Viruses are not considered alive as they are not made of cells, do not use energy, and rely on host cells to express their genes and replicate. The immune system has non-specific defenses like skin, mucus, and stomach acid as a first line of defense and the inflammatory response as a second line. The immune system also has specific defenses triggered by antigens on pathogens including antibodies that bind to antigens and mark them for destruction by macrophages. The immune system develops immunological memory allowing a stronger secondary response compared to the primary response. Immune system disorders can include allergies where the immune system overreacts or autoimmune disorders where it mistakenly attacks the body's own cells.

1. Pathogens - Agents ofPathogens - Agents of
DiseaseDisease
Bacteria
Protists
Viruses
Worms
Fungi

2. Viruses are NOT alive!Viruses are NOT alive!
Not made of cells!
Do not use energy
Made of nucleic acid surrounded by a
protein coat
Genes are expressed using the machinery of
the host cell they infect
Head
Tail
sheath
DNA
Tail
fiber
RNA
Capsid
proteins
RNA
Capsid
Surface
proteins Membrane
envelope

3. The Immune System:The Immune System:
Non-Specific DefensesNon-Specific Defenses
1st
line
Skin, mucus, tears, stomach acid
2nd
line – Inflammatory Response
Blood flow increases to site of tissue damage
WBC’s called macrophages ingest and destroy the pathogen
Fever

4. Specific DefensesSpecific Defenses
Immune system response to
ONE PARTICULAR pathogen
Triggered by an antigen on
surface of pathogens
Antibodies bind to antigens
Antibodies mark antigens for
destruction by the
macrophages
Very specific

5. Immunological MemoryImmunological Memory
Primary Immune Response
Secondary Immune Response

6. Immune System Disorders:Immune System Disorders:
Allergies
Overreactions of the immune
system
Mast cells produce histamines
Signals inflammation
Autoimmune Disorders
Immune system mistakenly
attacks its own cells
Type 1 Diabetes, rheumatoid
arthritis