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 AcquiredDefense 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
(Innate immunity)
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”
Nonspecific (Innate) Body DefensesMechanical, Chemical, and Competitive Barriers
Saliva and tears destroy bacteria because they contain lysozyme.
Skin produces acidic sebum to limit bacterial growth and sebum fatty acids are fungistatic
, urine, blood, saliva
Nitric oxide (NO) released by macrophages inhibit ATP production
Iron-binding proteins in blood block microbial reproduction
Serum proteins activated in a cascade.
Results:
• Opsonization
• Chemotaxis
• Transmembrane channel formation in cells tagged by antibodies (causing cytolysis)
• Triggers inflammation
The Complement System
Figure 16.10
Body Defenses: Innate and AcquiredDefense 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
(Innate immunity)
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”
Acquired Immune System – Third Line of Defense
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
The Acquired Immune System is:
Types of Acquired Immunity
1. Humoral Immunity
• Antibody-mediated immunity in blood and lymph
• Cells produce chemicals for defense
2. Cellular immunity of the Cell-Mediated 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
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 Receptor in the
immune system that "fits" the
antigenic determinant
Antigen
Antigens
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
B Cell Receptors, T Cell Receptors, and Immunoglobulins
B cell
Secreted (Exported) Immunoglobulin or
Antibody (Same V and C Regions as in B cell
receptors)
Variable (binding
) regions
Receptors on T Cells
Constant
regions
Receptors on B cells
T cell
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
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
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 Precipitation (soluble antigens)
Transmembrane channel
formation and lysis
Antibody Function movie
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
Types of T Cells Cytotoxic T (Tc) cells
• Specialize in killing infected cells
• Insert a toxic chemical (perforin)
Helper T (TH) cells
• Recruit other cells to fight the invaders
• Interact directly with B cells
Suppressor T cells
• 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
Helper t cells animation
Cytotoxic t cells animation
Summary of B Cell Activation
B cells can be activated directly by antigen or from a TH cell activated by an antigen-presenting macrophage
Organ Transplants and Rejection Major types of grafts
• Autografts – tissue transplanted from one site to another on the same person
Hey buddy, my patch of skin is damaged! Can I have your autograft?
• 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)
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