The Lymphatic

System

Chapter 22

Immune System

• Defends body against pathogens (bacteria, viruses, some protists & fungi)

• Distinguishes between self and non-self

• Infectious Diseases – result from the presence of pathogens

• Transmission includes contact with infected individuals/organism, water, food, or airborne inhalation

• Contagious (Communicable) Diseases - infectious diseases capable of being transmitted from one person to another

1. First line of defense (non-specific)

• Skin • Lysozyme = enzyme in saliva, sweat, tears;

attacks bacterial cell walls• Mucus = traps pathogens • Cilia = help clear mucus (and pathogens) from

respiratory tract

2. Second line of defense (non-specific)A. Phagocytic white blood cells (mainly neutrophils

and monocytes) destroy pathogens (phago= eat, cyte=cell)

• Attracted to a site of infection by chemicals released by injured cells (chemotaxis)

B. Inflammation - infected cells release histamine which is a vasodilator, this causes swelling, redness, pain, fever, and it brings WBCs to the area of infection

3rd Line of Defense (specific)

antibody immunity; specific attack on foreign particles

Antigen - foreign protein that triggers immune response

Antibodies (immunoglobulins) - proteins made by lymphocytes; bind to antigens and mark them for macrophage destruction

Lymphocytes - WBCs; two types: B (mature in bone marrow) and T (mature in thymus); both are made in bone marrow

Look at this picture – p. 801

3rd Line of Defense Cont.

1. Primary Immune Response

• First appearance of antigen in the body; memory cells are formed

2. Secondary Immune Response

• Second appearance of antigen; higher levels of antibodies are formed in shorter time; you do not experience sickness due to antibody production from memory cells

Treatment of Infectious Diseases

1. Three lines of defense of the Immune System2. Antibiotics (ONLY FOR BACTERIAL

INFECTIONS!!!)• First antibiotic – penicillin – Alexander

Flemming3. Vaccines• Activate the primary immune response and

formation of memory cells without causing severe disease symptoms

• Typically made from dead/inactive virus or bacteria or their proteins

• First vaccine – smallpox – Edward Jenner

Disorders of the Immune System

• Autoimmune Disorders – body produces antibodies against its own tissue, e.g. Grave’s disease (hyperthyroidism) and rheumatoid arthritis

• Allergies occur when the body reacts to materials which should not be antigenic, e.g. peanuts

Immunity

Active immunityProduction of a person’s own

antibodies; long lasting

Passive immunityAn individual is given antibodies by

another ; short-term (weeks- 6 months)

Natural ActiveWhen pathogen

enters body in the normal way, we make antibodies

Natural PassiveFrom mother in

uterus & breast milk

Artificial PassiveImmunoglobulin

injection;extremely fast, but

short lived (e.g. snake venom)

Edward Jenner

Artificial ActiveVaccination – person makes

antibodies without becoming ill