Transcript Defense against Disease: White Blood Cells

Blood: The White Blood cell
Review:
• One of the 4 main components of the blood =
white blood cells (leukocytes)
• White blood cells are a major component of your
immune system
• There are many types of WBC’s (macrophages, T
cells, B cells, basophils, etc.)
• Your immune system helps to protect your body
from invaders (bacteria, viruses, etc.)
Challenges for the immune system:
• Constant surveillance and vigilance
• Unpredictable invaders
The Enemy
• Pathogens: microorganisms that are capable of causing
disease.
• An antigen is anything that causes an immune response
1. Viruses
2. Bacteria
3. Fungi
(Remember:. Pathogens carry antigens on their surface but not all antigens
are produced by pathogens. Allergies are caused by the immune system
mistaking antigens present on nonpathogenic substances or organisms
for those of pathogens.)
Public Enemy #1: The Viruses
What they do:
1. The virus docks with receptors on target
(human) cell surface
2. Insert viral DNA or RNA into host cell
3. Use host cell machinery to replicate
many new viruses
4. Lyse (kill) host cell and spread to nearby
cells
• Lytic vs. Lysogenic life cycles
• Examples: smallpox, chickenpox,
polio, HIV, influenza, SARS
Smallpox
Public Enemy #2: Bacteria
What they do:
1. Live in tissues but remain EXTERNAL
to human cells
2. Reproduce rapidly
3. Secrete exotoxins or contain endotoxins
as part of cell wall
• Examples: Escherichia coli,
Clostridium botulinum,
Salmonella, Streptococcus
Figure from Holt Biosources
• Description: Necrotizing fasciitis, commonly
known as Flesh Eating Bacteria (decaying flesh)
is a form of infection generally caused by group
A streptococcus, a variant of the same bug that
causes strep throat
Public Enemy #3: Fungi
What they do:
1. Similar to bacteria- reproduce rapidly
2. Damage cells directly or indirectly by
secreting digestive enzymes. (They want
to eat you!)
3. Also produce toxins. Their purpose is to
keep down the competition – bacteria.
•
Examples: Athlete’s Foot,
Pneumocystis carinii (fungal pneumonia)
So what’s a body to do?
• First line defenses: physical barriers
• 2nd line of defense: Inflammation
So what’s a body to do?
• First line defenses: physical barriers
– skin: a layer of dead tissue that forms an impenetrable
–
–
–
–
barrier
Saliva & tears: contain an enzyme (lysozyme) that
destroys bacteria & viruses
Mucus: in the lining of the respiratory system catches
pathogens. Cilia move the mucus up and out of the RS.
Stomach acid: destroys pathogens that are swallowed.
Fever: raises body temperature higher than pathogens’
ideal and speeds up metabolic rate. Faster metabolic rate
accelerates immune response.
Inflammatory Response
1. At the first sign of injury/invader, nearby cells
and basophils passing by the site of an infection
release a chemical called histamine
2. Histamine causes a dilation of capillaries and an
increase in capillary permeability. This allows
more blood into the area and more WBCs out
into the infected tissues where they can battle
pathogens
3. WBCs battle with pathogen by phagocytosis and
releasing chemical to damage and mark
pathogens
4. This all results in “inflammation” - redness and
swelling
What about when the body attacks itself?
• Autoimmune diseases: When the immune system
mistakes self tissues for non-self (like a pathogen)
and mounts an inappropriate attack.
• Examples:
Wegener's granulomatosis,
multiple sclerosis,
type 1 diabetes mellitus,
rheumatoid arthritis,
lupus
Multiple sclerosis (MS)