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Introduction To Immunology

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Title: Introduction To Immunology


1
Introduction To Immunology
  • Dr. yasmeen taj

2
Definition
  • The word Immuis means free from burden and
    immunitas means exemption from government taxes
    and this provided the English terminology
    Immunity.
  • Immunity is a broad definition This is a
    protective or defense mechanism of our body,
    which leads us to a healthy life.

3
Types Of Immunity
  • Inborn or innate immunity It is present at
    birth This is our First Line Of Defense.
  • Acquired or specific It is not present at birth
    but becomes part of our immune system as the
    lymphoid system develops.
  • 1970 WHO defined immunity as immune response to
    antigen ( Foreign body) in form of
  • Humoral ( activation of B-lymhocytes)
  • Cellular (by activation of T-lymphocytes

4
Cells Involved in Immunity
  • Macrophages
  • B cells
  • T cells

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Important components of innate immunityFactors
that limit entry of microorganisms into the body
  • Factor
    Mode Of
    Action
  • -Keratin layer of intact skin
    -Acts as mechanical barrier
  • -Lysozyme in tears and other secretions
    -Degrades peptidoglycan in bacteria

  • cell wall
  • -Respiratory cilia
    -Elevate mucus containing trapped
    organisms
  • -Low pH in stomach and vagina
    -Retards growth of microbes
  • fatty acids in skin
  • -Surface phagocytes
    -Ingest and destroy microbes
  • (eg. alveolar macrophages)
  • -Defensins (cationic peptides)
    -Create pores in microbial membrane
  • -Normal flora of throat, colon
    -Occupy receptors which prevent
  • and vagina
    colonization by pathogens

8
Important components of innate immunityFactors
that limit growth of microorganisms within the
body
  • Natural killer cells
  • Neutrophils
  • Macrophages and dendritic cells
  • Inferons
  • Complement
  • Transferrin and lactoferrin
  • Fever
  • Inflammatory response
  • APOBEC3G (apolypoprotein is RNA editing enzyme)
  • Kill virus infected cells
  • Ingest and destroy microbes
  • Ingest and destroy microbes, and present antigen
    to helper T-cells
  • Inhibit viral replication
  • C3b is an opsonin, membrane attack complex
    creates holes in bacterial membranes
  • Sequester iron required for bacterial growth
  • Elevated temperature retards bacterial growth
  • Limits spread of microbes
  • Causes hypermutation in retroviral DNA and mRNA

9
Macrophages and other antigen presenting cells
such as dendritic cells, participate in both the
innate arm and acquired arm of the immune system.
They are in effect a bridge between the two arms.
As part of the innate arm they ingest and kill
various microbes. They also present antigens to
helper T cells which is the essential first step
in the activation of the acquired arm.
10
Main Components of Innate and acquired Immunity
that contribute to humoral ( antibody-mediated )
immunity and cell mediated immunity
Humoral Immunity Cell mediated Immunity
Innate Complement Neutrophil Macrophages Natural killer cells
Acquired B cells Antibodies Helper Tcells Cytotoxic T cells
11
  • Specificity Of The Immune Response
  • -Recognition of the foreign organisms by specific
    immune cells
  • -Activation of these immune cells to produce a
    specific response (eg,antibodies)
  • -Response that specifically targets the organisms
    for destruction

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Major Functions Of T Cells and B cells
  • Antibody-Mediated Immunity (B Cells)
  • Host defense against infection
  • (Opsonize bacteria, neutralize toxins and
    viruses)
  • Allergy (hypersensitivity) eg, hay fever
    anaphylactic shock
  • Autoimmunity
  • Cell Mediated Immunity
  • 1) Host defense against infection (especially
    M.tuberculosis, fungi and virus infected cells)
  • 2) Allergy (hypersensitivity )eg poison oak
  • 3) Graft and tumor rejection
  • 4) Regulation of antibody response (help and
    suppression)

14
Important features Of Innate and Acquired Immunity
Type of Immunity Specificity Effective immediately Improves Has after exposure to After Exposure memory microbe
Innate Nonspecific Yes in No No minutes
Acquired Highly No--requires Yes Yes specific several days before becoming effective
15
Active and Passive Immunity
  • Active immunity is resistance acquired after
    contact with
  • foreign antigens, eg, microorganisims
  • This contact may consist of
  • Clinical or subclinical infections
  • Immunization with live or killed infectious
    agents or their antigens.
  • Exposure to microbial products (eg, toxins and
    toxoids)

16
Passive immunity
  • Passive immunity is resistance based on
    antibodies preformed in another host.
  • Other forms of passive immunity are IgG passed
    from the mother to the fetus during pregnancy.
  • IgA passed from the mother to the newborn during
    breast feeding.

17
Passive active immunity
  • Passive-active immunity involves giving both
    preformed antibodies (immune globulins) to
    provide immediate protection and
  • Vaccine to provide long term protection
  • These preparations should be given at different
    sites in the body to prevent the antibodies from
    neutralizing the immunogen in the vaccine.
  • This approach is used in the prevention of
  • Tetanus, Rabies and Hepatitis B

18
Immunogen and Antigen
  • When foreign substances (Ag) are introduced into
    the body, they lead to anti-foreign substance
  • ( Anti-body ) formation
  • Immunogenic when they are able to produce
    specific immune response that they will
    stimulate immune cells and then give rise to
    immunological reaction (Humoral or cellular).
  • Antigenic substances cannot directly yield immune
    response, but need some help by some proteins)
    and then
  • They can react with antibodies.
  • All immunogens are antigenic but not all antigens
    are immunogenic

19
AntigenAntigen may be A) Complete
B) Incomplete
  • Properties of antigen( Foreign substances) to be
    Immunogenic
  • 1) Foreignness
  • A) Autologous antigens are self antigens and
    there will be no immune response.
  • B) Allogenic antigens are from the same species
    and there may be reaction, eg. Blood transfusion,
    kidney transplant.
  • C) Heterologous antigens are from different
    species
  • These antigens will be rejected and there will be
    severe immune response

20
  • Chemical-Structural complexity
  • A certain amount of chemical complexity is
    required eg aminoacid
  • Homoplymers are less immunogenic then
    heteropolymers containing
  • Two or three different aminoacids
  • Molecular Size
  • The most potent imunogens are proteins with high
    molecular weight
  • ie, above 100,000.
  • Generally, molecules with molecular weight below
    10,000 are weakly immunogenic, and very small
    ones eg an aminoacid are nonimmunogenic

21
Epitope
  • Epitopes are small chemical groups on the antigen
    molecule that can elicit and react with antibody
  • The antigen has variable number of epitopes and
    this is called the valency of the antigen

22
Hapten
  • Hapten is a greek word meaning to fasten. These
    are partial antigens. These are not immunogenic.
  • Hapten needs carrier proteins like albumin,
    globulin and synthetic polypeptide to become
    immunogenic.
  • Hapten (Hp)Carrier Protein (Cp) ?HpCp-?Ab
    formation against hapten
  • Antibiotics, analgesics, penicilin and
    alpha-methyldopa
  • Therefore haptens are antigenic and not
    immunogenic

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ADJUVANTS
  • Adjuvant word is from Latin means aidingand
    these are immunopotentiating agents.
  • These are of two types
  • ( AgAb)---?Injected----gtIncreased immune
    response

25
  • Today, adjuvants play an important role in
    the efficacy of vaccines. Stimulating the correct
    immune response is a must when selecting an
    adjuvant to use for a new vaccine. Since one
    adjuvant alone is rarely optimal for all
    antigens, it is critical to have a selection of
    different types of adjuvants for evaluation with
    your antigen.  MVP offers a selection of oil
    emulsion based adjuvants, polymer based adjuvants
    and co-polymer based adjuvants. 

26
Enhance the response to immunogens with Imject
Adjuvants.
  • Adjuvants are nonspecific stimulators of the
    immune response. When mixed with an antigen or
    immunogen, adjuvants help to deposit or sequester
    the injected material thereby helping to increase
    antibody response. Adjuvants enhance the immune
    response to compounds that are already
    immunogenic they do not confer immunogenicity to
    non-immunogenic haptens. To make prospective
    antigens more immunogenic, it is necessary to
    conjugate them to a carrier protein or some other
    complex, immunogenic molecule.

27
Thank you
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