The term immunity is derived from the Latin

word immunitas.

Historically, immunity meant protection

from disease and, more specifically,

infectious disease.

is the study of immunity and the

cellular and molecular events that

occur after an organism encounters

microbes and other foreign

macromolecules.

• Study of the components and function of the

immune system

Immune System › Molecules, cells, tissues and organs which

provide non-specific and specific protection against

Microorganisms

Microbial toxins

Tumor cells

› Crucial to human survival

The immune system must be able to: differentiate between material that is a normal component of the body (“self”) and material that is not native to the body “nonself”

A highly specialized receptors present for discriminating between ”self” and “nonself” body components

The physiologic function of

the immune system is

defense against infectious

microbes.

The cells and molecules responsible for

immunity constitute the immune system,

and their collective and coordinated

response to the introduction of foreign

substances is called the immune response.

A network of cells and tissues that:

1. Defends the body against invading pathogens

2. Removes ‘worn-out’ cells !!!

3. Destroys abnormal/mutant cells within the body

(e.g. control of cancer)

Immune System can also have harmful effects:

1. Allergies

2. autoimmune diseases

3. Tissue rejection.

As mention before, immune response

is the collective and coordinated

response of the immune system to the

introduction of foreign substances.

There are two types of immune

response:

1. Non-specific Immune responses

2. Specific Immune responses

Our Immune system involves the interplay between our Non-specific and our Specific Immune responses

Non-specific immunities collectively referred to as Innate immunity

Specific immunities are referred to as our Adaptive immunity for which there are 2 branches:

1. Humoral immunity 2. Cell-mediated immunity

* It is the first line of defense

* It is active at the time of infection

• It consists of:

a- protective cellular (WBCs and derivatives)

b- chemical components

Innate or Non-specific or Natural immunity

› is present from birth and is nonspecific.

› consists of various barriers to external organs; e,g,

skin, mucous membranes, macrophages,

monocytes, neutrophils, eosinophils, and the

contents of these cells.

Innate Immune system

First line Second

line

1) Mechanical barriers A- cells 2) Chemical & biochemical inhibitors 1- Natural killer

3) Normal flora 2- Phagocytes

B- Soluble factors C- Inflammatory

barriers

Adaptive or Specific or Acquired immunity › is expressed after exposure to a given

substance and is specific.

› involves specific receptors on lymphocytes and the participation of macrophages for its expression.

› consists of:

a. Humoral immunity, mediated by antibodies

b. Cell-mediated immunity, mediated by lymphocytes

1880’s- Metchnikoff discovered

phagocytic cells that ingest microbes

and particles

Elie Metchnikoff

Components of the immune

system

Components of Human Immune System

Streptococcus pyogenes (Group A Streptococcus)

Klebsiella pneumoniae

Mycobacterium tuberculosis

Ebola virus

Human Immunodeficiency Virus (HIV)

Aspergillus fumigatus

Candida albicans

Cryptococcus neoformans

Ascaris lumbricoides

Plasmodium falciparum

After we understood the

principle of the immune

system, we are now able to

treat and prevent many

diseases.