IMMUNOLOGY AND SEROLOGY

DVT2153Lecture I

Universiti Malaysia kelantanFaculty oF veterinary medicine

Dr. Erkihun Aklilu2/13/2012 1

IMMUNOLOGY

Immunology:

The study of organisms’ body protection from foreigninvading/disease causing microorganisms.

The study of mechanisms by which an animals/humanbody is protected from infectious agents or foreignsubstances.

A science that deals with the immune system and the cell-mediated and humoral aspects of immunity and immuneresponses (Merriam Webster Dictionary)

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ImmunIty

What is immunity?

Immunis (Latin) for "exempt“

Exempt: Free from an obligation or liability imposed on others.

Immunity: the state of being exempted(excluded/freed/absolved/excused /relieved). E.g. from disease/infection.

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Brief History of Immunology 12th century Chinese observation

Deliberately infected infants with scabs fromsmallpox lesions: Variolation– Less mortality– Protection from further infection

Concepts of variolation spread to Europe

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Brief History of Immunology

Rinderpest (Cattle Plague): Heavy loss ofcattle population through out Europe forhundreds of years

Vague similarity of lesions between Smallpoxand Rinderpest diseases Possibility of variolation suggested (1794) Soaking of small strings in the nasal discharge of

an infected cow Insert into an incision in the dewlap of healthy

animals- The practice became very popular2/13/2012 5

Brief History of Immunology In 1798, Edward Jenner (an English Physician) demonstrated

that a scab from a cowpox lesion can replace smallpox scabs for variolation.

Dramatically reduced the risks of variolation with smallpox dramatically

This procedure was called: Vaccination (from ‘Vacca’ for cow in Latin).

Eventually led to the eradication of smallpox from the world in 1970s

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Brief History of Immunology Once variolation was accepted similar

approaches were used

Ovination: To protect sheep from sheep pox

Bovine pleuropneumonia: A piece of tissuefrom infected lung was inserted into anincision in the tail- tail falls off and theanimal gets immuned

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Brief History of Immunology

• Louis Pasteur (1879) investigated Fowl cholera(caused by Pasteurella multocida)

• Birds inoculated with old P. multocida cultures wereresistant when challenged by the same bacteria fromfresh culture. Louis Pasteur’s Investigation.ppt

• A breakthrough!

• Pasteur also developed Anthrax vaccine, Rabiesvaccine

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Brief History of Immunology Daniel Salmon and Theobald Smith from US

demonstrated that dead organisms can also beused for immunization.

Heat-killed isolates of Salmonella choleraesuis(Bacillus suipestifer) were used to protect pigeonsfrom hog cholera

Von Behring and Kitasato from Germany showedthat filtrates from cultures of Clostridium tetanicould protect animals from tetanus.

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The Immune System• The immune system is composed of many

interdependent cell types that collectively protectthe body from infectious agents (bacteria,parasite, fungi, virus) and from the growth oftumor cells.

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The Immune System

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

In vertebrates a highly specialized receptors fordiscriminating between ”self” and “nonself”body components

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The Immune System

Specialized receptors for discriminating between ”self” and “nonself” substances

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The Immune System Produces coordinated response to the introduction of

foreign substances or antigens into the body Organizationally divided into two complementary arms:

– The Innate (Native or Natural) Immune System– The Adaptive (Acquired or Specific) Immune System

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Innate Immune System Provides the body’s early line of defense against

microbial invaders

Comprises four types of definitive barriers

– Anatomic or Physical (skin, mucous membranes)

– Physiologic (temperature, pH, and chemicals such aslysozyme, complement, and some interferons)

– Phagocytic (monocytes, neutrophils, macrophages)

– Inflammatory events

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Innate Immune SystemCommon characteristics of innate immune

defenses

– Present intrinsically (with or without previousstimulation)

– Have limited specificity for shared structures ofmicrobes

– Are not enhanced in activity via repeated exposure

– Have limited diversity of expression

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Adaptive/Acquired Immune System

• Once the barriers of the immune response havebeen breached, the adaptive immune system isactivated

• Acquired immune system is activated inantigen-specific fashion to eliminate antigensand provide lasting protection

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Adaptive/Acquired Immune System

Components of the Adaptive Immune System

Lymphocytes • T cells and B cells• Plasma cells (end cells of B-lymphocyte differentiation)

Antigen-presenting cells (Macrophages, B cells, and dendritic cells)

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Adaptive/Acquired Immune System

Common Characteristics

Specific for particular antigen and are specialized toprovide the best protection

Diverse in their specificity

Enhanced with each repeated exposure (i.e. expressimmunologic memory)

Capable of self/non-self recognition

Self-limiting

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Comparisons Between Innate Immune System and Adaptive Immune System

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Interaction Between Innate Immune System and Adaptive Immune System Innate and adaptive immune systems do not

operate independently of each other:

– Phagocytic cells process and display antigen tofacilitate stimulation of specific T-lymphocytes

– Macrophages secrete immunoregulatory molecules(cytokines), which help trigger the initiation of specificimmune responses

– T-lymphocyte produce cytokines, which enhance themicrobial activities of phagocytes

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Interaction Between Innate and Adaptive Immune Systems

Antibodies produced by plasma cells bind topathogens and activate the complement systemto result in the destruction of the invaders

Antibodies produced by B-lymphocytes bindto pathogens and assist with phagocytosis(opsonization)

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Interaction Between Innate and Adaptive Immune Systems

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SerologyWhat is Serology?

The branch of laboratory medicine that studiesblood serum for evidence of infection and otherparameters by evaluating antigen-antibodyreactions in vitro

Serology is the scientific study of blood serum. Inpractice, the term usually refers to the diagnosticidentification of antibodies in the serum (possibleto detect antigens as well)

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Serology Serology as a science began in 1901.

Austrian American immunologist KarlLandsteiner (1868-1943) identifiedgroups of red blood cells as A, B, and O.

From that discovery came therecognition that cells of all types,including blood cells, cells of the body,and microorganisms carry proteins andother molecules on their surface that arerecognized by cells of the immunesystem.

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History of Serology

Karl Landsteinar (1868-1943) An Austrian physician,

Landsteiner played an integralpart in the identification ofblood groups.

He demonstrated thecatastrophic effect of transfusingwith the wrong type of blood,

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Applications of Serology HIV testing Serum HCG (pregnancy) Tests for hepatitis antigens and

antibodies Antibodies to bacteria Hepatitis serology Various animal diseases (e.g

Brucellosis) For epidemiological studies Differentiate vaccinated vs

unvaccinated/infected animals2/13/2012 27