Immunology is the study of the immune system and its functions. The immune system protects the body from pathogens and other foreign substances. It has both innate and adaptive immunity. Innate immunity provides immediate defenses while adaptive immunity involves memory cells that mount stronger, pathogen-specific responses. The immune system is made up of cells like lymphocytes, neutrophils, and macrophages that recognize antigens and trigger antibody and cell-mediated responses to protect health. When it malfunctions, autoimmune diseases can occur.

1. Essentials of Immunology
Dr. Farheen Bhatti
PhD (Biotechnology)
Lecture-1

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. When an Immune System Triggers?
 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. Categories of Immune System
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 and second lines 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 (first-line of defense) includes
physical barriers (e.g. skin, saliva etc.) and cells (e.g.
macrophages, neutrophils, basophils, mast cells etc.)
include second line of defense. 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.
Innate Immunity

7. Adaptive immunity is the third 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 colonised cells and can directly kill
infected cells or help to control the antibody response.
Adaptive Immunity

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.
The humoral (or 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 cytotoxic
T-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".
Cell Mediated Immunity

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.
The Cells of Immune System

11. Innate Immunity vs Adaptive Immunity

12. Types of Adaptive Immunity