Transcript Active Immunity

ADAPTIVE IMMUNITY
Paula Ruedebusch, ARNP, DNP
ADAPTIVE IMMUNITY

Purposes:
Destruction of infectious microorganisms that are
resistant to inflammation
 Long-term highly effective protection against future
exposure to the same microorganism

Inducible
 Specific
 End products

Immunoglobulins
 Lymphocytes (T cells, B cells)

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ADAPTIVE IMMUNITY (CONT’D)

Components:

Humoral—immunoglobulins (antibodies)


Bind to antigens on bacteria and viruses
Cellular—T cells

Subpopulations (effector T cells)
 Kill target directly
 Stimulate other leukocytes
Both produce memory cells
 Interact

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ADAPTIVE IMMUNITY (CONT’D)

Active immunity
Exposure to antigen
 Immunization


Passive immunity
Preformed antibodies or T cells are administered
 Maternal-fetal transmission
 Temporary

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Active Immunity
(vaccination)
Passive Immunity
(antitoxins)
Develops due to infection or
immunization
Preformed antibodies are
injected
There is a short lag period.
Does not give immediate
protection
No lag period. Gives immediate
protection.
Effective immunity – it is longlasting.
Immunity is short-lived.
Antibodies are quickly
eliminated.
Repeated doses give more and
more protection (booster
response)
Repeated doses give less and
less protection.
Not useful in a person with
immunodeficiency
Useful to protect
immunodeficient people
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ADAPTIVE IMMUNITY (CONT’D)

Antigens
Bind with antibodies, receptors on T and B cells
 Not necessarily immunogens


Immunogens
Induce production of antibodies, T and B cells
 Depends on foreignness, molecular size, quantity
 All are antigens

Entry route (intravenous, intradermal, oral)
stimulates different lymphoid tissue
 Genetics
 Other factors (nutrition, concurrent disease, drugs)

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VACCINE ROUTES
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ANTIGENS
Antigenic determinant (epitope) = ON antigen
 Antigenic binding site (paratope) = ON antibody
 Self-antigen
 Molecular size



Haptens
Allergens
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HUMORAL IMMUNITY

Immunoglobulins (antibodies)
Produced by plasma cells
 Types:

IgG
 IgA
 IgM
 IgD
 IgE

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ANTIBODIES
Also called immunoglobulins
 Produced by plasma cells
 Classes of antibody


IgG, IgA, IgM, IgE, and IgD

Characterized by antigenic, structural, and functional
differences
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ANTIBODIES (CONT’D)
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ANTIBODY STRUCTURE

Antigen-binding fragment (Fab)


Crystalline fragment (Fc)


Recognition sites (receptors) for antigenic determinants
Responsible for biologic function
Polypeptide chains (4)

Light chains (2) and heavy chains (2)
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HUMORAL IMMUNITY

Antigen-Antibody Binding:
Antigenic determinant (epitope) = area of molecule that
is recognized by the antibody
 Antigen-binding site (paratope) = the matching portion
on the antibody

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ANTIBODY FUNCTIONS

Antibody functions:

Direct
Neutralization
 Agglutination
 Precipitation


Indirect
Inflammation
 Phagocytosis
 Complement


Degree of antibody protection is assessed by an
antibody titer
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DIRECT AND INDIRECT FUNCTIONS OF
ANTIBODIES
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TITER EXAMPLE
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IMMUNOLOGIC MECHANISMS OF INFLAMMATION
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IMMUNOGLOBULIN A (IGA) (CONT’D)

IgAs found in body secretions are dimers anchored by
a J chain and a “secretory” piece

Secretory piece may function to protect IgAs against
enzyme degradation
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IMMUNOGLOBULIN D (IGD)
Limited information on IgD function
 Low concentration in the blood
 Located primarily on the surface of developing B
lymphocytes
 Function as one type of B cell antigen receptor

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IMMUNOGLOBULIN E (IGE)
Least concentrated of the immunoglobulin classes
in the circulation
 Mediator of many common allergic responses
 Defender against parasites

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IGE FUNCTION

Provides protection from large parasites


Initiates an inflammatory reaction to attract eosinophils
When produced against innocuous environmental
antigens, they are a common cause of allergies
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IGE FUNCTION (CONT’D)
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IMMUNOGLOBULIN G (IGG)
Most abundant class (80%-85%)
 Accounts for most of the protective activity against
infections
 Transported across the placenta
 Four classes:

IgG1
 IgG2
 IgG3
 IgG4
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IMMUNOGLOBULIN M (IGM)
Largest of the immunoglobulins
 First antibody produced during the primary
response to an antigen
 Synthesized during fetal life
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SECRETORY (MUCOSAL) IMMUNE SYSTEM
Lymphoid tissues that protect the external
surfaces of the body
 Antibodies present in tears, sweat, saliva, mucus,
and breast milk
 IgA is the dominant immunoglobulin


Small numbers of IgG and IgM are present
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SECRETORY (MUCOSAL) IMMUNE SYSTEM
(CONT’D)
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CELLULAR IMMUNITY

T lymphocytes:
T Cytotoxic (Tc) cells
 T Helper (Th) cells
 Memory cells

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ADAPTIVE IMMUNITY

Clonal diversity
Production of T and B lymphocytes
 Antigen recognition
 Lymphocyte specificity


Clonal selection
Antigen processing and presentation
 Complex cellular interactions
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GENERATION OF CLONAL DIVERSITY
All necessary receptor specificities are produced
 Takes place in the primary (central) lymphoid
organs (thymus, bone marrow)
 Results in immature but immunocompetent T and
B cells
 Primarily occurs in the fetus
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CLONAL DIVERSITY

B Cell Development:
Production, proliferation, differentiation in bone marrow
 Travel to lymphoid tissue and reside there as
immunocompetent cells
 Each cell responds to only one specific antigen


T Cell Development:
The thymus is the central lymphoid organ of T cell
development
 Development of antigen-specific T cell receptors
(TCRs)
 Leave thymus, travel to and reside in lymphoid tissue
as mature immunocompetent cells
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CLONAL SELECTION: ANTIGEN PROCESSING
AND PRESENTATION
Initiated when T and B cells interact with an
antigen
 Must first be processed and then presented by
antigen-processing (antigen-presenting) cells
(APCs)
 Results:

Differentiation of B cells into active antibody-producing
cells (plasma cells)
 Differentiation of T cells into effector cells, such as Tcytotoxic cells
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CLONAL SELECTION: ANTIGEN PROCESSING AND
PRESENTATION (CONT’D)

For processing and presentation to occur, the
antigen must be of the appropriate type, the
lymphocytes must be prepared to recognize the
presented antigen, and the antigen must be
presented appropriately
https://www.youtube.com/watch?v=bfL6ORCVuF4
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ANTIGEN PROCESSING AND PRESENTATION
(CONT’D)
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ANTIGEN PRESENTATION

Major histocompatibility complex (MHC)
Glycoproteins on the surface of all human cells (except RBCs)
 Also referred to as human leukocyte antigens (HLAs)
 Dendritic cells – antigen presenting leukocyte found in mucosa
and lymphoid tissues that initiate a primary immune response.
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PRIMARY AND SECONDARY RESPONSES

Primary response
Initial exposure
 Latent period or lag phase


B cell differentiation is occurring
After 5 to 7 days, an IgM antibody for a specific
antigen is detected
 An IgG response equal or slightly less follows the IgM
response
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PRIMARY AND SECONDARY RESPONSES
(CONT’D)

Secondary response
More rapid
 Larger amounts of antibody are produced
 Rapidity is caused by the presence of memory cells
that do not have to differentiate
 IgM is produced in similar quantities to the primary
response, but IgG is produced in considerably greater
numbers
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SUPERANTIGENS (SAGS)
Activates a large population of T-lymphocytes
regardless of antigen specificity
 SAGs induce an excessive production of cytokines


Causes fever, low blood pressure, and potentially
shock
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PEDIATRIC IMMUNITY
Fetus has sufficient IgM but deficient IgG, IgA
responses
 Maternal antibodies provide protection within the
fetal circulation and during the first months of life
 Immunologically immature when born with
deficiencies in antibody production, phagocytic
activity, and complement activity
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FETAL AND NEONATAL IMMUNITY
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AGING AND IMMUNE FUNCTION

Decreased T cell activity

Thymic size is 15% of its maximum size
Thymic hormone production drops, as does the
organ's ability to mediate T cell differentiation
 Decreased antibody response to antigens
 Increase in circulating antigen-antibody complexes
 Increase in circulating autoantibodies
 Decrease in circulating memory B cells
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TEST YOURSELF!
Which of the following terms describes the type of
immunity that occurs when preformed antibodies
transfer from donor to recipient?
A.
B.
C.
D.
Active
Passive
Cellular
Memory
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CLINICAL APPLICATION #1

Mr. Jones became infected with the HIV virus on
Friday night. The following Monday, he donated a
unit of blood. The blood will be screened for the
presence of HIV using an antibody test. Will his
blood test be positive for the virus? Why?
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CLINICAL APPLICATION #2

Judi Smith, age 5, is about to receive a vaccine
during her regular checkup. Her mother asks you
why she needs this “shot.”
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