Introduction and Types of immunology

1. Atifa Ambreen
M. Phil, Microbiology
Government College University, Faisalabad

2. What is Immunology?
➢ Immunology is a branch of biology that covers
the study of immune systems in all organisms.
or
➢The study of the body's defenses is
called
immunology.
or
➢ A science that deals with the immune system
and the cell-mediated and humoral aspects of
immunity and immune responses.

3. The immune system is typically associated with
defending against foreign intruders (unwanted
attack), called pathogens, but it can fight against
various disorders including metabolic,
cardiovascular, and neurodegenerative conditions
such as Alzheimer’s. The immune system protects
us from infection through various lines of defence.
➢ If the immune system is not functioning as it
should, it can result in various diseases, such as
autoimmunity, allergy and cancer etc.

5.  The immune system has been divided into
I. Innate immune system
II. An acquired or adaptive immune system
 This is further divided into
➢ humoral (or antibody)
➢ cell-mediated immunity

6.  Innate immunity is the first line of defence and is non-
specific. That is, the responses are the same for all
potential pathogens, no matter how different they
may be. Innate immunity includes physical barriers
(e.g. skin, saliva etc.) and cells (e.g. macrophages,
neutrophils, basophils, mast cells etc.) These
components ‘are ready to go’ and protect an organism
for the first few days of infection. In some cases, this is
enough to clear the pathogen, but in other instances
the first defence becomes overwhelmed and a second
line of defence kicks in.

7.  Adaptive immunity is the second line of defence
which involves building up memory of
encountered infections so can mount an
enhanced response specific to the pathogen or
foreign substance. Adaptive immunity involves
antibodies, which generally target foreign
pathogens roaming free in the bloodstream. It is
based on B-cells and T-cells, which are directed
especially towards pathogens that have
colonized cells and can directly kill infected cells
or help to control the antibody response.

8.  Antigen: An antigen is a substance that ignites the immune
response.The cells involved in recognizing the antigen are
Lymphocytes. Once they recognize, they secrete antibodies.
 Antibody: Antibody is a proteins that neutralize the disease-
causing microorganisms. Antibodies don’t directly kill
pathogens.The humoral (antibody) response is defined as the
interaction between antibodies and antigens.

 Allergenicity: Allergenicity or allergenic potential: the potential of
a material to cause sensitisation and allergic reactions, frequently
associated with IgE antibody.


9.  Cell-mediated immunity is an immune response that does
not involve antibodies. Rather, cell mediated immunity is
the activation of phagocytes, antigen-specific cytotoxicT-
lymphocytes, and the release of various cytokines in
response to antigen.
 Autoimmunity

 Autoimmunity is the system of immune responses of an
organism against its own healthy cells and tissues. Any
disease that results from such an aberrant immune
response is termed an "autoimmune disease".


10.  The cells of the immune system can be categorized
as:
➢ lymphocytes (T-cells, B-cells, Mast cells and NK
cells)
➢ neutrophils, and monocytes/macrophages
 These are all types of white blood cells. The major
proteins of the immune system are predominantly
signaling proteins (often called cytokines),
antibodies, and complement proteins.