Infectious Disease and the Immune System. Viruses Viruses are non- living. Only characteristic of living organisms is ability to reproduce. Obligate intracellular.

Infectious Disease Infectious Disease and the Immune and the Immune

SystemSystem

Viruses

• Viruses are non-living.

• Only characteristic of living organisms is ability to reproduce.

• Obligate intracellular parasites.

• Viruses are composed of;– a nucleic acid- can

be dna OR rna. – Protein coat called

a capsid which can be different shapes; helical, polyhedral

– Some viruses have an envelope of lipids that surround the capsid when they leave a host cell

Viruses

• Virus types:– DNA viruses.– RNA viruses.

Viruses

• Retroviruses– RNA core.– Must contain an

enzyme called reverse transcriptase.

– RNA + reverse transcriptase--DNA—inserts into host cell’s DNA—host cells ribsomes make mRNA—Proteins are part of new viruses

Viruses

• Viroids:– Naked RNA that

can replicate.• Prions:

– Infectious proteins.

– Disrupt the cells activities.

Viroids & Prions

Polio virus Influenza Virus

EbolaRabies

Bacteria

• Prokaryotic cells.• Always single cell.• Composed of:

– Cell wall– Cell membrane– Cytoplasm.– DNA that is a

single closed loop– NO membrane

bound organelles

Plasmids

• Some bacteria have a secondary genome called a plasmid.

• Small self replicating DNA that cause disease or make the bacteria resistant to antibiotics

• Some bacteria have a capsule.– Composed of

polysaccharides.– Protects bacteria

from WBCs.

• Bacteria have short hair like structures called pili for connecting to each other and to hosts.

Bacteria

Nonspecific Defenses

Nonspecific Defenses

• Pathogens are disease causing agents.

• Resistance is your bodies ability to defend against pathogens.

• Your immune system gives you resistance.

Koch’s Postulates

• Pathogen must occur in body of organism with the disease.

• Pathogen should be isolated and grown in culture.

• Inoculated animal should develop the disease.

• Same pathogen should be grown in culture.

Identifying Pathogens

Physical Barriers to Disease

• Nonspecific defense.– Sweat, oils, & waxes.– Mucous membranes.– HCL of stomach.

Fever

• Pathogens that attack human body like 98.6 f. best.

• Hypothalamus raising temperature of body increases effectiveness of WBC’s.

• Decreases effectiveness of pathogen.

Proteins

• Interferons– Chemical released by

cells infected by viruses.

– Causes surrounding cells to resist infection.

• Complement Proteins– Circulate in your blood

and become active when they encounter certain pathogens

Inflammatory Response

• Inflammatory response occurs when pathogen penetrates the skin.

• Nonspecific- any pathogen causes an inflammatory response if your skin is broken

Inflammatory Response

• Symptoms:– Redness– Heat– Swelling

pain

Inflammatory Response

• What occurs:– Damaged cells

release histamines.– Causes increase in

permeability.– Causes

vasodialation (swelling)

– Allows phagocytes to digest and destroy foreign matter.

– Phagocytes are drawn towards histamine

Non specific Cellular Defense

• Neutrophils– Most common

phagocyte– Kill pathogens

using phagocytosis.– Circulate in blood

stream.– Migrate towards

site of infection. (chemotaxis)

– Move out of the blood stream (emmigration)

Non specific Cellular Defense

• Macrophages- another type of phagocyte– Stationed in

certain tissues.– Destroy by

phagocytosis.– Rid the body of

debris and damaged cells.

Non specific Cellular Defense

• Natural Killer CellsCytotoxic T Cells

–Attack cells which have been infected by pathogen.–Kills cancer cells.–Kills by puncturing cell membrane.

Day 3

Immune system and recognition of pathogens

How WBCs Recognize Pathogens

• All of your cells are marked as “self” by proteins in your cell membrane.

• Nonspecific WBCs recognize your proteins.

• They leave these cells alone.

• Any cell that does not have “self” markers are attacked.

Summary of Immune System To Date:

• Body has different “lines of defense”.– Barriers

• Skin, mucous membranes, secretions.

– Non specific defenses.• Macrophages, neutrophils, natural killer

cells.• Interferon, compliment proteins.

– Specific defenses.

Specific Defenses

• If pathogens enter the body, the immune system responds.

• Response is to specific pathogens. (Single type)

RBC of different blood type has RBC of different blood type has antigensantigens

Immune System Organs

• Thymus gland• Spleen• Bone marrow• Lymph nodes• Lymphocytes

– B cells– T cells (helper,

cytotoxic)

Immune Responsehow antigens are 1st

recognized by lymphocytes- cell mediated response

• Pathogen has proteins (antigens) on its surface.

• Macrophages destroy pathogen.

• Macrophages present parts of the pathogen (antigen) to helper T cells.

• Macrophages release interleukins

• Interleukins cause– Cytotoxic Killer T cells to

destroy infected cell– Creation of B cells

How Antigens are Recognized

• Lymphocytes then remember the antigen.

• Attack and destroy if in body.

• Cell mediated immune response.

• Antibody and cell mediated immune response are happening at the same time in the body.

Cell Mediated Immune System

• Macrophages present portion of pathogen to B Lymphocyte cells.

• B cells learn pathogen structure and divide into plasma cells and memory cells

• Antibodies are madeBacteria adhering to T lymphocyte.

Antibody Mediated Immune System

• Plasma cells produce proteins called antibodies.

• Antibodies recognize and attach to pathogen.

• Antibodies are Y-shaped proteins.

Antibody Mediated Immune System

• The two arms of the antibody are identical.

• • Antibodies match

proteins of pathogen.

• Actions of antibodies.

Antibody Mediated Immune System

• Primary response occurs the first time exposure to pathogen occurs.

• Secondary response occurs when pathogen invades again.– Faster reaction.– Stronger reaction.– Memory B cells.

Immunity & Vaccination• Naturally acquired active immunity.

– Your are exposed to pathogen in everyday life.

• Naturally acquired passive immunity.– Breast milk.– Mom’s antibodies prior to to birth.

• Artificially acquired active immunity.– Vaccination.

• Artificially acquired passive immunity.– You are given a shot of antibodies.

Brain Pop

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• Immune System ↑

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