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Acquired Immunity: Humoral Response
• Distinction of Humoral versus Cell-Mediated Acquired Immunity
• Antigens and Antigenic Determinants: Non-self and MHC proteins
• Cell Types of the Humoral Response and How they Develop
• B and T cell receptors and immunglobulins (antibodies)
• Antibody Structure and Classes
• Activation of B cells and Clonal Selection
• Immunity and Secondary Response Time
• Antibody Actions
• Passive and Active Immunity
• Monoclonal Antibodies
• Cell-Mediated Immune System: T cells, Grafting
Body Defenses: Innate and Acquired
Defense Systems of the Body
 Non-specific defense system (Innate Immune System)
• Mechanisms protect against a variety of invaders
• Responds immediately to protect body from foreign materials
 Specific defense system (Acquired Immune System: Humoral and Cell-Mediated)
• Specific defense is required for each type of invader
• Also known generically as just “the immune system”
(Innate immunity)
Nonspecific (Innate) Body Defenses
Mechanical, Chemical, and Competitive Barriers
, urine, blood, saliva
Skin produces acidic sebum
to limit bacterial growth and
sebum fatty acids are
fungistatic
Saliva and tears destroy bacteria
because they contain lysozyme.
Nitric oxide (NO) released by
macrophages inhibit ATP production
Iron-binding proteins in blood
block microbial reproduction
Inflammation
Figure 16.9c, d
The Complement System
 Serum proteins
activated in a
cascade.
 Results:
• Opsonization
• Chemotaxis
• Transmembrane
channel formation in
cells tagged by
antibodies (causing
cytolysis)
• Triggers inflammation
Figure 16.10
Body Defenses: Innate and Acquired
Defense Systems of the Body
 Non-specific defense system (Innate Immune System)
• Mechanisms protect against a variety of invaders
• Responds immediately to protect body from foreign materials
 Specific defense system (Acquired Immune System: Humoral and Cell-Mediated)
• Specific defense is required for each type of invader
• Also known generically as just “the immune system”
(Innate immunity)
Acquired Immune System – Third Line of Defense
The Acquired Immune System is:
 Antigen specific – recognizes and acts against
particular foreign substances
 Systemic – not restricted to the initial infection site
 Has memory – recognizes and mounts a stronger
attack on previously encountered pathogens
Types of Acquired Immunity
1. Humoral Immunity
• Antibody-mediated
immunity in blood and
lymph
• Cells produce chemicals for
defense
2. Cellular immunity of the CellMediated Immune System
• Cell-mediated immunity
• Cells target virally infected
cells
Antigens (Nonself)
 Antigen: Any substance capable of
exciting the immune system and
provoking an immune response
Antigens
 Examples of common antigens
• Foreign proteins
• Nucleic acids
• Large carbohydrates
• Some lipids
• Pollen grains
• Microorganisms
 Antigenic determinants:
substances (like glycoproteins) on
the surface of antigens to which
the immune system actually
responds
Antigen
Receptor in the immune
system that "fits" the
antigenic determinant
Self-Antigens
 Human cells have many
surface proteins called
major histocompatability
complexes (MHC).
 All body cells have MHC
Class I proteins.
 Our immune cells do not
attack our own proteins
 Our cells in another
person’s body can trigger
an immune response
because they are foreign
• Restricts donors for
transplants
Allergies
 Many small molecules (called
haptens or incomplete
antigens) are not antigenic, but
link up with our own proteins
 The immune system may
recognize and respond to a
carrier-hapten combination
 This immune response can be
harmful rather than protective
because it can attack small
molecules mounted on our own
cells or small molecules
normally found in the
environment that bind to
carriers  allergy or
autoimmunity
Humoral (Innate) Immune Response
• Distinction of Humoral/Innate versus Cell-Mediate Response
• Antigens and Antigenic Determinants: Non-self and MHC proteins
• Cell Types of the Humoral Response and How they Develop
• B and T cell receptors and immunglobulines (antibodies)
• Antibody Structure and Classes
• Activation of B cells and Clonal Selection
• Immunity and Secondary Response Time
• Antibody Actions
• Passive and Active Immunity
• Monoclonal Antibodies
Cells of the Immune System
 Lymphocytes
• Originate from
hemocytoblasts in the red
bone marrow
• B lymphocytes become
immunocompetent in the
bone marrow
• T lymphocytes become
immunocompetent in the
thymus
 Macrophages (certain mature
granulocytes)
• Arise from monocytes
• Become widely distributed
in lymphoid organs
Development of Lymphocytes
T cell maturation
and "education"
B Cell Receptors, T Cell Receptors, and Immunoglobulins
T cell
B cell
Receptors on T Cells
Receptors on B cells
Constant
regions
Variable
(binding)
regions
Secreted (Exported)
Immunoglobulin or Antibody
(Same V and C Regions as in B cell
receptors)
Humoral (Innate) Immune Response
• Distinction of Humoral/Innate versus Cell-Mediate Response
• Antigens and Antigenic Determinants: Non-self and MHC proteins
• Cell Types of the Humoral Response and How they Develop
• B and T cell receptors and immunglobulines (antibodies)
• Antibody Structure and Classes
• Activation of B cells and Clonal Selection
• Immunity and Secondary Response Time
• Antibody Actions
• Passive and Active Immunity
• Monoclonal Antibodies
Immunoglobulins and Receptors Bind To Antigens
Agglutination of antigens
Different Classes of Antibodies
Humoral (Innate) Immune Response
• Distinction of Humoral/Innate versus Cell-Mediate Response
• Antigens and Antigenic Determinants: Non-self and MHC proteins
• Cell Types of the Humoral Response and How they Develop
• B and T cell receptors and immunglobulines (antibodies)
• Antibody Structure and Classes
• Activation of B cells and Clonal Selection
• Immunity and Secondary Response Time
• Antibody Actions
• Passive and Active Immunity
• Monoclonal Antibodies
B Cell Activation and Clonal Selection
Humoral
immunity
movie
Secondary Response (Immunity)
Figure 12.13
Results of Antibody Binding to Antigen
• Agglutination (coralling of the invader)
• Precipitation (removal of soluble antigens from blood and lymph)
• Neutralization (blocking antigen's activity and binding)
• Opsonization (faciliating macrophage phagocytosis)
• Tagging, complement fixation, and transmembrane channel
formation (lysis of pathogen)
Agglutination
Antibody
Function
movie
Precipitation
(soluble antigens)
Transmembrane
channel formation
and lysis
Humoral (Innate) Immune Response
• Distinction of Humoral/Innate versus Cell-Mediate Response
• Antigens and Antigenic Determinants: Non-self and MHC proteins
• Cell Types of the Humoral Response and How they Develop
• B and T cell receptors and immunglobulines (antibodies)
• Antibody Structure and Classes
• Activation of B cells and Clonal Selection
• Immunity and Secondary Response Time
• Antibody Actions
• Passive and Active Immunity
• Monoclonal Antibodies
Active vs Passive Immunity
 Active Immunity
• Your B cells encounter antigens
and produce antibodies
• Active immunity can be
naturally or artificially acquired
(e.g via vaccination)
 Passive Immunity
• Antibodies are obtained from
someone else
o
Conferred naturally from a
mother to her fetus
o
Conferred artificially from
immune serum or gamma
globulin
• Immunological memory does not
occur
• Protection provided by
“borrowed antibodies”
Monoclonal Antibodies
 Antibodies prepared for
clinical testing or diagnostic
services
 Produced from descendents
of a single cell line
 Examples of uses for
monoclonal antibodies
• Diagnosis of pregnancy
• Treatment after exposure
to hepatitis and rabies
• HIV/AIDS detection in
ELISA Assays
Humoral (Innate) Immune Response
• Distinction of Humoral/Innate versus Cell-Mediate Response
• Antigens and Antigenic Determinants: Non-self and MHC proteins
• Cell Types of the Humoral Response and How they Develop
• B and T cell receptors and immunglobulines (antibodies)
• Antibody Structure and Classes
• Activation of B cells and Clonal Selection
• Immunity and Secondary Response Time
• Antibody Actions
• Passive and Active Immunity
• Monoclonal Antibodies
Cell Mediated Immune Response
 Players in the Cell Mediated Response
 Activation of Cytotoxic T and B cells via TH cells
 Other T cells and their function
 Tissue grafting
Cellular (Cell-Mediated) Immune Response
1. Antigens must be presented by macrophages to an
immunocompetent T cell (antigen presentation)
2. T cells must recognize non-self antigen and
self MHC proteins (double recognition)
3. After antigen binding, clones form as with B
cells, but different classes of cells are
produced
Activation of T and B Cells Through TH cells
MHC "self"
identifying
protein
Types of T Cells
 Cytotoxic T (Tc) cells
• Specialize in killing infected cells
• Insert a toxic chemical (perforin)
 Helper T (TH) cells
Cytotoxic t cells animation
• Recruit other cells to fight the invaders
• Interact directly with B cells
 Suppressor T cells
Helper t cells animation
• Release chemicals to suppress the activity of T and B cells
• Stop the immune response to prevent uncontrolled activity
 A few members of each clone are memory cells
Summary of B Cell Activation
 B cells can be activated directly by antigen or from a TH cell
activated by an antigen-presenting macrophage
Summary of the Immune Response
Organ Transplants and Rejection
 Major types of grafts
• Autografts – tissue transplanted from
one site to another on the same person
• Isografts – tissue grafts from
an identical person (identical
twin)
• Allografts – tissue taken from
an unrelated person (sometimes
successful)
• Xenografts – tissue taken from
a different animal species
(rarely successful)
Hey buddy, my patch of
skin is damaged! Can I
have your autograft?