Important words and
concepts from Chapter 17, Black, 1999 (3/28/2003):
by Stephen T. Abedon (abedon.1@osu.edu)
for Micro 509
at the Ohio State University
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Course-external links are
in brackets Click [index] to access site index Click here to access
text’s website Vocabulary
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(1) Chapter title: Basic Principles of Specific Immunity and Immunization
(a)
[basic principles of specific
immunity and immunization (Google Search)] [index]
(a)
Immunology
is the study of specific immunity and the body's immune system that effects
(i.e., causes) this specific immunity
(b)
[immunology (Google Search)] [index]
(a)
Specific
immunity is that aspect of your body's defenses against pathogens (and other
foreign material) that acts against specific molecules, usually requiring that
your immune system "learn" the properties of specific molecules over
a number of days or weeks before mounting an effective response against the
foreign material
(b)
Typically
a specific immune response against one pathogen will be ineffective against a
different pathogen, sometimes even a closely related but still different
pathogen
(c)
Specific
immunity is that aspect of immunity that is primed when individuals are
vaccinated against, for example, pathogens or their toxins
(d)
Specific
immunity includes humoral immunity and cell-mediated immunity
(e)
A
number of body organs, tissues, and cell types are involved in effecting each
of these forms of specific immunity
(f)
We
can additionally describe specific immunity as being
(i)
Naturally acquired versus artificially acquired
(ii)
Actively
acquired versus passively acquired
(g)
[specific immunity (Google Search)] [index]
(a)
Another
way of defining specific immunity is that it is a means by
which a body defends itself against the presence of specific antigens
associated with, for example, pathogens
(b)
Antigens
are the protein or polysaccharide components of pathogens
(c)
The
reason that specific immunity is specific
to specific pathogens (and their molecules) is because these molecules
(antigens) are somewhat unique going from pathogen to pathogen (e.g., proteins
with different amino acid sequences and therefore different structures, or
polysaccharides made up of different sugars in different orders)
(d)
For
example, antibodies work by interacting with (binding to) specific
structures found on specific antigens
(e)
[antigen (Google Search)] [index]
(a)
Nonspecific
immunity includes those defenses against pathogens, etc., that are not specific
to each pathogen including such things as physical barriers, chemical barriers,
some cellular defenses, inflammation, fever, and molecular defenses
(b)
[nonspecific immunity
(Google Search)]
[nonspecific
host defenses and host systems (MicroDude)] [index]
(6) Innate immunity (genetic immunity, species immunity)
(a)
While
specific immunity must be learned (i.e., may be acquired),
innate immunity (a.k.a., genetic immunity) is present prior to the exposure to
a pathogen
(b)
This
is because innate immunity refers simply to the inability of many organisms
that have not evolved to be, for example, human pathogens, to cause disease in
(again, for example) humans because of the absence of mechanisms necessary to
be invasive in humans
(c)
Thus,
you are immune to the majority of pathogens associated with the majority of
host species simply because those pathogens are adapted to causing disease in a
different host setting (a.k.a., species
immunity)
(d)
[innate immunity, genetic immunity, species immunity (Google Search)] [index]
(a)
Acquired
immunity contrasts with innate immunity because it requires
previous exposure to a pathogen (or its product) before immunity is acquired by
the host
(b)
Acquired
(specific) immunity is the immunity that is responsible for subsequent
exposures to the same pathogens causing less or no disease (i.e., your becoming
"immune")
(c)
There
are two categories of means by which such immunity may be acquired, artificially and naturally
(d)
See Figure 17.1, The various
types of immunity
(e)
[acquired immunity (Google Search)] [index]
(8) Naturally acquired immunity (colostrum)
(a)
Naturally
acquired immunity is that immunity acquired upon exposure to a specific
pathogen particularly in the course of an infection/disease
(b)
Additionally,
naturally acquired immunity occurs when an infant obtains colostrum from mom
(c)
"Colostrum is the first fluid secreted
by the mammary glands after childbirth. Although deficient in many nutrients
found in milk, colostrum contains large quantities of antibodies that cross the
intestinal mucosa and enter the infant's blood."
(d)
The
infant is thus naturally immune against many or all of the diseases that the
mother is immune to especially as a consequence of the mother possessing
antibodies (a form of specific immunity) against the associated pathogens
(e)
See Figure 17.1, The various
types of immunity
(f)
[naturally acquired immunity,
colostrum (Google Search)] [index]
(9) Artificially acquired
immunity (antiserum,
antitoxin)
(a)
Specific immunity may also be acquired artificially
(b)
Artificially
acquired specific immunity basically constitutes the various means by which
humans enhance, via technology, the specific immunity of individuals
(c)
Artificially
acquired immunity specifically refers to vaccination (which
is an artificial exposure to a pathogen's antigens, i.e., without infection or,
at least, without disease) and to the transfusion of antibodies from one
individual into another (antiserum or antitoxin, etc.)
(d)
See Figure 17.1, The various
types of immunity
(e)
[artificially acquired immunity,
antiserum, antitoxin (Google Search)] [index]
(a)
Active
immunity occurs when an individual's own immune system is induced to produce a
specific immune response against an antigen/pathogen
(b)
Active
immunity can occur either upon infection or disease (naturally acquired active
immunity), or artificially upon vaccination (artificially acquired active
immunity); note that there is some ambiguity in the definitions I've used since
vaccines
can cause infections so the distinction between artificially and naturally acquired immunity is really one
between how the antigens were acquired, by natural versus by
artificial means
(c)
Active
immunity can last as long as the immune system cells, that mediate this
immunity, survive within an individual; this can be for weeks, months, or years
(d)
See Figure 17.1, The various
types of immunity
(e)
[active immunity (Google Search)] [index]
(a)
Passive
immunity results when antibodies are produced by one individual and
then acquired by another
(b)
The
acquisition of the antibodies in colostrum by an infant is an example of (naturally acquired) passive immunity; the
crossing of the placenta by maternal antibodies is another example of naturally
acquired passive immunity
(c)
Passive
immunity may also be artificially acquired,
particularly when antiserum or antibodies produced by one individual are
transfused into a second individual
(d)
In
all cases, passive immunity represents the passive acquisition of an immune
response that was actively acquired by another individual
(e)
However,
because passive immunity involves the transfusion of molecules rather than the
transfusion of immune system cells, passive immunity can last for at most
months since antibodies have a finite life span within the body
(f)
On
the other hand, passive immunity is functional immediately upon reception,
whereas active immunity (ironically) requires time (days, weeks) before a
functional immune response develops
(g)
See Figure 17.1, The various
types of immunity
(h)
[passive immunity (Google Search)] [index]
(a)
Synonymous
with antigen,
an immunogen/antigen is "a substance the body identifies as foreign and
toward which it mounts an immune response… Most antigens are large protein
molecules with complex structures and molecular weights greater than 10,000
[Daltons]. Some antigens are polysaccharides, and a few are glycoproteins
(carbohydrate and protein)… Proteins usually have greater antigenic
(immunogenic) strength because they have a more complex structure than
polysaccharides." That is, proteins possess many more potential epitopes
than do carbohydrates
(b)
"Antigens
are found on the surface of viruses and all cells, including bacteria, other
microorganisms, and human cells. The exact chemical structure of each of a
cell's antigens is determined by genetic information in its DNA. Bacteria can
have antigens on capsules, cell walls, and even flagella. Many microorganisms
have several different antigens somewhere on their surface. Determining how the
human body responds to these different antigenic determinants is important in
making effective vaccines. …antigens on the surfaces of red blood cells
determine blood types, and antigens on other cells determine whether a tissue
transplanted from another person will be rejected."
(c)
[immunogen and antigen
(Google Search)]
[index]
(13) Epitope (antigenic determinant)
(a)
Complex
antigens
such as proteins produce more robust immune responses because each structure/complexity
on an antigen can serve as the site of binding of a different immune system
molecule (e.g., an antibody)
(b)
Each
of these separate binding areas/structures is called an epitope (a.k.a.,
antigenic determinant)
(c)
Complex
antigens possess numerous epitopes and the binding of immune system molecules
(e.g., antibodies) to epitopes can have different effects depending
on the epitope
(d)
[epitope (Google Search)] [index]
(a)
Haptens
are small molecules that can serve as antigens (i.e.,
display immunologically recognized epitopes) upon binding to a larger molecule
(e.g., a protein)
(b)
Allergies
to penicillin occur because penicillin can serve as a hapten upon binding to
certain body proteins
(c)
[hapten (Google Search)] [index]
(a)
One
of the immune system molecules that bind to the epitopes on antigens is the
antibody
(b)
Antibodies
are secreted proteins that are found as soluble proteins in body fluids (for
more on antibodies, see immunoglobulin, below)
(c)
One
measures the quantity of antibodies in terms of antibody titers (e.g., active antibody per unit volume)
(d)
See Figure 17.2, A typical
antigen-antibody reaction
(e)
[antibody defenses, antibody titer (Google Search)] [index]
(16) Lymphocytes (white
blood cells)
(a)
Lymphocytes
are one category of white blood cells
(b)
Lymphocytes mediate specific immunity
(c)
We
can differentiate lymphocytes into a variety of types including, particularly,
the B lymphocytes (B cells) and the T lymphocytes (T
cells)
(d)
[lymphocytes, white blood cells (Google Search)]
[index]
(a)
B
lymphocytes are the producers of antibodies; that
is, they mediate humoral immunity
(b)
B
cells are not matured in the thymus
(c)
[B lymphocytes (Google Search)] [index]
(a)
T
cells mediate cell-mediated immunity
(b)
T
cells come in a variety of types which possess different antigens (proteins)
on their surfaces and which have different roles in the immune response
(c)
The
T in T cell stands for thymus and it
is in the thymus that T cells mature, especially in immature immune systems
(d)
["T lymphocytes" and
immunity -HIV -AIDS (Google Search)] [index]
(19) Clonal selection hypothesis (self, nonself, tolerance)
(a)
The
immune system possesses the ability to recognize antigens/epitopes
to which it has never been exposed (nonself)
(b)
In
addition, the immune system possesses the ability to not recognize (i.e., not bind to) antigens/epitopes associated with
normal body tissues (self)
(c)
The
means by which both of these mechanisms occur includes the selective
amplification of those immune system components that recognize foreign antigens
and the selective deletion of those immune system components that recognize
normal body tissues
(d)
Together
these mechanisms constitute the clonal selection hypothesis
(e)
"According
to this hypothesis, embryos contain many different lymphocytes, each
genetically programmed to recognize a particular antigen and make antibodies to
destroy it. If a lymphocyte encounters and recognizes that antigen after
development is complete, it divides repeatedly to produce a clone, a group of
identical progeny cells that make the same antibody. If, during embryonic
development, it encounters its programmed antigen as part of a normal host
substance (self), the lymphocyte is somehow destroyed or inactivated. This
mechanism removes lymphocytes that can destroy host tissues and thereby creates
tolerance for self. It also selects
for survival [of] lymphocytes that will protect the host from foreign
antigens."
(f)
See Figure 17.5, Clonal
selection hypothesis
(g)
See Figure 17.6, Clonal
deletion
(h)
[clonal selection hypothesis,
tolerance and clonal selection
hypothesis, self and clonal selection
hypothesis, non-self and clonal selection
hypothesis, nonself and clonal selection
hypothesis (Google Search)]
[B cell maturation, activation of B cell with
thymus-independent antigen, B cell selection
(shockwave movies of complex molecular process) (Immunology Bio307)]
[index]
(a)
The
hallmark of specific immunity is the specificity of the
immune response
(b)
This
means that an immune response to specific epitopes will not
be effective against a pathogen lacking these epitopes, even if the second
pathogen is otherwise closely related to the first
(c)
Specificity
is not necessarily perfect thus allowing, using the above example, partial
immunity against the second pathogen because the second pathogen shares some, but
not all epitopes with the first pathogen
(d)
[specificity and immunity
(Google Search)]
[index]
(a)
Actively
acquired specific immunity possesses memory
(b)
This
is another way of saying that an immune response may be primed by exposure to
an antigen,
and thereafter with subsequent exposure to the same antigen the immune response
against that antigen occurs much more rapidly
(c)
This
memory is a function of the circulation of the lymphocytes which
either mediate the specific immune response or can give rise to cells (i.e., by
dividing) that differentiate into immune-response-mediating cells
(d)
Subsequent
exposure to an antigen, in sufficient quantity, will also serve to strengthen
subsequent immune responses
(e)
[memory and immunity
(Google Search)]
[index]
(22) Humoral immunity [memory cells, plasma
cells]
(a)
That
aspect of specific immunity that is mediated by antibodies
is termed humoral immunity
(b)
Humoral
immunity is particularly effective against toxins (exotoxins), whole bacteria,
and free viruses (i.e., viruses not currently infecting cells)
(c)
"Humoral
immunity depends first on the ability of B lymphocytes to recognize specific
antigens and second on their ability to initiate responses that protect the
body against foreign agents. The most common response is the production of
antibodies that will inactivate an antigen and lead to destruction of
infectious organisms."
(d)
B cells,
which mediate humoral immunity, each produce only a single kind of antibody
(i.e., one structure with the ability to bind to only a single type/structure
of epitope)
(e)
These
antibodies are displayed on the surface of B cells
(f)
The
binding of an antigen to one of these surface B cells induces those cells
either to start producing antibody or to differentiate into cells that produce
antibody
(g)
These
antigens may be soluble, found on the surface of pathogens, or displayed by
other immune system cells such as macrophages
(h)
Plasma cells are those B cells that can
immediately produce (and secrete) antibody molecules
(i)
Memory cells are those more
long-term-stable B cells that can differentiate into plasma cells
(j)
[humoral immunity, memory cells, "plasma cells" and
humoral (Google Search)]
[index]
(a)
Another
name for antibody is immunoglobulin
(b)
See Figure 17.7, Antibody
structure
(c) Note that antibodies come in a variety of classes (i.e., IgG, IgM, IgA, IgE, and IgD) possessing variations on the basic antibody structure<