Chapter 7
Lymphatic System and
Immunity
Points to Ponder
• What is the connection between microbes and humans?
• What are the parts of the lymphatic system and what are their
functions?
• What are the first and second line of defense in nonspecific
immunity?
• What is cell-mediated and antibody- mediated immunity in the third
line of defense?
• What are the different types of B cells in these processes?
• What is active and passive immunity? Be able to describe how they
are different and give examples of each.
• Understand allergic reactions, tissue rejection, and immune system
disorders as problems that the immune system faces.
7.1 Microbes, pathogens and you
What about the interaction between
microbes and humans?
• Microbes are very abundant in the environment
and as well as in and on our bodies
• We use microbes to make many foods and we
even use them to make drugs
• Microbes are important as decomposers to
recycle nutrients
• Some microbes cause disease in humans; we
call these pathogens
7.1 Microbes, pathogens and you
What are microbes?
• Microbes are microscopic organisms and
particles that include:
– Bacteria
– Viruses
– Prions
– Others (fungi, multicellular parasites, singlecelled protistans)
7.1 Microbes, pathogens and you
How do the sizes of our cells, bacteria and
viruses compare?
7.1 Microbes, pathogens and you
What are bacteria?
•
•
•
•
•
•
Prokaryotic cells
Single-celled
Almost all have a cell wall
Have DNA in a single chromosome
Have ribosomes
Some have accessory rings of DNA called
plasmids
7.1 Microbes, pathogens and you
What are specific structures and shapes
of bacteria?
Bacterial Infections
• Chlamydia.
– Leading sexually transmitted
disease in the US.
• Usually asymptomatic to mild burning
sensation on urination.
– Risk of spreading from the cervix to the
oviducts and into pelvic inflammatory
disease.
» Usually treated with a single dose of
antibiotics.
Chlamydia Eye Infection
Bacterial Infections
• Gonorrhea.
– Affected individuals often have a secondary
infection with Chlamydia.
• Asymptomatic to pain on urination and milky urethral
discharge within 3-5 days.
– Usually cured with antibiotics.
– If a pregnant woman has gonorrhea, she may
give the infection to her baby as the baby
passes through the birth canal during delivery.
This can cause blindness, joint infection, or a
life-threatening blood infection in the baby.
Pelvic Inflammatory Disease
• In women, gonorrhea is a common cause of pelvic inflammatory
disease (PID).
– When symptoms are present, they can be very severe and can include
abdominal pain and fever.
– PID can lead to internal abscesses (pus-filled “pockets” that are hard to
cure) and long-lasting, chronic pelvic pain.
– PID can damage the fallopian tubes enough to cause infertility or
increase the risk of ectopic pregnancy.
– Ectopic pregnancy is a life-threatening condition in which a fertilized egg
grows outside the uterus, usually in a fallopian tube.
• In men, gonorrhea can cause epididymitis, a painful condition of the
testicles that can lead to infertility if left untreated.
• Gonorrhea can spread to the blood or joints. This condition can be
life threatening.
• Some of these complications are also seen in Chlamydia
Secondary Gonorrheal Infection
Bacterial Infections
• Syphilis.
– Three stages.
• Primary stage - Hard chancre
• Secondary stage - Rash
• Tertiary stage - Weakened arterial walls
– Prompt and adequate treatment is critical for control
» Treatment is a form of penicillin
Syphilis
Bacterial Diseases
• Tuberculosis.
– Kills more people worldwide than any other infectious disease.
• Estimated one-third of world’s population is infected.
– Can be treated with antibiotics, but must be consistently taken for
months or years.
• When the disease becomes active, 75% of the cases are
pulmonary TB.
• Symptoms include chest pain, coughing up blood, and a
productive, prolonged cough for more than three weeks.
• Systemic symptoms include fever, chills, night sweats,
appetite loss, weight loss, pallor, and often a tendency to
fatigue very easily
Bacterial Diseases
• Food Poisoning.
– Can be caused by a variety of different
bacteria
• Salmonella.
– Raw chicken
• Botulism
– Improperly canned food
Tetanus
• Tetanus is a medical condition that is
characterized by a prolonged contraction
of skeletal muscle fibers.
• Spasms may occur frequently and last for
several minutes. Spasms continue for 3–4
weeks and complete recovery may take
months.
7.1 Microbes, pathogens and you
What are viruses?
• Small, non-living obligate
parasites
• Must reproduce inside of a
host cell
• Acellular (not composed of
cells)
• All viruses have an outer
protein coat called a capsid
and nucleic acid (RNA or DNA)
inside
• Some viruses have an
envelope
• Viruses are specific to which
cell they will attach to and
enter
Viral Diseases
• Herpes.
– Herpes Simplex Virus Type 1
• Cold sores and fever blisters around the mouth
– Herpes Simplex Virus Type 2
• Herpes infection of the genitals
– Asymptomatic to tingling and itching prior to blistering
– May be reccurring due to stressors. Both type I and type II
viruses hide in nerves until stimulated
» Presently no cure
– Varicella-zoster Virus. Also hides in nervous system
• Causes chicken pox –vaccine is avaliable
• can later remerge as shingles
Genital Herpes
Chicken pox
Viral Diseases
• Measles
– One of most contagious of all human
diseases
• Spread through respiratory route as airborne
particles
• Common Cold
– More than 200 different cold viruses
• Half are caused by rhinoviruses
Smallpox
• Pus-filled bumps (pustules)
• Transmitted by respiratory route
• Easily transmitted and very deadly
• Infect many organs
• Eradicated
Genital Warts
• Human papillomaviruses cause many forms
of warts, including genital warts
– Commonly seen on the penis and near vaginal
opening
• Associated with cervical cancer
– Presently no cure
» Effective treatment relies on various forms of wart
removal
• Vaccine is now avaliable
Prevalence of AIDS
• Pandemic disease.
– Transmitted by sexual contact with an infected
person, needle-sharing, and transfusions of
infected blood.
– Incidence in more-developed countries is
modest, while incidence in less-developed
countries is much higher.
• In sub-Saharan Africa, AIDS affects 9% of adult
population between 15 and 49 years of age.
Phases of an HIV Infection
• Category C: AIDS.
– CD4 T-cell count is below 200 per mm3.
• Lymph nodes have degenerated and patient is
extremely weak and thin.
– Develop opportunistic infection.
» Pneumonia.
» Tuberculosis.
» Encephalitis.
» Kaposi’s sarcoma.
» Invasive cervical cancer.
Other Infectious Agents
• Fungi.
– Molds and yeasts.
• Tineas
– Ringworm
– Athletes foot
– Jock itch
• Candidiasis
– Yeast infections
• Histoplasmosis
– Primarily affects the lungs
– Respiratory disease-chest pains and cough
– Gets worse over years
Protozoans
• Protozoans are generally single eukaryotic
cells with a nucleus and organelles
– Malaria
• Most widespread and dangerous of protozoan
diseases
– Caused by Plasmodium spp
– Toxoplasmosis
• Cat feces, soil, and contaminated meat
• Only serious problem in pregnant women and
people with compromised immune systems.
7.1 Microbes, pathogens and you
What are prions?
• Infectious protein
particles
• Cause degenerative
disease of the
nervous system
• Normal proteins
change their shape
• Mad Cow disease
• Creutzfeldt-Jakob
Disease
7.2 The lymphatic system
4 functions of the lymphatic system
• Lymphatic capillaries absorb excess tissue fluid
and return it to the bloodstream
• Lymphatic capillaries (lacteals) in the small
intestine absorb fats associated with proteins
• Works in the production, maintenance, and
distribution of lymphocytes in the body
• Helps in defense against pathogens
7.2 The lymphatic system
What are the components of the
lymphatic system?
7.2 The lymphatic system
Lymphatic vessels
• One-way valve system that carries fluid called
lymph
• Made of capillaries, vessels, and ducts
• Function to return tissue fluid (includes water,
solutes, and cell products) to the bloodstream
• The larger vessels are similar in structure to
veins and even have valves
7.2 The lymphatic system
Classifying lymphatic organs
• Primary
– Red bone marrow
– Thymus gland
• Secondary
– Lymph nodes and
spleen
7.2 The lymphatic system
Primary lymphatic organs
• Red bone marrow
– Site of blood cell production
– More bones in children have red marrow, and it
decreases as we age
– Some white blood cells mature here
• Thymus gland
– Bilobed gland found in the thoracic cavity superior to
the heart
– Largest in children and shrinks as we age
– Immature T lymphocytes move from the marrow to
the thymus where they mature and 95% will stay
7.2 The lymphatic system
Secondary lymphatic organs
• Lymph nodes
– Small, oval-shaped structures found along the
lymphatic vessels filled B cells, T cells, and
macrophages
– Common in the neck, armpit, and groin regions
• Spleen
– In the upper left region of the abdominal cavity
– Filled with white pulp containing lymphocytes, and red
pulp is involved with filtering the blood
7.3 Nonspecific Defenses
What do the nonspecific defenses
include?
• First line of defense:
– Barriers to entry: physical and chemical
• Second line of defense:
– Phagocytic white blood cells
– Inflammatory response
– Protective proteins: complement and
interferons
7.3 Nonspecific Defenses
The first line of defense
• Physical barriers
– Skin
– Tears, saliva, and urine physically flush out microbes
– Mucous membranes line the respiratory, digestive, reproductive,
and urinary tracts
– Resident bacteria/normal flora that inhabit the body use available
nutrients and space thus preventing pathogens from taking up
residence
• Chemical barriers
– Secretions of the oil glands
– Lysozyme found in saliva, tears, and sweat
– Acidic pH of the stomach and vagina
7.3 Nonspecific Defenses
The second line of defense: Phagocytic
white blood cells
• Includes neutrophils and macrophages
• Both leave circulation and move into tissue
• Cells that are important in the
inflammatory response
7.3 Nonspecific Defenses
The second line of defense: Inflammatory
response
• Four hallmark symptoms are redness, heat, swelling, and pain
• Histamine is released by mast cells causes the capillaries to dilate
and become more permeable to phagocytic white blood cells
• Increased blood flow to an area increases the warmth that inhibits
some pathogens
• Increased blood flow also brings more white blood cells to an injured
area, with neutrophils being the first scouts to kill pathogens
• This response can be short-lived, but if the neutrophils cannot
control the damage, cytokines (chemicals) will call in more white
blood cells including macrophages
7.3 Nonspecific Defenses
Summary of the inflammatory response
7.4 Specific Defenses
What do the specific defenses include?
• Third line of defense:
– Helps protect us against specific pathogens
when nonspecific defenses fail
– Helps protect us against cancer
– Depends on the action of B and T cells
(remember that these are lymphocytes)
T- cells
• T cells begin the immune response
– Come in contact with foreign substance
– Become active
• Some T cells produce chemicals that stimulate more T cells
and B cells
• Others become memory cells
– HIV infects T cells
• B cells: once stimulated by T cells, they:
– Become plasma cells that secrete antibodies
– Others become memory cells
7.4 Specific Defenses
Summary of the types of B and T cells
7.5 Acquired immunity
Immunity
• Is the ability to combat diseases and
cancer
• Can be brought about naturally through an
infection or artificially through medical
intervention
• There are two types of immunity: active
and passive
7.5 Acquired immunity
Active immunity
• The individual’s body makes antibodies against a
particular antigen
• This can happen through natural infection or through
immunization involving vaccines
• Primary exposure is shorter-lived and slower to respond
while a secondary exposure is a rapid, strong response
• This type of immunity is usually long-lasting
• It depends on memory B and T cells
7.5 Acquired immunity
Examples of immunizations: a type of
active immunity
7.5 Acquired immunity
Passive immunity
• An individual is given
prepared antibodies
against a particular
antigen
• This type of immunity is
short-lived
• This can happen naturally
as antibodies are passed
from mother to fetus or
artificially via an injection
of antibodies
7.6 Hypersensitivity reactions
How can the immune system react that
maybe harmful to the body?
• Allergies
• Tissue rejection
• Immune system disorders
7.6 Hypersensitivity reactions
Disorders of the immune system
• Autoimmune diseases:
– A disease in which cytotoxic T cells or antibodies
attack the body’s own cells as if they were foreign
– Examples: multiple sclerosis, lupus, myasthenia
gravis, and rheumatoid arthritis
• Immunodeficiency disease:
– A disease in which the immune system is
compromised and thus unable to defend the body
against disease
– Examples: AIDS and SCID