Download Chapter 43 Student Guided Notes

Chapter 43  The Immune System
Student Guided Notes
Overview: Recognition and Response

An animal must defend itself against pathogens, _________________________________________.

______________________________________ help animals to avoid or limit many infections.

Innate immunity (also known as NON-SPECIFIC IMMUNITY) is common to all animals. Such
defenses are active immediately upon infection and are the same whether or not the pathogen has been
encountered before. These defenses do not discriminate between one infectious agent and another.
o External barriers (non-specific), formed by the skin or shell.
o Chemical secretions that trap or kill pathogens.
o Macrophages and other phagocytic cells that ingest and destroy pathogens.

An animal’s immune system must detect foreign particles and tissues that invade the body,
distinguishing ________________ from _______________________________.

Adaptive immunity (also known as SPECIFIC IMMUNITY) is found only in vertebrates. These
defenses respond in specific ways to particular microorganisms.
o Adaptive immune responses are activated after innate immune defenses and develop more slowly.
o These adaptive defenses are enhanced by previous exposure to the infecting pathogen.
Concept 43.1 In innate immunity, recognition and response rely on traits common to groups of
pathogens.
The skin and mucous membrane provide first-line barriers to infection.

In mammals, epithelial tissues block the entry of harmful viruses and bacteria.
o Mucous membranes produce mucus that _____________________________________________
_______________________________________________________________________________.
o In the trachea, __________________________________________ cells sweep out mucus with its
trapped pathogens.
o _____________________________________ in tears, saliva, mucous secretions, and tears kill
bacteria that enter the upper respiratory tract or the openings around the _________________.
o _________________________ destroys most pathogens before they can enter the intestinal tract.
o Secretions from sebaceous and sweat glands give the skin an acidic pH (pH of _____ - ______) to
prevent colonization by many pathogens.
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Phagocytic cells function early in infection.

The internal non-specific defense depends on phagocytosis and uses several types of cells:

Neutrophils

Damaged cells release signals that attract neutrophils; they then attack and
_____________________________________________________


Self-destruct; lifespan = few days
Monocytes

Circulate in blood then migrate into tissue where they form
__________________________________ (“big eaters”); very large

Some __________________________________________________________
and some stay in certain tissues; phagocytic


Eosinophils

Defend against larger parasites (ex. Blood flukes)

Position against invader and secrete _________________________________
Natural Killer (NK) cells

Destroy virus-infected body cells (don’t attack the microorganism directly)

Circulate through the body and _______________________________________
_________________________________________________________________
_________________________________________________________________
A variety of peptides and proteins attack pathogens.

Antimicrobial Proteins are used in nonspecific defense.

____________________________________ provide innate defenses by interfering with viral infection.
o These proteins are secreted by _________________________________________________ and
induce uninfected neighboring cells to produce substances that inhibit _______________________.
o The interferons limit the ___________________ spread of viruses, helping to control viral infection.

The complement system consists of roughly 30 proteins in blood plasma that circulate _____________
___________________________________________________________________________________.
o Activation results in a cascade of biochemical reactions that lead to __________________________
_____________________________________________________.
o The complement system functions in _________________________________ as well as in
____________________________________________________.
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Damage to tissue triggers an inflammatory response.

Damage to tissue by a physical injury or the entry of pathogens leads to the release of chemical signals
that trigger a localized inflammatory response.
o When injured, ____________________________ (part of connective tissue) release
___________________, which triggers both dilation and increased permeability of nearby capillaries.
o Histamine 

Main effect = dilates blood vessels

Can cause runny nose/eyes (allergies!)

Someone can take anti-histamines to reduce the effects
o Cytokines (signaling molecules) increase ______________________________________ and cause
the characteristic redness and heat of inflammation.
o Blood-engorged capillaries leak fluid into neighboring tissue, causing edema (swelling.)
o The end result is an accumulation of pus, a ____________________________________________
____________________________________________________________________.
o The inflammatory response is initiated by chemical signals (both from microorganism itself OR
released from the body); ex. histamine

A systemic response to infection is ________________, which may occur when substances released by
activated macrophages set the body’s thermostat at a higher temperature.
o One hypothesis is that moderate fever enhances _________________________________ and hastens
___________________________________.
Concept 43.2 In adaptive (SPECIFIC) immunity, receptors provide pathogen-specific recognition.
Vertebrates have adaptive immunity in addition to innate immunity.

Lymphocytes provide the specificity and diversity of the vertebrate immune system.

The vertebrate body is populated by two main types of lymphocytes: B lymphocytes (B cells) and T
lymphocytes (T cells).
o T lymphocytes (T cells)  originate from stem cells in the ____________________________ and
migrate to the ________________________ (gland above the heart) mature into T cells
o B lymphocytes (B cells)  mature in the ________________________________ develop as B cells
o Both types of lymphocytes are critical for adaptive immune defense.
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Lymphocytes recognize specific antigens. (AN OVERVIEW)

Any foreign molecule that is specifically recognized by lymphocytes and elicits a response from them is
called an ________________________________. (this stands for ANTIbody GENerating foreign
macromolecule) Antigens cause antibodies to be made!

A lymphocyte actually recognizes and binds to a small portion of an antigen called an
__________________ or antigenic determinant.
o Because lymphocytes recognize and respond to particular pathogens and foreign molecules, they are
said to display _________________________ for a particular ____________________ on an antigen.

Each B cell receptor for an antigen is a Y-shaped molecule consisting of four polypeptide chains:
____________________________________________ and ___________________________________.
o At the two tips of the Y-shaped molecules are the light- and heavy-chain ______________________
___________________________ whose amino acid sequences vary from one B cell to another.
o The remainder of the molecule is made up of _________________________________________,
which do not vary from cell to cell.

This protein is called an antibody, or ____________________________________.

T cell and B cell antigen receptors function in fundamentally different ways.
o While the antigen receptors of B cells bind to epitopes of ___________________ antigens
circulating in body fluids, those of T cells bind only to fragments of antigens that are
___________________, or ________________________, on the surface of _____________ cells.
o The host protein that _____________________________________________________________
______________________________ is called an MHC (major histocompatibility) molecule.

Movement of the MHC molecule and bound antigen fragment to the cell surface results in antigen
presentation, the ___________________________________________________________________
__________________________________________________________________________________.
o MHC  determines “self” from “non-self”; involved in tissue rejection (transplants); is a family of
genes that encodes the glycoproteins in cell membranes

_______________________________ and ________________________ arise as a lymphocyte matures.
o Proliferation of cells and the formation of ______________________________________________
occur later, after a mature lymphocyte _________________________________________________.
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How does adaptive immunity distinguish self from nonself?

Since the body normally _______________________________________________________________
________________________________________________________________________________, the
immune system is said to exhibit self-tolerance.
o Lymphocytes (when activated by a microorganism binding to it) form 2 clones:
1. Some cells from the clone become effector cells, which act against _______________________
_____________________________________________________________________________.
o Effector forms of B cells = plasma cells  which __________________________________
o Effector forms of T cells = ___________________________ and ______________________
2. The remaining cells in the clone become _________________________________, long-lived
cells that produce effector cells if the same antigen is encountered later in the animal’s life.
o
The proliferation of an activated lymphocyte into a clone of cells in response to binding to an antigen
is called ______________________________________.

____________________________________________ provides long-term protection from a prior
infection or vaccination.

The production of effector cells from a clone of lymphocytes during the first exposure to an antigen is
the basis for the ______________________________________________, which peaks ___________
_________________________________________________________________.
o During this time, selected B cells and T cells __________________________________________
___________________________________________.

If an individual is exposed again to the same antigen, the response is ___________________________
_________________________________________________________________________, of greater
magnitude, and __________________________________________.
o This is the ____________________________________________________.
Concept 43.3 Adaptive immunity defends against infection of body fluids and body cells.

The immune system can mount two types of immune responses to antigens: humoral and cell-mediated.
o Humoral Immunity  B cells activated; defend against
free (in the ____________________________________)
bacteria, toxins, and viruses present in body fluids; B cells
Humoral Immunity  B cells;
secretion of antibodies by plasma
cells; extracellular pathogens
Cell Mediated Immunity  T
cells; attack on infected cells
secrete antibodies
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o Cell- Mediated Immunity  T cells used; active against viruses and bacteria within infected body
cells; destroys ____________________________________________________
o Both responses include a _______________________________________________ and a ________
_____________________________________________ enabled by _____________________ cells.
Helper T lymphocytes function in both humoral and cell-mediated immunity.

Helper T cell (a type of T cell)  triggers ________________________________________________
___________________________________________________________.
o Signals from helper T cells initiate _____________________________________________
(humoral) that neutralize pathogens and activate T cells (cell-mediated) that ___________________
________________________________________________.

Two requirements must be met for a helper T cell to activate adaptive immune responses.
o First, a foreign molecule must be present that can bind specifically to the ____________________
_______________________________________________.
o Second, this antigen must be _______________________________________________________
___________________________________________________________.
o Antigen-presenting cells have both class I and class II MHC molecules.
SEE POWERPOINT AND ALSO Figures 43.16 p. 958 and 43.17 p. 959
In the cell-mediated immune response, cytotoxic T cells are the effector cells.

Class II MHC 
recognized by TH
(helper T cells)
Class I MHC 
recognized by TC
(cytotoxic T
cells)
To become active, cytotoxic T cells require signaling molecules from
___________________________________________________ as well as
interaction with a cell that presents an antigen.
o Once activated, cytotoxic T cells can eliminate cells that are infected by viruses or other intracellular
pathogens.
o Cytotoxic T cells attack intracellular pathogens and cancer cells

Fragments of foreign proteins produced in infected host cells associate with ______________________
__________________________ and are __________________________________________________,
where they can be recognized by ________________________________________.
SEE POWERPOINT AND ALSO Figures 43.18 p. 960 and 43.20 p. 962
The secretion of antibodies by clonally selected B cells is the hallmark of the humoral immune response.
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
Activation of the humoral immune response typically involves B cells and helper T cells, as well as
proteins on the surface of pathogens.
o Stimulated by both an antigen and cytokines, the B cell proliferates and differentiates into _______
__________________________________ and __________________________________________
_____________________________________________________.

An exposure to a single antigen normally activates a variety of B cells, with different plasma cells
producing antibodies directed against different epitopes on the common antigen.

Antibodies do not ______________________________________, but by binding to antigens they mark
pathogens in various ways for inactivation or destruction.
1. Neutralization  binding blocks the activity of the antigen
2. Opsonization  bound antibodies enhance attachment of macrophages (yields phagocytosis)
3. Agglutination  clumping of bacteria or viruses; occurs b/c each antibody has at least two
antigen binding sites; these large complexes are phagocytosed by macrophages
4. Complement Fixation  activation of the complement system (serum proteins are activated);
yields lysis of many types of viruses and pathogenic cells

When a particular pathogen infects the body, clones of memory cells form, providing ___________
____________________________________. This depends on a persons own immune system (ex.
Getting over chicken pox) and can be acquired naturally or by immunization/vaccination.

In contrast, ________________________________________________ results when the antibodies in
the blood of a pregnant female cross the placenta to her fetus.
o Passive immunity is when antibodies are transferred from one person to another (ex. Antibodies of a
pregnant woman cross the placenta to the fetus; breastmilk) and last only as long as those antibodies
last (weeks to months)

Both active immunity and passive immunity can be induced _____________________________.

Active immunity can develop from _____________________________________________________
__________________________________________________ through immunization.
o The first documented immunization or vaccination (Edward Jenner 1796) was the use of
_____________________________________ to induce adaptive immunity against the closely
related _________________________________________.
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Transplanted cells may be recognized as foreign and attacked by immune defenses.

Like pathogens, cells from another person can be recognized as foreign and therefore be attacked by
immune defenses.

To avoid a blood transfusion being recognized as foreign by the recipient’s immune system, ABO blood
groups of the donor and recipient must be taken into account.

Red blood cells are designated as type A if they have the ____________________________________
____________________________________________________________.
o The _________________________________________________ is found on type B red blood cells;
both A and B carbohydrates are found on _______________________ red blood cells; and
_________________________________________ is found on type O red blood cells.
o People with type A blood make anti-B antibodies.
o People with type B blood make anti-A antibodies.
o People with type AP blood make neither, and people with O make both types

If a person with type A blood receives a transfusion of type B blood, that person’s anti-B antibodies
cause an immediate and devastating transfusion reaction. When exposed to the “wrong” type of blood,
the antibodies will bind to the “new” blood and clump around it.

The Rh factor is a protein on the outside of a blood cell. This can be a problem if the mom is Rh
negative and the fetus is Rh positive if small amounts of blood cross the placenta. Rh antibodies can
cross the placenta, but ABO ones cannot.
Concept 43.4 Disruptions in immune system function can elicit or exacerbate disease.
Exaggerated immune responses can cause disease.

Allergies are ______________________________________________________________________ to
certain environmental antigens, called allergens.

Histamines are released when these antigens bind; histamine causes dilation and increased permeability
of the small blood vessels; this causes allergy symptoms: sneezing, runny nose, teary eyes, and smooth
muscle contractions that can result in breathing difficulty.

with epinephrine, which counteract
o Antihistamines diminish allergy symptoms by blocking receptors for histamine.
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
Sometimes, an acute allergic response can result in ________________________________________, a
whole-body, life-threatening reaction to injected or ingested allergens.

Anaphylactic shock results when widespread release of mast cell contents triggers abrupt dilation of
peripheral blood vessels, causing a precipitous drop in blood pressure and constriction of branchioles.
o Some hypersensitive individuals carry syringes s this allergic response.
Self-directed immune responses can cause disease.

Sometimes the immune system is active against certain molecules of the body, causing an autoimmune
disease. Examples include: ____________________, _______________________________________,
___________________________________________, _____________________________________

Autoimmune Diseases occur when your body loses tolerance of self and turns against your own cells.

Gender, genetics, and environment influence susceptibility to autoimmune disease.
Diminished immune responses can cause disease.
 In immunodeficiency diseases, _________________________________________________________
______________________________________________________________________.
HIV attacks the immune system.
 The human immunodeficiency virus (HIV), the pathogen that causes AIDS, escapes and attacks the
adaptive immune response.
 HIV gains entry into cells by making use of proteins that participate in normal immune responses.
 One reason HIV persists is antigenic variation.
 The continued presence of HIV is also helped by ____________________________.
HIV infection cannot yet be cured, although certain drugs slow HIV reproduction and the progression to AIDS.
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