Name: Gelene Eriel B. Tamparia
Year & Section: BSN – 1C
LEARNING OBJECTIVES:
CHAPTER 9: HOST RESPONSE TO INFECTION
1.) Differentiate "antigen" from "immunogen;"

Antigen is a substance recognized by the immune system, whether by the B
cell or the T cell, that serves as the target of the immune response but may
not necessarily lead to an immune response.

On the other hand, Immunogen are any subtances that is capable of
inducing an immune response, whether humoral or cell-mediated or both.
2.) Discuss the properties of antigen that would make them immunogenic;
There are several properties that an antigen must possess to make it
immunogenic. These include: 1) foreignness and genetic composition; 2) chemical
composition and complexity; 3) molecular size and stability; and lastly, 4) mode of
entry of the antigen.
3.) Describe the different lines of defense of the body;
The immune system's three lines of defense include; 1.) Physical and
Chemical Barriers. This includes the skin, fatty acids in sebaceous secretions, and
sweat. It acts as the first line of defense serve to prevent entry of organism; 2.) Nonspecific innate responses. This innate immune response mostly involves immune
cells and proteins to non-specifically recognize and eliminate any pathogen that
enters the body; 3.) Immune response. This involves the B cells and T cells, cells that
are involved in adaptive immunity.
4.) Determine the role of the B cells and T cells in providing defense against
infectious agents;
B Cells

Involved
in
T Cells
the
body's

humoral immunity

Involved in the body’s cell-mediated
immunity.
Differentiate into antibody-

producing plasma cells as
Further differentiate into CD4+ T and
CD8+ T cells (cytotoxic or cytolytic).
well as memory B cells

They
function
professional
as
a

antigen
The helper T cells do not have the direct
capacity to destroy an antigen. Instead, it
presenting cell.
activates
the
cytotoxic
T
cells
and
stimulates differentiation of B cells into
antibody-producing plasma cells.

The regulatory T cells play an important
role in the maintenance of self-tolerance
or the ability of the immune system to
recognize self from non-self.
5.) Differentiate innate immunity and adaptive immunity;

Innate immunity is also known as natural immunity. This immunity is already
active from the time of birth, prior to exposure to an antigen. It is nonspecific, acts immediately upon encounter with the antigen but gives shortterm protection. It includes the body's first and second line of defense.

On the other hand, Adaptive immunity is activated but certain antigens
which makes the response more specific. It has a more delayed reaction
because it takes time for antibodies to be produced and for cytotoxic T cells
to be activated. The protection obtained is long-term and in most instances,
lifelong. It constitutes the body's third line of defense.
6.) Identify the differences b/w humoral and cell-mediated immune response;
- The major difference b/w humoral and cell-mediated immunity is that
humoral immunity produces antigen-specific antibodies, whereas cell-mediated
immunity does not.
7.) Examine the functions of the different immunoglobulins;
The major classes of immunoglobulins:
• IgM - primary response, fixes complement. Monomer serves as B cell receptor.
• IgG - Main blood antibody, neutralizes toxins, oposonization.
• IgA - Secreted into mucus, tears, saliva.
• IgE - Antibody of allergy and anti-parasitic activity.
• IgD - B cell receptor.
8.) Differentiate primary immune response and secondary immune response;
- The primary immune response displays the first contact of the immune
system with an infectious agent whereas; all following contents with the same
pathogen are named secondary immune response.
9.) Distinguish from each other the mechanisms involved in the various types of
hypersensitivity reactions, citing examples for each type; and

Type I: Immediate Hypersensitivity
- the effector cells are mast cells and the predominant inflammatory cells are
the eosinophil.
- Examples are atopic diseases & allergic diseases

Type II: Antibody-mediated Hypersensitivity
-
It is triggered by antigen-antibody complexes that causes activation of the
classical pathway of complement system.
-
Examples of conditions under this mechanism are transfusion reactions,
blood incompatibilities & autoimmune haemolytic anemias.

Type III: Immune Complex-mediated Hypersensitivity
- It is also triggered by antigen-antibody complexes. The main difference is
the site of formation of immune complexes and the resulting deposition of
theses complexes in tissues and blood vessels leading to fibrinoid necrosis.
- Examples are drug-induced serum sickness, systemic lupus
erythematosus, farmers' lung (hypersensitivity pneumonitis), and
rheumatoid arthritis.
 Type IV: T Cell-mediated Hypersensitivity
- It is the T cell-mediated hypersensitivity reaction which involves either
CD4+T cells (delayed type hypersensitivity) and CD8+ T cells (cytotoxic T
cell-mediated).
- Examples include contact dermatitis, poison ivy, tuberculin skin test, and
certain drug reactions, such as allopurinol.
10.) Explain the role of vaccines in the prevention of the development of
infectious diseases.
- Vaccines are designed to stimulate the body’s immune system to produce
the antibodies specific to the organism or its components so that these are
recognized as foreign and will be destroyed immediately upon entry of the
organism into the body.