A Brief History
Immunology is the study of body’s defense against infection
• Edward Jenner- 18th centaury
→ Observed that the relatively mild disease, cowpox (vaccinia) offered some protection against the
more fatal smallpox (variola).
→ He called this inoculation of a healthy person with an attenuated or weakened form of a disease
in order to give protection against the disease –vaccination
→ It took almost two centuries before this vaccination became commonplace,
with the WHO announcing in 1979 that smallpox had been eradicated.
• Robert Koch- Late 19th centaury
→ Discovered that microorganisms cause disease.
→ We now recognise: viruses, bacteria, fungi and parasites as disease causing
• Louis Pasteur- 1880
→ Developed cholera & rabies vaccine
• Emil von Behring & Shibasaburo Kitasato- 1890
→ Discovered that animals immune to diphtheria or tetanus exhibited a serum with antitoxic activity
that gave short-lived protection against these diseases in people.
→ We now know that these compounds are antibodies which bind to antigens and mark them for
destruction
• Elie Metchnikoff- 1890
→ discovered that the body has cells capable of engulfing and destroying microorganisms.
→ He termed these cells macrophages.
→ Discovered macrophages
→ It was later discovered that antibodies could be induced against many substances.
→ These substances were termed antigens since they could induce antibody generation
→ The term antigen is now used to describe any substance that can illicit an immune response
TJW Notes
,• Histologically this system consists of a large, diverse population of leukocytes located within every tissue
of the body and lymphoid organs interconnected only by the blood and lymphatic circulation
• Immunologists recognize two partially overlapping lines of defense against invaders and/or other
abnormal, potentially harmful cells: innate immunity and adaptive immunity
• An effective immune system in vertebrates is capable of:
→ Immunological recognition
⤷ Detecting the presence of an infection
→ Immune effector function
⤷ Containing and possibly eliminating the infection
→ Immune regulation
⤷ The response has to be controlled to prevent damage to the body
⤷ Tolerance of self-antigens to prevent induction of auto-immune reactions
• Immunological memory
This is a unique feature of the adaptive immune system in which having been exposed to a pathogen, a
memory of it is retained, allowing the second exposure to the pathogen to elicit a quicker and stronger
immune response against it
• Development of cells
→ Cells originate in the bone marrow
→ Develop and mature in bone marrow or in the primary lymphoid organs
→ From haematopoietic stem cells (pluripotent) in the bone marrow, note the myeloid and lymphoid
lineages developing
→ The adaptive immune system undergoes further development in the primary lymphatic organs:
~ Antigen-independent differentiation
→ When adaptive immune cells encounter an antigen:
~ Undergo antigen-dependent differentiation
TJW Notes
, INTRODUCTION
• The body has a system of cells—the immune system—that has the ability to distinguish "self" (the
organism's own molecules) from "non-self" (foreign substances).
• This system has the ability to neutralize or inactivate foreign molecules (such as soluble molecules as well as
those present in viruses, bacteria, and parasites) and to destroy microorganisms or other cells (such as virus
infected cells, cells of transplanted organs, and cancer cells).
• On occasion, the immune system of an individual reacts against its own normal body tissues or molecules,
causing autoimmune diseases.
• The cells of the immune system:
(1) are distributed throughout the body in the blood, lymph, and epithelial and connective tissues
(2) are arranged in small spherical nodules called lymphoid nodules found in connective tissues and
inside several organs
(3) are organized in larger lymphoid organs—the lymph nodes, the spleen, the thymus, and the bone
marrow.
→ Lymphoid nodules are isolated cells of the immune system found in the mucosa of the digestive system
(including the tonsils, Peyer’s patches, and appendix), the respiratory system, the reproductive system, and
the urinary system are collectively known as mucosa-associated lymphoid tissue (MALT) and may be
considered a lymphoid organ.
→ The wide distribution of immune system cells and the constant traffic of lymphocytes through the blood,
lymph, connective tissues, and lymphoid organs provide the body with an elaborate and efficient system of
surveillance and defense
TJW Notes
