The document provides an overview of the immune system presented by Dr. Sadaf Moeez. It defines key terms like immune system, immunology, immunity, and immune response. It describes the immune system as the cells, tissues, and molecules that mediate resistance to infections. The key tasks of the immune system are recognition of infections, effector functions to eliminate infections, regulation to prevent damage to the body, and memory to generate a strong secondary response. The document also discusses immunity, pathogens, antigens, types of immunity including innate and acquired, and antigens including exogenous and endogenous antigens.

1. OVERVIEW OF
IMMUNE SYSTEM
BY: DR SADAF MOEEZ
LECTURE 1

2. Definitions
• Immune system = cells, tissues, and molecules that mediate resistance to
infections •
• Immunology = study of structure and function of the immune system
• Immunity = resistance of a host to pathogens and their toxic effects
• Immune response = collective and coordinated response to the
introduction of foreign substances in an individual mediated by the cells
and molecules of the immune system

3. What is Immune System
• It is a biological structures and processes within an organism
that protects against disease by identifying and killing
pathogens and tumor cells.
• It detects a wide variety of agents, from viruses to parasitic
worms, and needs to distinguish them from the organism's own
healthy cells and tissues in order to function properly.

4. Key Tasks of the Immune System
• Recognition – detect the presence of an infection.
• Effector functions – contain the infection and eliminate it completely –
Antibodies – Cytotoxic lymphocytes
• Regulation – immune response must be kept in check so it doesn’t damage
the body – Autoimmune disease – Allergy
• Memory – generate an immediate and strong secondary response to
protect the individual against recurring disease due to the same pathogen

5. Immunity
• The Latin term “IMMUNIS” means EXEMPT, referring to protection against
foreign agents.
• DEFINITION: - The integrated body system of organs, tissues, cells & cell
products that differentiates self from non – self & neutralizes potentially
pathogenic organisms.
• Immunology is the study of our protection from foreign macromolecules or
invading organisms and our responses to them. • Host – e.g. me!!!! •
• Foreign macromolecule, antigen – e.g. virus protein, worm, parasite (Everything
that should not be in my body)

6. Role of the Immune System
• Defense against microbes
• Defense against the growth of tumor cells – kills the growth of tumor cells
Homeostasis – destruction of abnormal or dead cells (e.g. dead red or
white blood cells, antigen-antibody complex)

8. Immunology
• The study of the body’s defense against infection.
• How does the body eliminate invaders and cure itself?

9. Immunity
• Resistance acquired by a host towards injury caused by microorganisms
and their products. •
• Protection against the infectious diseases is only one of the consequences
of the immune response, which entirely is concerned with the reaction of
the body against any foreign antigen.

10. What causes Disease?
• At the time vaccinations started in the late 1700’s, nothing was known
about what caused disease.
• In the late 1800’s, Robert Koch proved that microorganisms are
responsible for particular diseases.
• Pathogen: disease causing organism. – Four main types today: viruses,
bacteria, fungi, and unicellular and multicellular parasites.

11. The search for an answer
• Scientists asked, “how are vaccines offering protection? What is the
mechanism?”
• 1890’s: serum of animals immune to tetanus contains antitoxic activity that offers
short-lived protection against tetanus toxins in people –
• Discovery of antibodies! Antibodies bound specifically to the toxins and
neutralized their activity. –
• The toxins are antigens.
• Antigen = substance that stimulates antibody generation.

12. Types of Immunity
• Its classified as
• Innate immunity (Native)
• Non specific: species, racial, individual
• Specific: Species, racial, individual
• Acquired Immunity (Adaptive)
• Active: Natural or Artificial
• Passive: Natural or Artificial

13. Types of Immunity
• Two types of immunity
• 1. Innate (non-adaptive) – first line of immune response
• relies on mechanisms that exist before infection
• 2. Acquired (adaptive) – Second line of response (if innate fails)
• relies on mechanisms that adapt after infection
• handled by T- and B- lymphocytes
• one cell determines one antigenic determinant

15. Antigen
• ANTIGEN: An antigen is a molecule that induces an immune response in
the body.
• Origin of antigen
• Exogenous antigens • Antigens that have entered the body from the
outside. E.g. By inhalation, ingestion, or injection.
• Endogenous antigens • Antigens that have been generated within
previously normal cells as a result of normal cell metabolism, or because
of viral or intracellular bacterial infection

18. Immunogen