Download Chapter 1 Notes - Social Circle City Schools

Chapter 43 Notes
The Body’s Defenses
Nonspecific Defenses
Against Infection
The skin and mucous membranes provide
first-line barriers to infection
-skin prevents the entry of pathogens
- mucous membranes line digestive and
respiratory tracts
- the skin also secretes acids and
chemicals
- lysozyme: digests the cell wall
Nonspecific Defenses
Against Infection
Phagocytic cells, inflammation, and
antimicrobial proteins function early in
infection
Mechanisms depend mainly on
phagocytosis: the ingestion of
invading organisms by certain types of
white cells
Nonspecific Defenses
Against Infection
- neutrophils: make up 60-70% of
WBC; engulf and destroy invaders
- monocytes: more effective; develop
into macrophages (“big eaters”); will
fuse with a lysosome that will release
hydrolytic enzymes
- natural killer (NK) cells: destroy
virus-infected body cells
Nonspecific Defenses
Against Infection
Nonspecific Defenses
Against Infection
Nonspecific Defenses
Against Infection
Damage to tissue triggers a localized
inflammatory response
- cells release histamine causing
dilation of vessels
- increased blood supply, due to
dilation, causes redness and warmth
- blood flow also brings large numbers
of phagocytes to the infected area
Nonspecific Defenses
Against Infection
How Specific Immunity
Arises
Lymphocytes provide the specificity and
diversity of the immune system
Two main types: B lymphocytes (B
cells) and T lymphocytes (T cells)
- recognize and respond to particular
microbes and foreign molecules
(antigen)
How Specific Immunity
Arises
- B cells secrete proteins (antibodies)
to fight antigens
- T and B cells can distinguish among
antigens
- each antigen has a particular
molecular shape and stimulates certain
B cells to secrete antibodies that
interact with it
How Specific Immunity
Arises
- T and B cells recognize specific
antigens by plasma membrane-bound
antigen receptors
How Specific Immunity
Arises
Antigens interact with specific
lymphocytes, inducing immune
responses and immunological memory
- clonal selection: the cloning of
lymphocytes into plasma cells (shortlived) and memory cells (long-lived)
How Specific Immunity
Arises
How Specific Immunity
Arises
Primary immune response: the first time
the body is exposed to an antigen
- takes 10 to 17 days for effective
response to an antigen
Secondary immune response: when the
individual is exposed to the same
antigen at a later date
- takes 2 to 7 days
How Specific Immunity
Arises
How Specific Immunity
Arises
Lymphocytes originate from stem cells of
the bone marrow
- develop into T cells if the continue
their development in the Thymus
- develop into B cells if they finish
development in the bone marrow
How Specific Immunity
Arises
How Specific Immunity
Arises
The immune system exhibits the feature
of self-tolerance
- major histocompatibility complex
(MHC) are a series of glycoproteins
that mark the body as “self”
- MHC provides a biological fingerprint;
found in studying skin graft rejection
and acceptance
How Specific Immunity
Arises
There are two main types of T cells:
cytoxic T cells (TC) and helper T cells
(TH)
Cytoxic T cells have antigen receptors
that bind to protein fragments displayed
by class I MHC molecules
Helper T cells have receptors that bind
to peptides displayed by class II MHC
How Specific Immunity
Arises
Immune Responses
In response to antigens, the immune
system can mount a humoral response
or a cell-mediated response
Humoral immunity: involves B cell
activation and results from the
production of antibodies that circulate
in the blood plasma and lymph to attack
free antigens
Immune Responses
- B cells form Plasma cells
- plasma cells secrete antibodies for
an antigen
- B cells also give rise to B memory cells
- become activated during the
second infection
Immune Responses
Cell-mediated immunity: T cells are
active against viruses and bacteria that
have infected cells; also is crucial in the
body’s response against transplanted
tissues and cancerous cells
- activated T cells become TH or TC; TH
activate B cells that produce antibodies,
TC destroy infected body cells
Immune Responses