Genetics of Immunity Part 2

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					Genetics of Immunity Part 2
BIO 2343
Oklahoma City Community College Dennis Anderson

Acquired Immunity
• Slower than 1st and 2nd lines of defense
– May take days – Body has to produce an army of cells and antibodies to fight a specific foreign cell

Cells of the Immune System
All produced in the bone marrow
• Macrophages
– Antigen-presenting cells (APC)
• Show lymphocytes the antigen of a foreign cell

• B cells
– B lymphocytes – Produce antibodies

• T cells
– T lymphocytes – Attack and kill cells directly

Phagocytosis of foreign cell by macrophage

Foreign Cell


Macrophage presents antigen on its surface

• Antigen attached to MHC protein on the surface of macrophage

MHC protein

B Cell receptor attaches to antigen

Foreign Cell Receptor
B cell

Stimulated B cell produces plasma cells. Plasma cells produce antibodies that match antigen of foreign cell

B cell

Plasma cell

Antibodies have several functions
• Some attach to surface of pathogen
– Marks the cell for phagocytosis

• Cell lysis with the help of complement • Agglutinate • Neutralize toxins

Humoral Immunity
Immunity conferred by B cells
• B cells
– Produce plasma cells

• Plasma cells
– Produce antibodies

• B cell must contact antigen before immune system can produce antibodies • Memory B cells
– Remember shape of antigen – Respond very rapidly if foreign cell invades the body again

Cellular Immunity
Immunity conferred by T cells
• Cytotoxic T cells
– Attack infected body cells and cancer cells

• Helper T cells
– Stimulate cytotoxic T cells to work faster – Also stimulate B cells to work faster

• Memory T cells
– Remember shape of antigen

• Suppressor T cells
– Suppress T cell activity when infections subsides

Viruses and Cellular Immunity
• Virus invades a body cell • Virus forces body cell to make new viruses • Virus often kills body cell after it has made new viruses • The life cycle of a typical virus illustrated on the next few slides

Virus Structure
• DNA or RNA
– Genes producing new viruses

• Protein capsid
– Protects nucleic acid inside

• Spikes
– Used for attachment to a cell

Protein Coat


Virus Attaches to Body Cell

Viral DNA Enters Host

Protein coats synthesized from viral DNA instructions

Viral DNA Synthesized

Viruses Exit Cell

Host Cell Killed by Virus

Infected Body Cell
• If the cell is destroyed at this time no new viruses will be made. • The viral protein coat on the cell surface is an antigen

Cytotoxic T cell will connect with foreign antigen on body cell

Cytotoxic T Cell

Cytotoxic T cell releases perforin

Cytotoxic T Cell

Perforin lyses cell to destroy it

Helper T cell connects to antigen on APC

APC releases interleukin I to stimulate Helper T cell

Helper T

Helper T cell releases interleukin-2
• Interleukin II
– 1. Stimulates cytotoxic T cells to be more aggressive – 2. Stimulates B cells to make more plasma cells and therefore more antibodies
Cytotoxic T

Helper T
B cell

Helper T Cells
• Heart of the immune system • Stimulate cellular immunity
– Cytotoxic T cells

• Stimulate humoral immunity
– Antibody production

Antigen-Presenting Cell APC
• Macrophages and other cells • Engulfs and digests foreign cells • Present antigens on MHC proteins to T cells

B Cells
• Lymphocytes that react directly with antigens • Require stimulation from Helper T Cells • Offspring become
– Plasma cells – Memory B cells

• Humoral Immunity

Plasma Cells
• Produce huge numbers of antibodies
– 2000/second

Cytotoxic T Cells
• Activated by antigens on any body cell • Require stimulation from Helper T Cells • Destroys body cells infected with viruses • Destroys cancer cells • Cellular Immunity

Memory Cells
• T Cells and B Cells • Remember antigen • React to a second invasion of an antigen more rapidly

Suppressor T Cells
• Stops T cells and B cells after an infection has been conquered

Types of Antibodies
• IgA---Protects against pathogens at points of entry into body.
– Found in body secretions
• Saliva, urine, tears, milk, mucus

• IgD---Stimulates B cells to make other types of antibodies.
– Found on B cells

• IgE—Attacks parasites, causes allergies.
– Found in body secretions & mast cell tissues

Types of Antibodies (cont)
• IgG---Main antibody to fight against bacteria, viruses and toxins.
– Found in blood and tissues – Crosses placenta to enter blood of fetus

• IgM---Protects the blood. Includes Anti-A and Anti-B for ABO blood group
– Found in blood

THE END Part 2

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