N5315 Advanced Pathophysiology
Inflammation, Altered Immunity and Infection
Core Concepts Objectives with Advanced Organizers
Immune System
1. Examine the structure and function of the immune system.
• Natural Immunity (AKA Innate Resistance/ImmuNatural immunity is provided by
nonspecific barriers to infection such as the skin, mucous membranes, certain cells (NK
cells), certain proteins (complement, cytokines), and involves inflammation and
phagocytosis. It does not improve after exposure. It functions to kill invading
microorganisms and activates acquired immunity. The cells of innate immunity include
phagocytic cells, antigen presenting cells, natural killer cells, and complement. nity). This
is resistance that exists prior to exposure to a microbe.
• The bone marrow, thymus, spleen, lymph nodes, tonsils and peyer patches all have a role
in immunity. The bone marrow is responsible for the production of immune cells and the
maturation of B cells. As we grow, the thymus shrinks, but it provides a site for T -cell
differentiation, maturation and selection. The spleen is a lymphoid organ and contains
blood filled sinuses which filter antigens and cells from the blood. The red pulp is the
location of red blood cell storage and turnover. The white pulp is the site where immune
cell interaction occurs. Antigen presenting cells present antigens to the lymphocytes in
the spleen which triggers the immune response. Persons who have had their spleen
removed or have a nonfunctional spleen as is the instance with persons with sickle cell
disease are at an increased risk for infection, particularly infections caused by
streptococcal bacteria. These individuals require the pneumococcal vaccine. The lymph
nodes, tonsils, and peyer patches are also sites where antigens interact with immune cells.
Phagocytic cells include neutrophils, macrophages, and dendritic cells.
• ▪ Neutrophils are present during acute inflammation and are responsible for engulfing
microbes and kills them by using a cytoplasmic myeloperoxidase which is toxic to
pathogens.
• ▪ Macrophages are derived from monocytes, which leave the blood stream and
differentiate in tissues.
• Dendritic cells engulf antigens in the epithelia of the skin, GI and respiratory tracts.
a. Evaluate how the normal function of T-lymphocyte and B-lymphocyte cells
differ.
• While B-cells produce antibodies to fight infection, T-cells protect people from
getting infected by destroying cancerous and infected cells.
b. Differentiate between the function of humoral and cell mediated immunity.
• Humoral immunity is that immunity conferred by the B-Cells. It provides immunity
against some viral infections, toxin induced diseases and diseases caused by
pneumococci, meningococci, or Haemophilus.
• Cell-Mediated immunity is that immunity conferred by T-Cells. Immunity is active
against cells infected with intracellular bacteria or viruses. It defends against cancer,
fungal infections, parasitic infections, tumors, and is responsible for organ transplantation
rejection.
, c. Analyze the difference between active acquired immunity and passive
acquired immunity.
• Acquired Immunity is the state of immunity that is obtained after exposure to an antigen.
It improves with repeat exposure and it is specific. Active acquired immunity is produced
by the host after exposure to an antigen or an immunization. This is the basis of
vaccinations.
• Passive acquired immunity is that immunity acquired via the transfer of antibodies, or T-
cells to the recipient. Natural Passive immunity occurs via mother to fetus. Antibodies
cross the placenta or in the breast milk. Artificial Passive Immunity occurs when
antibodies are given to a recipient to provide immunity. This is used to treat rabies,
tetanus, hepatitis, and snake bites. It is a good way to fight infection, it provides
immediate protection, but the immunity only lasts as long as the antibodies,
approximately 2 weeks.
d. Define the following terms:
Antigen
Antigen presenting cells include dendritic cells, macrophages and B cells. APC ingest and
process antigens. The peptides are loaded on to their major histocompatibility complex II
molecule and are presented to the Tcell. Antigen presenting cells present antigens to the
lymphocytes in the spleen which triggers the immune response
Self-antigen
A self-antigen is an antigen that the immune system derives from the body it is protecting. For
example, a heart cell, a liver cell, and a kidney cell would all contain self-antigens. A healthy
immune system tolerates self-antigens and does not attack them. NORMALLY PRESENT!!!
Allergens
An allergen is a type of antigen that produces an abnormally vigorous immune response in which
the immune system fights off a perceived threat that would otherwise be harmless to the body.
e. Evaluate the function of antibodies produced by the B-lymphocyte cells.
The overall functions of antibodies include the neutralization of bacterial toxins. They coat
the bacteria to enhance phagocytosis and form antigen antibody complexes which activates
the complement cascade.
Type of B- Function
Lymphocyte
Cells
IgA IgA is the main immune globulin in secretions and mucous membranes. It prevents the attachment of
microorganisms to the mucous membranes.
IgM IgM is the main immune globulin produced early in the primary immune response. A high level of IgM
antibodies indicates a recent infection.
IgG IgG is the most prominent immune globulin. It binds with viruses, bacteria and toxins. It activates
complement and binds to macrophages. It is the primary antibody in the secondary immune response.
Levels rise in response to subsequent exposure to an antigen. It is the only immune globulin that crosses
the placenta.
IgE IgE binds to mast cells, eosinophils and basophils. It is involved in parasitic infections and
hypersensitivities reactions.
IgD IgD is found on the surface of B-lymphocytes. It signals B-cell activation.
, Type of T- Function
lymphocyte Cells
T-cytotoxic cells CD8 cells are cytotoxic T-cells, AKA CD8 Cells, Killer T’s, T8 cells. They function to kill virus
infected cells, tumor cells and allograft cells (transplant tissue) directly through the release of
cytotoxic chemicals which destroy the cell membrane or induce apoptosis.
NK Killer cells Natural Killer Cells contain granules that attack and kill virus-infected or cancerous cells.
T-Regulatory cells T-regulatory cells slow or stop the immune response once the invader is defeated
T-Helper cells CD4 cells are aka T-helper or T4 cells. They function to activate macrophages, B-cells,
cytotoxic T-cells and other CD4 cells.
Type of Cell Role in the Processing of Antigens
B-Lymphocytes B-cells stimulated by the release of IL4 → B-cells differentiate into plasma cells → produce
antibodies and memory B-cells
Plasma cells will produce antibodies that will bind to the antigen and make antigen-antibody
complexes
Memory B-cells will act during secondary immune response and will remember the antigen. This
memory will serve to trigger the production of antibodies much sooner during the secondary immune
response than during the primary immune response.
T-lymphocytes Antigen presenting cells include B-lymphocytes, macrophages, and dendritic cells.
• Antigen enters host → Macrophage (or other APC) engulfs antigen → antigen expressed on MHC
class II → secretes IL 1 to attract CD4 cells → presents it to CD4-cells → CD4 differentiates into Th1
and Th2→ Th1 releases IL2 → activated cytotoxic T-cells (Tc) → Tc receptor connects with MHC
class I receptor on invader → cytotoxic chemicals released → invader killed. Th2 releases IL4 →
activates the humoral immune system
f. Differentiate between the role of T-Helper Lymphocytes and B-lymphocytes
in the immune response.
CD4 cells are aka T-helper or T4 cells. They function to activate macrophages, B-cells, cytotoxic
T-cells and other CD4 cells. They release lymphokines that begin the inflammatory process and
they mediate delayed hypersensitivity reactions such as the TB skin test. These functions are
performed by a subgroup of CD4 cells called TH1 and TH2. These are the cells that release
lymphokines.
B-cells mature into plasma cells that then produce antibodies. The overall functions of antibodies
include the neutralization of bacterial toxins. They coat the bacteria to enhance phagocytosis and
form antigen antibody complexes which activates the complement cascade.
2. Analyze the process and purpose of the primary and secondary immune responses.
Upon initial exposure to an antigen, the immune system will mount a response within 5-7 days.
This response is called the primary immune response and is characterized by a rise of IgM
antibodies and later in the course of an infection a rise in IgG antibodies. The next time the
immune system is exposed to the same antigen, a secondary immune response is mounted. This
is also called an anamnestic immune response. IgM levels rise during this response, but IgG
levels rise much more than in a primary immune response.
IgM levels are elevated early in an infection and IgG levels are elevated later in an infection
IgG antibodies are what provide us with long lasting immunity.
A good example of this principle is chicken pox. A child who gets infected with chicken pox
mounts a primary immune response, because that is the first they were exposed to the antigen
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