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Immunity
Anatomy & Physiology
Tony Serino, Ph.D.
Biology Department
Misericordia Univ.
Immune System
• Provide defense of the body against
infectious agents, toxins, foreign bodies,
and cancers
• Two types of defenses:
– General (Non-specific or Innate) Defense
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Barriers
Normal Flora and Fauna
Fever
Surveillance
Inflammation
Non-specific Phagocytic WBCs and NK cells
Protective Chemicals
– Specific (Adaptive) Defense --Lymphocytes
Barriers
• Prevent infectious agents from penetrating
internal environment
– Epithelium ( thickness, tight junctions, keratin)
-especially the skin
– Cilia and mucus
– Watery secretions (tears, saliva)
– Acidity (stomach, urine, vaginal secretions)
• Normal Flora and Fauna –resident bacteria
prevent infectious agents from growing on
body surfaces
Fever
• Rise in Body Temperature
– Inhibits invading cell growth; increase body
metabolism to increase defense/repair cell activity
– Produced by release of pyrogens from leukocytes
– Low grade fever is beneficial in fighting infection,
high sustained fever may be life threatening
Surveillance
• Number of cells and organs to detect invading
agents
• Langerhans cells of skin, Mast cells, Dendritic
cells, and organs like: Tonsils, GALT cells
• Gather antigens and present them to
lymphocytes
Inflammation
• Allows more blood defenses into damaged areas
• Triggered by release of paracrines from damaged
tissues (PG), attacking WBCs (cytokines), mast
cells (heparin and histamine), and activation of
blood protective chemicals (complement and
bradykinins)
• Increases:
– blood flow through vasodilation (hyperemia)
– capillary permeability
– Both lead to local edema
• If prolonged or systemic, can become life
threatening
Inflammatory Response
Phagocytic WBC and NK cells
• WBCs can distinguish the sugars in
mammalian cells and those found on
bacteria or other parasites
– PMNs, macrophage, and mast cells can injure
or destroy cells that do not display normal
sugars
• NK cells –related to T-cells but attack any
cell not displaying MHC I proteins
– Kill by secreting perforins and other chemicals
Phagocytosis
Protective Chemicals
• Chemicals that aid in destroying or
retarding infectious agents
– Interferon –cytokine released when cell
attacked by virus; warns other cells in area
– Lysozyme –antibacterial enzyme present in
tears and saliva
– Complement –blood proteins which can detect
and destroy bacteria
Interferon
Complement
MAC –membrane
attack complex
(C3-C9)
Specific (Adaptive) Immunity
• Individual targets are selected for attack by the
lymphocytes that can bind that target (antigen)
• Antigens (Ag) – any large substance not normally
found in the body; these illicit an immune
response (immunogenic and immuno-reactive)
• Haptens are small molecules that can trigger an
immune response only if bound to larger
molecules (like: pollen, some cosmetics,
detergent fragrances, poison ivy animal dander
and drugs); they are immuno-reactive but not
immunogenic by themselves
Antigenic Determinants
Large macromolecules illicit immune
response because they have many sites to
which immune molecules will attach;
proteins have the most of any molecule
Identifying “Self” from “Non-self”
• T-cells migrate to thymus, B-cells remain in bone
marrow (the primary lymphoid tissues)
• Become immunocompetent -selected for their
ability to produce a surface receptor against an
antigen and to tolerate self antigens
• Those that bind weakly to self-antigens are
selected, the others are eliminated
• The strongest self-antigens are the MHC proteins
• Once competent, the cells are released to move
through the blood and aggregate in the secondary
lymphoid tissues
Thymic Selection
Movement of Lymphocytes
Cells Involved in Specific Immunity
• Lymphocytes (B and T cells) -attack antigen
bearing agents either chemically (humoral
immunity –the B-cells) or physically (cellular
immunity –the T-cells)
• T and B-cell activation to an antigen works best
when they are presented with the antigen by
another cell
• APCs (Antigen Presenting Cells) (macrophage,
surveillance cells, B-cells, infected cells) display
foreign antigenic determinants on their MHC II
cell surface proteins to activate the lymphocytes
Memory
T cell
B-cell Clonal Expansion
Antibody Structure
Antibody Actions
Opsonization –
Ag-Ab complex
makes ID for
phagocytosis
easier
Humoral Response
Control of Lymphocyte Response
• B-cells can be activated by the antigen alone, but
it is more effective if they are presented the
antigen by APCs or stimulated by T-helper cells
• Activation of T-helper cells stimulates complete
lymphocyte response
MHC I –found on all body’s cells except RBCs
Surface proteins usually bound to pieces of intracellular
proteins, but when infected they present fragments of the
infectious agent
MHC II –found on APCs
-bound to phagocytized outer coat molecules of immuno-agent
T-cell Types
Helper T-cells
Clonal Selection of T-cell
Cytotoxic T-cell Attack
Primary Immune Response
Vaccine Production
Types of Acquired Immunity
Acute Allergic Reaction
Pathologies
• AIDS –HIV invades T-helper cells, diminishing
effectiveness of immune response; may have as
long as 8 year incubation time, 100% fatal
• Autoimmune Diseases –Immune system targets
naturally occurring compounds of the body
(usually sequestered proteins) MS, rheumatoid
arthritis, Diabetes mellitus (I), etc.
• Cancer –cancers cells spontaneously form during
life, but the immune system keeps them in
check; failure results in tumors and metastasis