Biology I

Chapter 39 Immunity from Disease

KEY!

Disease- condition caused by a pathogen in which a system, organ, or tissue is not

   functioning properly.

 

Pathogen- any agent that causes an infectious disease

-         all produce toxins (poisons) that interrupt normal cell function

-         can be caused by: 

1. bacteria                   

2. virus            

3. fungus

4. Protozoans              

5. invertebrates

 

Immune System- complex set of reactions the body uses against pathogens.

                                     (the response to a foreign substance)

 

Robert Koch- German scientist – was first scientist to identify pathogens

·        ____________ = first pathogen identified

·        Koch’s POSTULATES

                 1.

                 2.

p.1025      3.

                                         4.

                                    Exceptions ----

                       

Louis Pasteur- scientist, whose work on chicken pox virus (varicella) opened the field              

                          of microbiology.

 

Infectious Disease- one that is caused by a pathogen and can be spread from host to  

                                  host.

 

 

Methods of Disease Transmission  (infection)

 

  1. Air – colds, flu
  2. Water & Food – all food poisoning, Amebic dysentery
  3. Arthropod Vectors – lice, ticks, fleas, flies, mosquitoes
  4. Human contact (direct) – STD’s, impetigo

  (indirect) – towels, dishes

  1. Human immune carriers – “Typhoid Mary”

 

Endemic -

 

Epidemic -

The Body’s Defense System

 

I.                     Nonspecific Defenses  -- act the same way against all diseases regardless of nature of organisms causing it.

A.     Mechanical and Physical Barriers

1)      Skin – 1st line of defense

2)      Sweat, Oils, Waxes: contain poisons such as lactic acid.

3)      Mucous Membranes: in mouth and nose, trap microorganisms.

4)      Saliva and Tears: contain lysozyme, an enzyme that destroys bacteria.

B.     Chemical – defenses used after pathogen has entered body.

1)      Digestive Acids – hydrochloric acid.

2)      Interferons – proteins that trigger the production of an enzyme that enables a cell to recognize a virus and prevent it from reproducing.

3)      Complement – group of proteins in blood that attach to pathogen and help destroy them.

4)      Inflammation – reaction by tissues to an injury; produced by white blood cells (leukocytes)

Causes: swelling, pain, heat, pus

5)      Phagocytosis – white blood cells, leukocytes, engulf pathogen and raises temperature

Types of leukocytes

a)      neutrophils – WBC’s with irregular nuclei that ingest small numbers of bacteria.

b)      macrophages – large WBC’s that engulf large numbers of bacteria.

c)      basophyl

d)      lymphocyte

e)      eosinophil

 

fever – a symptom not a disease.

 

                                          Pus – a thick fluid containing;

1.   dead leukocytes

2.   platelets

3.      lymph

4.      dead bacteria

 

 

II           Types of Specific Defenses

 

Specific Defenses are cells or proteins produced by the body in response to an antigen

 

 Antigen – any foreign protein substance

                             

                               Antibody – cells the body produces to destroy antigens

 

 Lymphocyte – special WBC’s that exist as T-Cells and B –Cells

 

                              T-Cells – attack the antigen directly

B-Cells – produce chemicals that leave antigens

    harmless

 

1)      Primary Immune Response – develops in the bone marrow but differentiate in either the Thymus Gland (T-Cells) or the Bone Marrow (B-cells).

 

a)      Helper T-Cells  -  Distinguishes self from non-   

                                      self.

 

b)      Memory T-Cells – T-cells that stay in the blood to provide an early response to new invasions of an antigen.

 

c)      Antibodies –  Y-shaped proteins that are made by B-cells; they bind to and mark them for death.

 

2)      Secondary Immune Response – reaction to a new invasion by the same pathogen.

 

a)      Memory T- and B-Cells-  reproduce quickly and fight infection

b)      Killer T-Cells – bind and kill cells to release pathogens

c)      Suppressor T-Cells – T-cells that stop B-cells from producing antibodies when the infection is over.

III         Immunity and Immune Disorders

 

Immunity – ability to resist diseases

a)      Natural Immunity – present at birth (inborn)

b)      Acquired Immunity – gained by vaccination, breast feeding or by having the disease

 

                              Immune System Disorders

 

1.      Allergy – reaction to harmless allergens – such as foods or pollen caused by suppressor cells not preventing B-cells from producing antibodies. This allows the allergens to bind with antibodies and release histamines – chemicals that cause sneezing, watery and itchy eyes and wheezing; produced by mast cells.

2.      Autoimmune Disease- immune system produces misreads its own cells as antigens and destroys them.

a.)    Lupus – breaks down blood vessels, heart and liver

b.)    Rheumatoid Arthritis – joints swell and disfigure

c.)    Addison’s Disease – lack adrenal hormone, causes nausea, vomiting, fatigue and skin disorders

3.      Acquired Immune Deficiency Syndrome -AIDS– caused by a virus that enters a T-4 cell and becomes part of its chromosomes and rides along on its membranes undetected by antibodies possibly for up to 10 years. Secondary infections of AIDS patients such as Kaposi’s Sarcoma and Pneumonia cause death.