Nonspecific Defense
Against Disease
Section 33.2
Intro
• Constant exposure to pathogens
• Warm bodies of humans make an ideal place
for pathogens to nest
• Nonspecific defense: first line of defense
• Innate immunity: no recognition of an intruder
that has attacked before
• Human immune system is the most studied
Immunity
• Nonspecific defenses in
immunity include:
• Barriers to entry (skin)
• Protective proteins
• Phagocytes
• The inflammatory
response
Barriers to Entry
• Non chemical and
mechanical barriers:
skin and mucous
membranes
• Ex. Dead cells form
impermeable layer on
skin
• Skin: once injured, there
is possibility of infection
Barriers to Entry
• Mucous of the mucous membranes trap microbes
• Mucous membranes secrete lysozyme (enzyme that
disintegrates bacteria)
• Microbes: bacterium causing disease or fermentation
• Role of upper respiratory tract: ciliated cells sweep up mucous
and particles into the throat
• Regular bacteria residing in intestines also block pathogens
•
Oil glands: contain chemicals that can weaken or kill bacteria
on the skin
• Role of acidic pH in the stomach prevents growth of bacteria
Inflammatory Response
• Inflammatory response: series of events that follows tissue
damage by pathogens
• Signs of an inflamed area: redness, heat, swelling and pain
• Redness and heat is caused by excess blood flow
• Damaged tissue cells release the chemical mediator, histamine
(capillaries dilate, increases blood flow)
• Swollen area stimulates nerve endings, resulting in pain
• Phagocytes (neutrophils and monocytes) squeeze through
capillary walls, enter tissue fluid, ingest pathogens and release
cytokines (stimulate inflammation)
Inflammatory Response
• Most responses are done by dendritic cells, which devour
pathogens and are able to survive
• Cytokines (released by macrophages) stimulate the production
and release of white blood cells (neutrophils)
• Formation of pus: whitish material composed of dead tissue
cells and dead bacteria
• Presence of pus indicates the body trying to overcome and
infection
• Other responses: formation of blood clots which prevent blood
loss in capillaries
• Chronic inflammation: persisting inflammation, controlled by
agents such as aspirin or cortisone
Video
http://www.youtube.com/watch?v=Ue6Yym25N
Wc
Role of the Fever
• Fever: elevated body temperature
• Controversy of fever treatment
• Fever can be responsible for providing an unfavorable
environment for invader
• Increasing body temperature in mice decreased death rate,
shortened recovery time for infections
• Fever can also limit the growth of tumor cells
• Conclusion? An extreme fever should be treated, but mild
cases should be left alone
Phagocytes Role in Defense
• Most white blood cells are phagocytes
• Neutrophils: cells that leave the bloodstream and engulf
bacteria in tissue
• Eosinophils: phagocytic cells which mount attacks against
animal parasites
• Two most powerful phagocytic white blood cells: macrophages
and dendritic cells
• Dendritic cells: found in skin, devour pathogens and stimulate
natural killer cells (lymphocytes)
• Macrophages: found in tissues, stimulate lymphocytes to carry
on specific immunity
Natural Killer (NK) Cells
• Large lymphocytes that kill virus infected cells and cancer cells
through cell-to-cell contact
• Produce cytokines that promote specific defenses
• NK cells congregate in the tonsils, lymph nodes, and the
spleen (stimulated by dendritic cells)
• NK cells look for a self-protein on the body's cells
• If a cancer cell has lost it's self-proteins, the NK cell will kill it
through the use of T cells
• NK cells are not specific, and therefore have no memory
Protective Proteins
• Complement: blood plasma
proteins that "compliment"
immune responses
• Located in blood plasma, but
must be activated by
pathogens
• Can create holes that allow
fluid or salt to enter until the
cell bursts
Protective Proteins
Complement proteins help destroy pathogens by:
• Enhanced inflammation-certain proteins can bind to mast cells
(white blood cell) and trigger histamine
• Binding to surface of pathogens that are already covered with
antibodies
• Form a membrane attack complex that provides holes in the
surface or bacteria and viruses
• Interferons (cytokines) are soluble proteins that affect behavior
of other cells
• Interferons bind to the receptors of non infected cells,
producing substances that interfere with viral replication