CHAPTER 43

THE BODY’S DEFENSES

• VirusesViruses• BacteriaBacteria• ProtozoanProtozoan• FungiFungi• AnimalAnimal• ParasitesParasites

Any microbes (organism or virus) that cause disease

Including: Viruses Bacteria Fungi Protozoa Flatworms Roundworms

Considered Non-Living Two Parts:

A Capsid: protein coat A Nucleic Acid: DNA or RNA

Function: Reproduction (Replication,

actually) Method: Hijack a living host cell and

use it’s cellular machinery to replicate and build new virus particles.

HIV

Ebola

HIV: Human Immunodeficiency Virus Targets T-Cells (Immune Cells)

Influenza Rhinovirus Small Pox Polio Ebola, Marburg, Hantavirus Herpes (different simplexes)

Most are not pathogenic (major decomposers, major photosynthesizers, critical components for many ecosystems)

All prokaryotic, unicellular Parasitic strains and those that produce

toxic byproducts are pathogenic Most pathogenic varieties form colonies

and can be grown on TSA plates

Escherichia coli Staphylococcus aureus

Cocci: Staphylococcus (Staph), Streptococcus (Strep Throat)

Bacilli: Escherichia coli (E. coli; 0157:H7), Bacillus anthracis (Anthrax), Clostridium botulinum (Botulism Toxin Producer)

Spirilla: Campylobacter jejuni (causes diarrhea esp. in children), Helicobacter pylori (causes peptic ulcers)

Decomposers that occasionally don’t wait until an organism is dead to feed on it

Examples: Valley Fever (lung), Ringworm (skin), Athletes Foot (skin)

Most are surface/epidermal, some (rarely) become invasive

Protozoa are unicellular animal-like protists (motile)

Pathogenic examples include: Giardia Cryptosporidium Trypanosoma

Many have insectvectors

Giardia

Flatworms belong to a group called platyhelminthes

Many are parasitic Examples include:

Tapeworms Flukes (liver fluke) Schistosoma

Direct Contact: Person to person – Kissing Shaking hands Touching open wounds or sores Sexual contact – body fluids

Indirect Contact: Objects – doorknobs, telephones, ect... Air (tuberculosis) Food (botulism) Water (typhoid fever) Vectors

Animal Bites – disease to organism to humans (rabies, West Nile virus)

Portals of Entry Respiratory Tract – nose, mouth, lungs Gastrointestingal Tract – throat,

stomach, intestines Mucous Membranes – nose, eyes, etc. Penetration – bites, cuts, injections

• Utilization of host nutritional Utilization of host nutritional resourcesresources

• Physical damage to host tissuesPhysical damage to host tissues• Production of toxic substancesProduction of toxic substances• Chromosomal and gene damageChromosomal and gene damage• Body cells behave abnormallyBody cells behave abnormally

Defense MechanismsDefense Mechanisms

1. First Line of Defense2. Second Line of Defense3. Third Line of Defense

• Skin acts as barrier to microbes and viruses- sweat has a low pH

• Mucus traps foreign particles• Tears

- Lysozyme has antimicrobial action• Gastric stomach acid

11stst Line of Defense Line of Defense

sebaceous glands

sweat gland

epidermis

mucus

cilia

columnar epithelium

• Phagocytic cells • N M E B- Natural Killer (NK) Cells: attack virus

infected cells• Inflammatory Response• Antimicrobial proteins

- Lysozyme- Interferon- Antibodies

22ndnd Line of Defense Line of Defense

NeutrophilsMonocytesEosinophils

NeutrophilsMonocytesEosinophils

Mechanism of PhagocytosisMechanism of Phagocytosis

MacrophageMacrophage

Lymphatic System

Inflammatory ResponseInflammatory Response

Histamine & prostaglandins released

Capillaries dilateClotting begins

Chemotactic factors attract phagocytic cells

Phagocytes consume pathogens & cell debris

IMMUNITYIMMUNITY

There are 2 types of lymphocytes: B Lymphocytes T Lymphocytes

Mostly concentrated in: Spleen Lymph nodes Other lymphatic tissue

Known as specific

Antigen: A specific molecule that triggers a specific response by lymphocytes.

Antigen: antibody-generator Found in surface of cell membranes B cells and T cells attack different types

of antigens They recognize d B cells secrete antibodies

Lymphocyte Formation

During maturation: Antigen receptors are tested Antigen receptors specific to innate body

molecules are inactive or destroyed (apoptosis)

Only lymphocytes that react to foreign material are left

Failure of self-tolerance leads to auto immune diseases Multiple sclerosis

Primary immune response (10-17 days) Secondary immune response (2-7 days) Immunological memory

• Active Immunity- Naturally-Acquired Active Immunity- Artificially-Acquired Active Immunity

• Passive Immunity- Naturally-Acquired Passive Immunity- Artificially-Acquired Passive Immunity

The production of antibodies against a specific disease by the immune system.

Naturally acquired through disease Artificially acquired through vaccination

Vaccines include inactivated toxins, killed microbes, parts of microbes, and viable but weakened microbes.

Active immunity is usually permanent

A vaccinated person has a secondary response based on memory cells when encountering the specific pathogen. Routine immunization against infectious

diseases such as measles and whooping cough, and has led to the eradication of smallpox, a viral disease.

Unfortunately, not all infectious agents are easily managed by vaccination. HIV vaccine in the works

Passive Immunity- Protection against disease through antibodies produced by another human being or animal.

Effective, but temporary Ex. Maternal antibodies Colostrum.

Passive immunity can be transferred artificially by injecting antibodies from an animal that is already immune to a disease into another animal. Rabies treatment: injection with antibodies

against rabies virus that are both passive immunizations (the immediate fight) and active immunizations (longer term defense).

Humoral Immunity• Involves antibodies (secreted from B

cells) dissolved in the blood plasma.• Demonstrated as a immune response

using only the blood serum.• Defense against bacteria, bacterial

toxins, & viruses.

Cell-Mediated Immunity• Involves the activities of specific

white blood cells (T cells).• Defense against cancer cells, virus-

infected cells, fungi, animal parasites, & foreign cells from transplants.

• Mature in bone marrow• Involved in humoral immunity• Once activated by antigen,

proliferate into two clones of cells: plasma cells that secrete antibodies and memory cells that may be converted into plasma cells at a later time

antibodies

B Cells

antigen

plasma cells memory cells

antibodies

time (days)

antib

ody

conc

entr

atio

n

first exposure to antigen A

time (days)

antib

ody

conc

entr

atio

n

first exposure to antigen A

primary response: concentration of anti-A antibodysecond exposure

to antigen A

time (days)

antib

ody

conc

entr

atio

n

secondary response: concentration of anti-A antibody

second exposure to antigen A

first exposure to antigen B

time (days)

antib

ody

conc

entr

atio

n

primary response: concentration of anti-B antibody

first exposure to antigen B

Antibodies constitute a group of globular serum proteins called immunoglobins (Igs). A typical antibody molecule has two identical

antigen-binding sites specific for the epitope that provokes its production.

antigen binding sites

antigen

light chains heavy chains

• Precipitation of soluble antigens• Agglutination of foreign cells• Neutralization• Enhanced phagocytosis• Complement activation leading to cell lysis• Stimulates inflammation

The binding of antibodies to antigens to form antigen-antibody complexes is the basis of several antigen disposal mechanisms.

The classical complimentary pathway, resulting in lysis of a target cell

Immunoglobin ClassesImmunoglobin Classes

IgM• 1st response to antigen• Effective in agglutination• Can’t cross placenta

IgG• Most common form• Crosses blood vessels• Crosses placenta

(passive immunity to fetus)

IgA• Secreted from mucus

membranes• Prevents attachment of

bacteria to epithelial surface• In colostrum

IgD• B cell activation• Can’t cross placenta

IgE• Histamine

reactions and allergies

Overview of Immune System Responses

• Mature in thymus• Involved in cell-mediated immunity• Activated when another cell

presents antigen to them• Several types of T cells: cytoxic T

cells, helper T cells, suppressor T cells, and memory T cells

• There are two main types of T cells, and each responds to one class of MHC molecule.– Cytotoxic T cells (TC) have antigen receptors

that bind to protein fragments displayed by the body’s class I MHC molecules.

– Helper T cells (TH) have receptors that bind to peptides displayed by the body’s class II MHC molecules.

T Cells

perforin

pores in target cell

interleukin 1macrophage

helper T cell

bacteriumbacterialantigens

T cell receptor

The central role of helper T cells

The central role in Helper T cells in an infected cell

Malfunctions of the immune system can produce effects ranging from the minor inconvenience of some allergies to the serious and often fatal consequences of certain autoimmune and immunodeficiency diseases.

• Autoimmune Disease• Allergy• Immunodeficiency

• Rheumatoid arthritis• Type I Diabetes• MS• Lupis• Crohn’s disease• Grave’s disease

PhenotypePhenotype GenotypeGenotypeOO i ii iAA I I A A I I AA or I or I A A

iiBB I I B B I I BB or I or I B B

iiABAB I I A A I I BB

ABO Blood TypesABO Blood Types

Produces Produces anti-B anti-B antibodiesantibodies

b

b

b

b

b

b

b

b

ABO Blood TypesABO Blood Types

Produces Produces anti-A anti-A antibodiesantibodies

a

a

a

a

a

a a

a

aa

ABO Blood TypesABO Blood Types

Produces neither anti-A nor anti-B antibodies

ABO Blood TypesABO Blood Types

Produces Produces both anti-A both anti-A and anti-B and anti-B antibodiesantibodies

a

a

a

a

a

aa

a

aa

b

b

b

b

b

b

b

b

RH- indicates no protein

RH+ indicates protein

15% of population is RH-

Rh+ mother w/Rh- baby– no problemRh- mother w/Rh+ baby– problemRh- mother w/Rh- father– no problemRh- mother w/Rh- baby-- no problem

RhoGAM used @ 28 weeks

• Hypersensitive response to certain environmental allergens

• Food, pollen, pet dander, asthma, bee sting

• Anaphylactic shock - epinephrine

Mast cells, IgE, and the allergic response.

AIDS

Acquired Immunodeficiency Syndrome

HIV (virus) attacks T-cells

Weakens or eliminates immune system

Susceptible to many fatal diseases

ProblemsProblems

Transmission of HIV requires the transfer of body fluids containing infected cells, such as semen or blood, from person to person. Unprotected sex Nonsterile needles HIV transmission among heterosexuals is

rapidly increasing as a result of unprotected sex with infected partners.

HIV in Africa and Asia- primarily by heterosexual sex

• In 1983, a retrovirus, now called human immunodeficiency virus (HIV), had been identified as the causative agent of AIDS.

With the AIDS mortality close to 100%, HIV is the most lethal pathogen ever encountered. Molecular studies reveal that the virus probably

evolved from another HIV-like virus in chimpanzees in central Africa and appeared in humans sometimes between 1915 and 1940. These first rare cases of infection and AIDS went

unrecognized.

HIV Testing:

The HIV antibody test has be used to screen all blood supplies in the U.S. since 1985. May take weeks or months before anti-HIV

antibodies become detectable.

- Drug treatment available- Best prevention is education and protected sex