Transcript Immunity and Microbes

Controlling Microbes
Microbes and Society
Different Ways of Controlling
Microbes




Physical
Chemical
Antibiotics
Immunological
Physical Control Methods

Sterilization- destruction of all forms of life

Heat- causes denaturation (unfolding of proteins)
Moist heat- steam, boiling water
 Pressure heat- autoclave, as pressure raises, temperature
raises and sterilization is better achieved

Heat Continued


Pasteurization- a process of using hot water to
destroy most of the heat-resistant microbial
pathogens. Not a sterlization technique as it
does not affect bacterial spores
Dry heat- hot air ovens. Takes a longer time but
effective for powders, oily materials and dry
instruments.
Radiation





Radiation disrupts the nucleic acid components
of a microbe
Ultraviolet (UV)
X ray
Gamma ray
Electron beams
Other Physical Methods




Drying (desiccation)
Disrupt osmotic balance (salting)
Filtration (remember Giardia!)
Refrigeration-slows enzymatic activity, but
doesn’t come near to sterilization
Chemical


Disinfectants- chemicals used to “sterilize”
inanimate objects
Antiseptics- chemicals used to “sterilize”
surfaces of the body
Alcohols and Aldehydes


Ethyl and isopropyl alcohol are two very
important antiseptic/disinfectants
Aldehydes are effective but toxic. Need to be
completely dried before material can be used.
Halogens and Heavy Metals


Iodine and chlorine (halogens) are very good
disinfectants.
Silver, mercury, copper and others are heavy
metals that are good antiseptics/disinfectants.
These are useful metals but are used with
caution as they can be toxic.
Detergents and Phenols


Detergents- wetting agents can lift microbes off
of surfaces for better removal. They can also
cause cell membranes to leak and cause cell
death.
Phenols- good chemical disinfectants. However,
trichlosan (the antibacterial chemical in soaps)
has been implicated in resistance to such
compounds due to overuse.
Antibiotics



Penicillins-group of drugs that act primarily
against Gram-positive bacteria and function
during the synthesis of the bacterial cell wall.
Cephalosporins- a group of antibiotics also
made from mold that also interfere with cell wall
synthesis.
Aminoglycosides- (streptomycin is an example)produced by a soil bacteria and function by
inhibiting bacterial protein synthesis.
Antibiotics Continued


Broad Spectrum- kills numerous types of
microbes (gram Pos, gram neg, rickettsiae,
chlamydiae, and fungi) Tetracycline is the most
prescribed but may be overused (resistance).
Some side effects may be yellowing of the teeth
and stunted bones in children.
Others- erythromycin, vancomycin, rifampin
and more.
Control and Society


We have learned from history that science is not
capable of eradicating infectious disease.
Humans will always fight infections, and they
can use all the weapons at hand to help control
(physical, chemical and antibiotic).
However, the ultimate control relies in the
immune system’s ability to overcome pathogenic
microbes.
Immunological

The defense of pathogens using the immune
system (natural defenses).
The Establishment of Disease







Respiratory Droplets
Dust (aerosols)
Contaminated food or water
Direct contact with contaminated object
Arthropod bites
Contact with animals
Injection with contaminated soil/object
Types of Pathogens





Bacterial
Viral
Parasites
Fungi
Prions
What is Immunity?


A complicated web of cells and chemical signals
that work in concert to protect the body from
pathogens and injury
Cells are educated to distinguish between “self ”
and “non-self ”
Two Branches of Immunity


Innate (Non-specific)
Adaptive
Innate Responses



Physical/Chemical Barriers- skin, pH, mucous
membranes, cilia, sweat glands, others
Microbiogical- Direct competition of good
microbes over bad microbes
Cellular- Phagocytosis, Granulocytes and
Inflammation
Cells without Memory (innate)







Macrophages-very important cell of the immune system. An
antigen presenting cell (APC), phagocytic cell, and recruiting cell
in the inflammatory response
Neutrophils- phagocytic cell that is often the first line of
defense. Short lived but effective.
Dendritic Cells- Professional APC
Mast Cells- tissue dwelling cell, often involved with allergies
Eosinophils- responsible for killing parasites, often involved with
allergies/asthma
Basophils- similar to eosinophils
Natural Killer Cell (NK)- direct cell killing and/or recruiting cell
Inflammation (Innate Response)
Signs of Inflammation



Heat, Pain, Redness, Swelling (calor, dolor,
rubor, tumor).
Cells involved- Macrophages, Neutrophils
Other substances involved- cytokines,
complement
Specific Resistance
(Cells with Memory)

Terminology:
Antigens- chemical substances capable of
stimulating the immune response (mostly proteins)
 Antigenic determinant (epitope)- the small part of
an antigen that the lymphocytes recognize in order
to stimulate the specific response

Cells with Memory


B lymphocytes (B Cells)- differentiate into
antibody secreting plasma cells
T lymphocytes (T Cells)CD4 (T Helper Cells)- help with the inflammatory
response and/or help B Cells make antibodies
 CD8 (Cytotoxic T Cells)- directly kill virally infected
cells

Adaptive Response
Clonal Selection Theory





Random unique receptors confer specificity
Clones
Some clones become memory cells
Response gets better over time (more cells,
faster response, better specificity)
Cells capable of recognizing “self ” molecules
are destroyed.
Cell-Mediated Immunity





Macrophage (or other APC) processes and
presents antigen on MHC class I
CD8 (or Cytotoxic T Cell) recognizes antigen
being displayed on MHC
Clones
Some become effector cells (kills virally infected
cells)
Some become memory cells for the next time
Cell-Mediated Immunity
Effector Cells
Antibody-Mediated Immunity
(Humoral Immunity)






B Cell recognizes (binds to) antigen.
B Cell processes antigen and displays it on MHC class
II
Meanwhile, a macrophage activates a T Cell which
clones itself
T Cell activates B Cell by binding with the MHC
displayed on B Cell surface
T Cell activates B Cell
Some B Cells become plasma cells and secrete
antibodies while others become memory B Cells
Humoral Immunity
Structure of an Antibody
Types of Antibodies
Antibody Isotype Functions





IgG- most abundant in blood/serum. Crosses the
placenta. Found in extracellular fluids.
IgM-first antibody produced, excellent at activating
complement (proteins used in immune reactions)
IgA-protects the mucosal surfaces, passed in breast
milk
IgE-specific for parasitic infections, often seen in
allergic reactions
IgD- receptor on B Cell surfaces
Antibody Functions





Neutralization- neutralizes toxins so they can’t
hurt cells
Opsonization- allows for more efficient
phagocytosis of organisms
Agglutination- clumps non-soluble antigens
Precipitation-forms lattices of antibody and
soluble antigens
Inhibition- keeps pathogens from binding to
receptors and gaining access
Opsonization
Neutralization
Inhibition
Immunity Gone Wrong
Hypersensitivity Reactions

4 Types of Hypersensitivity Reactions




Type I- allergies
Type II- Cytotoxic- antibodies to cell surface antigens
(incompatible blood types or hemolytic disease of the
newborn)
Type III- Immune complex hypersensitivity- accumulation of
immune complexes in blood tissues (Systemic lupus
erythematosus-SLE) or Rheumatoid arthritis
Type IV- Delayed or cellular hypersensitivity- T Cell
mediated, takes 24-72 hours for effects. Poison ivy and other
chemical/skin reactions
Allergy Sensitization
Allergy Elicitation