggers in parasitic response

IgD

Trick question! The mysterious antibody,

IgA

- Found in secretions and in mucous membranes

How do antibodies do their job?

Agglutination

Precipitation

Neutralization

Complement fixation

Where are macrophages and dendritic cells found?

All over, in circulation

Where are T cells and B cells found?

In lymphatic tissue

What is the humoral immune response?

B cells

What is the cell mediated immune response?

T cells

What is a plasma B cell?

A B cell that has been exposed to an antigen and is conditioned to make an antibody.

Do B cells target extracellular microbes or intracellular microbes?

Extracellular

What does HIV target?

T Helper cells (CD4+)

What is normal CD4+ : CD8+ ?

2 : 1

Where is MHCI found?

The surfaces of all nucleated cells

What does MHCI present?

Intracellular peptide fragments

Where is MHCII found?

Surfaces of specialized cells: Dendritic cells, macrophages, B cells

What does MCHII present?

Extracellular peptide fragments

What is an epitope?

A distinctive portion of a protein (marker) on an antigen that triggers an immune response

What is serum?

The component of blood that is NOT a blood cell or a clotting factor

What does serum contain?

Non-clotting proteins, electrolytes, antibodies, hormones, as well as any antigens or microbes or drugs

What is a titer?

A measurement of how much antibody is present (in serum) that recognizes a particular epitope

What are effector cells?

Short lived cells that are produced in response to an exposure.

How long does a primary exposure take to reach peak effector cell response?

10-14 days. Sometimes as long as 21.

How long does it take a secondary exposure to reach peak effector cell response?

2-7 days.

How long does vaccine induced immunity typically last?

2-10 years

Allograft

Tissue transplanted between two genetically distinct members of the same species

Isograft

Tissue transplanted between two genetically identical bodies (identical twins)

Autograft

Tissue transplanted from two parts of the same body

Xenograft

Tissue transplanted between members of two different species

What are factors that increase the chances of successful transplantation?

1. HLA is an excellent match

2. Donor is living and in good health

3. Immunosuppressive drugs taken regularly

What types of transplantations do not have risks of rejection?

Cornea and connective tissue (heart valve)

Host vs Graft: hyperacute response

Occurs within minutes. Results in systemic inflammatory response and rapid RBC clumping.

Host vs Graft: Acute response

Will occur to an extent in all transplants unless immunosuppression is achieved. Risk is highest within first three months.

Host vs Graft: Chronic repsonse

Occurs over months or years, results in gradual degeneration of vessels.

GVHD usually involves which three organs/systems?

Skin, liver, GI tract

In what situation may GFDH be beneficial to the recipient?

Leukemia patients \>>> transplanted T cells may attack leukemia cells

What are the three most common immunosuppressive drugs?

Cyclosporine, azathioprine, prednisone

What is the risk of taking cyclosporine?

Kidney damage

What are examples of Type I hypersensitivity reactions?

Hay fever, asthma, anaphylaxis, skin rashes

What are common drug allergies?

Penicillin, sulfa, local anesthetics

What happens during Type I hypersensitivity reactions?

- B cells produce IgE

- IgE binds to mast cells and basophils

- These cells release histamine, leukotrienes, and prostaglandins

- Results in vasodilation and smooth muscle contraction

What results in a type I hypersensitivity reaction if sensitized B cells are in the nasal mucosa?

Hay fever

What results in a type I hypersensitivity reaction if sensitized B cells are in the respiratory mucosa?

Asthma

Do symptoms appear during the first exposure of an allergen?

No, first exposure causes sensitization. Secondary exposure results in symptoms.

What do mast cells do during cases of anaphylaxis?

Dump huge amounts of chemical mediators into the bloodstream

How is anaphylaxis remedied?

Epinephrine injection

Signs and symptoms of anaphylaxis

Coughing, dyspnea, weakness, dizziness, edema, loss of consciousness. Results from systemwide vasodilation, severe drop in BP and brnchoconstriction.

What do epinephrine injections do?

- Vasoconstrictions

- Increases heart rate

- Relaxes smooth muscle around airways

- Stops release of chemical mediators

Vasculitis

Inflammation of blood vessels

Induration

Hardening of the skin as a result of inflammation

When are antihistamines useful?

In the early stages of an allergic reaction. They block the tissue response to histamine.

What is a type II hypersensitivity reaction?

Cytotoxic hypersensitivity

- Antigen presented to B cell by APCs

- Antibodies generated

What are examples of type II hypersensitivity reactions?

Hemolytic reactions, ITP, acute graft rejection, type I diabetes mellitus

What is a type III hypersensitivity reaction?\>

Immune Complex Hypersensitivity

- Insoluble antibody/antigen complexes are created

- Pain, swelling, edema, induration, hemorrhage, possibly necrosis

What are examples of type III hypersensitivity reactions?

Lupus, post-strep glomerulonephritis, serum sickness (from non-human injections), arthus reactions (from vaccines

What is a type IV hypersensitivity reaction?

Delayed hypersensitivity reaction (DTH)

- T cells are sensitized after first exposure to antigen

- Effector phase: subsequent exposures cause T helper cells to secrete cytokines

- Macrophages, T helped cells, and cytokines get into a funky positive feedback cycle

- This cycle is supposed to destroy the antigen, but can damage tissue too

What are examples of type IV hypersensitivity reactions?

Poison ivy, latex allergy (contact derm) M. tuberculosis

Name the four types of hypersensitivity reactions?

I: Allergic reactions (hay fever, asthma)