Immunity/Immunology

1. Describe typical external barriers that ward off invading organisms

2. Understand the process of nonspecific inflammatory response

3. Understand how humans recognize and discriminate between self and

non-self tissues.

4. Distinguish between antibody-mediated and cell-mediated patterns of

warfare.

5. Describe some examples of immune failures and identify as

specifically as you can which weapons in the immunity arsenal failed

in each case.

A. Jenner (1796) cowpox could protect against smallpox.

B. Pasteur (d.1896) vaccinations, pasteurization

C. Robert Koch: Discovered the cause of anthrax

A. Pathogen: virus, bacteria, fungi, protozoa, parasitic worms that

cause disease.

B. Surface Barriers to Invasion

1. Intact skin and mucous membranes are barriers

2. Resident bacteria of mucous membranes such as intestine

and vagina deep pathogens in check by outcompeting

them.

3. Lysozymes: enzymes in the mucous membranes attack

bacteria and degrade their cell walls.

4. Enzymes in tears, saliva, and gastric fluid also degrade

pathogens.

5. Urine protects urinary tract (low pH)

C. Nonspecific and Specific response

1. Nonspecific: white blood cells, plasma proteins,

inflammation.

2. Specific: Mounted by lymphocytes, recognize unique

molecular configurations on invading pathogens.

A. 20 Proteins circulate in the blood and can be activated in two ways

1. Can bind to a complex of antibody/antigen

2. Can interact with carbohydrate molecules on the surfaces

of microorganisms.

B: CASCADE effect:

1. Membrane attack complexes become inserted into the

plasma membrane of pathogens causing lysis

2. Chemical gradients of proteins attract phagocytes to the

scene.

3. Complement proteins coat the surface of invading cells—

attracting phagocytes.

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Koch established the

bacterial cause of many

infectious diseases and

discovered the

microorganisms causing

anthrax (1876), wound

infections (1878),

tuberculosis (1882),

conjunctivitis (1883), cholera

(1884)

Mellon/MCHS Name:

A. The roles of Macrophages and White Blood Cells

1. WBC arise from stem cells in bone marrow and can

circulate in the blood or reside in tissue.

2. Three types of WBC act swiftly but are not adapted for

sustained battles:

worms; they also phagocytize foreign proteins and

help to control allergic responses.

vessel permeability.

many foreign agents and do so repeatedly with a big

appetite.

B. The Inflammatory Response

1. Acute inflammation in a besieged tissue allows

phagocytes, complement proteins, and plasma proteins to

escape from the blood.

2. Physical signs include redness, swelling heat, and pain

3. The progression of inflammation is as follows:

a. Tissue irritation causes mast cells (a basophil) to

release histamine and other substances which

cause the blood vessels to become engorged and

capillary walls to become “leaky.”

b. Within a few hours, neutrophils and macrophages

leave the blood vessels to begin engulfing foreign

materials.

c. Macrophages release interleukin-1, which signals

other white blood cells, allows body temperature

to rise (further enhancing defense mechanisms)

and causes conservation of body energy due to

drowsiness.

d. Clotting mechanisms help wall off the pathogen

and promote repair of tissues.

Summarize the progression of

inflammation:

4. Define the following terms: Complement proteins,

Neutrophils, Eosinophils Basophils, Macrophages

Mellon/MCHS Name:

IV. The Immune System

A. Defining features

1. Sometimes physical barriers and inflammation may not be

sufficient to overwhelm the invader.

a. Vertebrate immune system is a complex interaction of two

types of white blood cells called B and T lymphocytes.

b. This system displays both specificity and memory.

2. Each kind of cell, virus, or substance bears unique molecular

configurations that give it a unique identity.

a. Your own cells (self) bear surface proteins which your

lymphocytes ignore.

b. Nonself markers from viruses, bacteria, bee venom, organ

transplants, etc. bear antigens that trigger immune responses.

c. When B and T lymphocytes encounter a nonself marker,

they divide repeatedly.

1. Some become effector cells, which will engage and

destroy the enemy.

2. Others are memory cells that will be called upon later if

the invader strikes again.

3. Immunological memory and specificity involve three events:

a. recognition of a specific invader

b. repeated cell divisions to form huge populations of

lymphocytes

d. differentiation into subpopulations of specialized effector

and memory cells.

B. Antigen-Presenting Cells—Triggers for immune response

1. Any nonself marker that triggers the formation of

lymphocytes is an antigen; the antigen binding receptors

are antibodies, secreted by B cells.

2. MHC markers reside in the plasma membranes of body

cells; some are unique to your lymphocytes and

macrophages.

3. Macrophages can digest bacterial invaders but not their

antigens, which become attached to MHC molecules to

form antigen-MHC complexes

4. When antigen fragments and a certain MHC marker are

displayed together at the cell surface, lymphocytes respond

by dividing to produce huge numbers of lymphocytes.

C. Key Players:

1. Helper T cells produce and secrete chemicals that promote

formation of large populations of effector and memory cells.

2. Cytotoxic T cells kill body cells that have either become infected

with intracellular parasites or are identified as tumor cells. (cell

mediated immune response)

3. B cells are lymphocytes that produce antibodies. (antibody

mediated immune response.

Mellon/MCHS Name:

D. Control of Immune Responses

1.When antibodies have "saturated" the binding sites on pathogens, fewer

exposed antigens translates into less production of antibodies.

2.Inhibitory signals from cells with suppressor functions shut down the

immune response.

V. Lymphocyte Battlegrounds

A. The antigen-presenting cells and lymphocytes interact in lymphoid

organs (tonsils, adenoids), lymph vessels, and lymph nodes.

B. In lymph nodes, cells are organized for maximum effectiveness with

antigen-presenting cells in the front line, engulfing invaders.

VI. Cell-Mediated Responses

A. T Cell Formation and Activation

1. T cells arise from stem cells in the bone marrow, then travel to the

thymus gland where they differentiate into helper T and cytotoxic T

cells and acquire receptors for MHC markers and antigen-specific

receptors.

2.Virgin T cells ignore both unadorned MHC markers and free

antigen but do bind antigenMHC complexes on presenting cells,

which stimulates division of the T cells to form clones.

B . Functions of Effector T Cells

stimulate cell divisions of virgin T cells and virgin B cells.

cells and tumors and kill the cells by secreting perforins that punch

holes in the cell membranes.

C. Natural Killer Cells

and infected cells.

2.They do not require an antigen-MHC encounter.

VII Antibody-Mediated Responses

A. B Cells and Targets of Antibodies

1. B cells also arise from stem cells and eventually produce copies

of a specific antibody.

a. Antibodies are proteins with binding sites for a single antigen.

b. The Y-shaped antibody is embedded in the B cell membrane

with the two arms extending as antigen receptors.

2. When its receptors lock onto an antigen, the B cell will undergo

repeated cell divisions IF there are also present secretions from a

helper T cell already activated by the same antigen.

3. The clonal B cells differentiate into effector (formerly known as

plasma) cells and memory cells; effector cells produce antibodies

that recognize antigens and mark their possessors for destruction by

phagocytes.

4. The main targets of antibody-mediated responses are extracellular

pathogens and toxins.

B . Immunoglobulins

1. All five classes of antibodies have binding sites for antigen but the ones in

each class have special sites for specific functions.

2. The different classes are the protein products of gene shufflings:

a.IgM antibodies set the complement cascade in motion and bind

invaders into dumps.

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b.IgG antibodies neutralize toxins, are long lasting, can cross the

placenta, and are found in mother's milk.

c.IgA antibodies are present in the mucus of respiratory, digestive,

and reproductive tracts.

d.IgE antibodies bind to basophils and mast cells where they act as

traps for antigen.

IX. Immune Specificity and Memory

A. Formation of Antigen-Specific Receptors

1. Immunological specificity lies in DNA recombinations.

polypeptides in each arm of the antibody molecule.

into millions of combinations to produce antibodies against

numerous agents.

2. The clonal selection theory proposes that a lymphocyte activated

by a specific antigen will divide and give rise to a clone of cells that

are specific only to that antigen.

B . Immunological Memory

1. Immunological memory of a primary immune response is

explained by the clonal selection theory.

2. Some B and T memory cells will continue to circulate for years

and make secondary response to any subsequent encounter of the

same antigen.

3. This later response will be more rapid, greater, and of longer

duration than was the primary immune response.

X. Immunization and Other Practical Applications of Immunology

A. Immunization

1. Immunization involves a deliberate production of an immune

response and memory cells.

a.In active immunization, the first dose of vaccine elicits a

primary immune response; a second dose ("booster") elicits a

secondary, and more long-lasting, response.

b.Passive immunization involves injections of antibodies to

persons already infected with pathogens.

2. A vaccine can be made from killed or weakened pathogens,

inactivated toxins, or genetically engineered viruses.

B . Monoclonal Antibodies

1. Monoclonal antibodies are obtained by techniques that produce

large quantities of antibody from B cells.

a.A mouse is immunized with a specific antigen; B cells are

extracted and fused with cancerous cells known as myeloma

cells to produce a hybridoma cells.

b.The hybridoma cells produce the desired antibody

indefinitely.

2.Monoclonal antibodies are being used commercially in home

pregnancy tests, screening for prostate cancer, and passive immunity.

C. Cytokines

1.Signaling molecules produced by lymphocytes are called

cytokines.

2.Tumor necrosis factor secreted by cytotoxic T cells has been used

experimentally to treat malignant melanoma of the skin.

3.Interferons have been used to suppress viral diseases.

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