Download No Slide Title

Cells
of the
Immune System
And Viral Infections
Cells of the Immune System
• Macrophages
• Helper T cells
• B cells
• Killer T cells
• Memory cells
Immune cells and other blood cells made in bone marrow -- all
are descendents of self-renewing stem cells
Make variable antibodies
Membrane-bound variable T cell receptors
Kill cells that are missing self proteins
Phagocyte
Phagocyte
Note these
are adult
stem cells,
NOT
embryonic
stem cells.
p. 4 “How the Immune System Works” by Lauren Sompayrac
Microbe with protein coat enters
body and starts to reproduce
Immune System
Response to a
Microbial Infection
(viruses & bacteria)
Macrophages circulate thru
body and ingest some of the
microbes, alerting Helper T
cells by presenting protein coat
Helper T cells recognize protein
coat of microbe and alert T and
B cells by making cytokines
Killer T cells kill microbe or
human cells infected with
microbes
B cells make antibodies
that neutralize microbes
Memory T cells remain to
provide immunity
Memory B cells remain
to provide immunity
The Miracle of the Immune System
From birth, humans have the ability
for an immune system response to
any microbial infection but the
response is only initiated when the
infection occurs
After we become sick, why are we
ill for about a week?
After the infection starts, it takes
about one week to make the T cells
and B cells necessary to defeat the
microbe
Viral Infections
Viruses
Based on Harvard Medical
School Family Health Guide
•Viruses do not have
ribosomes and
cannot make their
own protein
•After the virus
attaches to the host
cell’s membrane, it
injects its genetic
material which directs
synthesis of viral
proteins
What Viruses Cannot Do
•
•
•
•
•
•
No metabolism
Cannot reproduce on their own
Cannot move
No respiration
Do not eat
No cellular structures
Viral Infection
• Viruses penetrate epithelial surfaces and take
over cells to produce more viruses
• The host cell then ruptures and releases the
newly produced viruses or the virus will not
rupture the cell until it is stimulated by a
chemical or physical agent.
• Although the immune system can defeat most
viral infections, some viruses can hide from the
immune system and remain in the body
Some contagious viral infections include:
•varicella (chicken pox)
•rubella (German measles)
•the common cold
•hepatitis
•mumps
•infectious mononucleosis
•rubeola (measles)
Antibiotics Don’t Work on viral infections!!!
(and there are not many antivirals)
Lytic Cycle
Lysogenic Cycle
Differences Between Lytic and
Lysogenic Cycles
Lytic Cycle
Lysogenic Cycle
The lytic cycle causes the host
bacterium to undergo cell lysis,
that is, cell destruction.
The lysogenic cycle does not
cause cell lysis or cell
destruction.
The lytic cycle can lead to
production of 100 to 200
progeny phages.
The DNA of the phage gets
integrated into the bacterial
chromosome and no progeny are
produced mostly.
Lysogenic cycle can be
Lytic cycle cannot be converted converted into lystic cycle when
into the lysogenic cycle.
the host cell is exposed to
chemical or physical agents.
Shingles is caused by the chickenpox
virus that has “hidden” in the body
•After having
chickenpox, some of
viruses lie dormant in
nerve cells near spinal
cord
•Years later, the virus
reactivates and travels
along nerve fibers to
skin
•As the virus moves, it
causes pain
•When it reaches the skin,
it causes a rash and
blisters
Based on: Mayo Clinic Health Letter
Why do we keep getting the common cold?
There are over 200
viruses that cause
cold symptoms
Cold viruses can
mutate and change
their health-related
effects
Based on Starr, C. Biology: Concepts and
Applications, Brooks/Cole
The common cold: is a selflimited contagious illness
that can be caused by a
number of different types
of viruses. Spread by
contact.
Transmission: Deposition
of Airborne droplets
•Warts: blister-like bumps
caused by viruses in the
skin.
Transmission: Direct
contact
Severe Acute Respiratory Syndrome
(SARS)
More than 8000
people became
sick worldwide
774 people
died
A New Strain of Lethal Cold Virus?
•Previous virus strains could only survive in the
throat and nasal passages because the
temperature was too high deep in the chest
Viral diseases:
What medication are they treated
with?
•Acquired Immune Deficiency
Syndrome: transmitted sexually
and in blood products, the HIV
virus attacks the Helper T cells of
the immune system, causing
infections that lead to death.
Transmission: Bodily fluids
Influenza:
- we call it the “flu”
- virus mutates quickly so a new
vaccine is offered every year.
Transmission:
Deposition of Airborne droplets
Smallpox:
A deadly disease causing terrible
scars that was wiped out by
widespread vaccination several
decades ago.
Transmission:
Direct Contact
Bacterial
Infections
Bacteria have DNA and ribosomes and
can make their own protein
Based on: Mader, S., Inquiry Into Life, McGraw-Hill
Binary
Fission
1 bacterium
can become
1/2 million in
6-7 hours
Based on Harvard Medical
School Family Health Guide
Bacteria cause…
tuberculosis, syphilis,
gonorrhea, Chlamydia,
Lyme disease, scarlet fever,
Rocky Mountain Spotted
tick fever, staph infection
(MRSA)
TB (tuberculosis)
Lyme Disease-bulls-eye rash
Scarlet Fever
Rash
Nails become ridged
Rocky Mtn Spotted Fever
MRSA (Staph Infection)
Bacterial Infection
• Bacteria penetrate epithelial cells and
undergo rapid division. One bacterium
can become 1/2 million bacteria in 6-7
hours
• Bacteria can produce protein toxins that
kill cells and interfere with nerve and
muscle function
• The immune system cannot respond
rapidly enough to protect the body
against the most dangerous bacteria
Discovery of Penicillin: First Antibiotic
•Fleming happened to observe that petri dishes with
molds had killed bacteria in rings around the mold
•He postulated that the “mold juice” had killed the
bacteria
•The mold was Penicillium notatum and the “juice” was
named Penicillin
Antibiotics
• Antibiotics like penicillin kill bacteria by
blocking cell wall formation
• Antibiotics like penicillin do not kill
human cells because they have no cell
walls
• Antibiotics like penicillin do not work
against viruses because viruses lack
cell walls
E. Coli Outbreaks
E. coli Outbreaks
Swimming
Pool
Cabbage
Patch
Bad
Cheese
Dirty
Toys
What makes this
E. coli strain so bad?
1.
2.
3.
One strain of E. coli has extra genes that allow it to stick to the walls
of the intestine and produce a potent toxin
The toxin injures the cells of the intestinal wall, leading to bleeding
The toxin travels in the bloodstream to the kidneys, leading to kidney
failure
Why is kidney failure life
threatening?
Answer
Because kidneys are responsible for
removal of nitrogenous waste (urea)
and water balance.
Back
Based on: Mader, S., Inquiry Into Life, McGraw-Hill