Download Lecture outline : Immunity This is a protective or defense mechanism

Lecture outline :
Immunity
This is a protective or defense mechanism of our body, which leads us to a healthy
life.
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
Important components of innate immunity
(Factors that limit entry of microorganisms into the body)
-Keratin layer of intact skin
- Lysozyme in tears and other secretions
- Low pH in stomach and vagina fatty acids in skin
- Surface phagocytes (eg. alveolar macrophages)
- Defensins (cationic peptides)
- Normal flora of throat, colon and vagina
Important components of innate immunity
(Factors 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)
Humoral
Immunity
Cell mediated
Immunity
Innate
Complement
Neutrophil
Macrophages
Natural killer cells
Acquired
B cells
Antibodies
Helper Tcells
Cytotoxic T cells
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
Major Functions Of T Cells and B cells
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)
Antibody-Mediated Immunity (B Cells)
1) Host defense against infection
2) Opsonize bacteria, neutralize toxins and viruses
3) Allergy (hypersensitivity) eg, hay fever anaphylactic shock
4) Autoimmunity
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)
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.
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
Immunogen and Antigen
•
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
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
2)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
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
Hapten
• Hapten is a greek word meaning to fasten. These are partial antigens. These are
not immunogenic.
• Hapten needs carrier proteins like albumin, gobulin and synthetic polypeptide to
become immunogenic.
• Hapten (Hp)+Carrier Protein (Cp) Hp+Cp-Ab formation against hapten
• Antibiotics, analgesics, penicilin and alpha-methyldopa
• Therefore haptens are antigenic and not immunogenic
ADJUVANTS
• Adjuvant word is from Latin means “aiding”and these are immunoptentiating
agents.
• These are of two types
• ( Ag+Ab)---Injected---->Increased immune response
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.
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 nonimmunogenic haptens. To make prospective antigens more immunogenic, it is necessary
to conjugate them to a carrier protein or some other complex, immunogenic molecule.
Learning Objectives

Immunity and its types

Components of innate immunity

Mechanism of immunity offered by B and T cells

Active , passive and Passive-Active immunity

Immunogen ,Antigen and the difference between them

Properties of antigens

Epitopes , haptens and adjuvants