IMMUNE RESPONSE
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Dr.T.V.Rao MD
Human Body is a Complex Structure
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Immune System Controls the Immune Responses
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Organs of Immunity Coordinate different functions
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Immunity is a less Understood Puzzle
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Path of Immune Response
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Immune Response Protects
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Immune Response A complex Mechanisms
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Several Cell Interaction compromises the Immune Response
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B Cells and T Cells work in Coordination
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Immune response works at Cellular level
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The Immune response
An immune response is what the immune system does when confronted by an antigen.
An immune response is an elaborate interplay between antigen, non-specific defenses, and B and T lymphocytes.
The process involves direct contact (cells, molecules bind to receptors on cell surfaces) and cytokines (messenger molecules) that also bind to receptors on cell surfaces.
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Results of Immune Response
Beneficial, Indifferent,
Injurious,
Reactions follow against any antigen either living or dead. May respond in
Specific or No reactivity or
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Tolerance.
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Classification of Immune Response
1 Humoral 2 Cell Mediated type May work together. May work in opposite way,
One may be more active than other.
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Immune Response Humoral / Cell Mediated
Active against Most Extra cellular Bacterial pathogens Viruses, Participates in Type 1 , 2, 3, Hypersensitivity reactions Auto Immune Disorders. Protects against, Fungus, Viruses IC bacterial infections Rejection of Homograft ,GVH, Immunological survelliance,cancer T cell mediated Hypersensitivity Auto Immune Disorders
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Structure of Immunoglobulin
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Humoral Immune Response
Produces Antibodies B Cell Plasma cell Antigen Presented to Immunocompetent cells Processed Secretion of Antibodies,
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Immune response is brought about by three types of cells 1 APC macrophages, and dendritic cells, 2 T Cell and 3 B cells The first step is capture and processing of antigens by APC and their presentation with the association of appropriate MHC molecule to T cells However some polysaccharides and simple molecules with repeating epitopes do not require T Cell participation
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Production of Antibodies
Stages of Antibody mediated immune response
Contain three stages 1 The entry of antigen, its distribution and fate in the tissues and its contact with appropriate immunocompetent cells 2 The secretion of antigen by cells and the control of the antibody forming process 3 The secretion of antibody its distribution in tissues and body fluids and manifestations of its effects.
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Pathogens damage tissue in a variety of ways
*e.g., LPS; a polyclonal B cell activator, Dr.T.V.Rao MD
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Pattern of Antibody production.
A Lag Phase A Log Phase raise of antibody levels, Plateau A phase of Decline.
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Primary and Secondary Immune Responses
A single injection of antigen helps in sensitizing or priming of immunocpompent cell producing particular antibody than in the actual elaboration of high levels of antibody. Effective levels of antibody are usually induced by only subsequent injection of antigens. Dr.T.V.Rao MD 26
Booster Dose
The antibody response to an initial antigenic stimuli differs qualitatively and quantitatively from response to subsequent stimuli with the same antigen The former primary response and later secondary response
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Primary and Secondary Response
The primary response is slow, sluggish and short lived with long lag phase and does not persist for long time The secondary response is prompt powerful and prolonged with short or negligible lag phase and with higher level of antibodies
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Types of Antibody Response,
Initial Antigenic Stimulus (Primary Response Ig M Response is slow and short lived, Secondary Response Ig G Response is Prompt ,Powerful and Prolonged Higher level of Antibodies and Lasts longer,
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How long a Antibody be active
The duration of the lag phase and persistence of the antibody dependent on the nature of the antigen In diphtheria toxoid the lag phase in the primary response may be long as 2 -3 weeks In pneumococcal polysaccharides antigens the antibodies are detected in few hours
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Priming and Booster doses
The first injection is known as priming dose and subsequent injection as booster dose. With live vaccines a single dose is sufficient a single dose is sufficient as multiplication of the organisms in the body provides a continuous antigenic stimulus that acts as both the priming and booster dose
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Fate of Antigens
Depends on the physical and chemical nature of antigens, dose and route of entry Whether induced primarily or secondarily The antigens introduced by IV are rapidly localized in the spleen, liver, bone marrow kidney and lungs Broken down by RES cells excreted in urine About 70 80 % Dr.T.V.Rao MD eliminated in one or two 32 days
Fate of Antigens
When antigens are introduced by subcutaneously are mainly localized in the draining lymph nodes only small amounts being found in the spleen The pariculate antigens are removed from circulation in two phase the first is antigens are engulfed by phagocytic cells broken down and
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Fate of Antigen
With the appearance of specific antibody the phase of immune elimination begins The antigen and antibody complexes are rapidly phagocytized results in disappearance of antigen from circulation Dr.T.V.Rao MD
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Immunoglobulin controlling genes and Generation of Diversity.
Genes control Antibody production and Diversity, V and C regions Kappa light chain / Lambda light chain Rearrangements produce enormous diversity variety of Immunoglobulin Combinations produce random selections.
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Immunoglobulin Switching.
Ig M specific for Antigen is produced. Switch to others Ig G - Ig A -Ig E But retain the same specificity, But carry different Biological activities
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Relation of Dose and Nature of Antigen to Antibody production.
Single Dose Sensitizing. Subsequent Dose More effective. Non Living Vaccines multiple doses. Living Vaccines one Dose is productive. Fate of Antigen I V eliminate faster, in 2-3 days, in spleen. SC Lymph nodes Little in spleen Engulfed by Phagocytes Broken Down and eliminated.
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Fate of Antigen in the Host
Ag+Ab from complexes and Phagocytes will engulf and Disappear -- Immune Elimination. Immune Complexes can cause damage. Proteins eliminated in 1-2 weeks, Polysaccharides months to years. Pneumococcal polysaccharides up to 20 years.
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Production of Antibodies.
Immune Responses to Antigen, Antigen Presenting Cells APC Macrophages Dendritic Cells T and B Lymphocytes, Capture by APC ( Proteins RBC ) T Cell take active part. T Cell Independent - Polysaccharides.
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Production of Antibodies needs help and coordination with other structures CD4 Helper cells MHC II CD8 Cytotoxic cells MHC TH cells require two signals IL1 Next produce IL2 Produce cytokines IL4 IL5 IL6 B cells stimulated Produce antibody producing plasma cells produced
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Factors Influencing Antibody production
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Factors Influencing Antibody Production
Under genetic control, May be responder or Non responder.- defines the capacity of the individual to respond or not respond Ir (Immune response genes) control this property. Age The embryos is immunologic ally immature During the embryonic life the developing lymphoid cells come into contact with all the tissue antigens of the body released by cellular breakdown lead to elimination of self antigens
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Immunity in Neonates
Early mechanisms of self tolerance. -> 3-6 months Maternal antibodies, Ig G 5-7 years Ig A 10-15 years B cell responses to most proteins and other T cells dependent develop early. The responses to Polysaccharide and other T cell independent antigens develop later.
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Humoral Immunity in vivo uses
Immunoglobulin IgA can stop colonization of mucosal surface. It interferes with the attachment molecular adhesions present on the bacterial surface. Bacterial exotoxins are inhibited as the antibodies can prevent interaction of enzymes with substrate.
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Humoral immunity in vivo uses
Antibodies can kill bacteria. Antibodies can affect the specific transport systems and deprive the energy needs of the bacteria. Affect the motility Reduces the invasion Antibodies can cause agglutination Stimulate the phagocytosis, and complement activity.
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Other Factors influencing the Antibody production
Nutrition Malnutrition Humoral reduced, CMI reduced Route of administration Large particles increased. Application to skin CMI Deltoid more effective
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Other factors,
Size and Dose has relation Massive Dose paralysis. Anamnestic reaction Administration of Multiple antigens Triple antigen, Freunds Adjuvant. Increases with Tubercle Bacilli
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Uses of Administration of Antibodies
Passive administration of Antibodies eg Hyper immune globulins, Sensitization issues in Rh negative mothers. The effect occurs due to feedback mechanism The antibody may also combine with antigen and prevent its availability for the immunocompetent cells. Rh ve mother + Rh+ ve fetus Administration of Anti-Rh globulin immediately following delivery
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Administration of Immunoglobulin's
IV administration has immunomodulation effect Administered in
Thrombocytopenia's,
and autoimmune hemolytic anemia.
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Adjuvants
Defined as substance that enhances the immunogenicity of an antigen. Eg Aluminum hydroxide or phosphate Freunds incomplete adjuvant Incorporation of protein antigen in water phase of water in oil emulsion, it causes delay of release of antigen from the site of injection and prolong the antigenic stimulus. Freunds complete adjuvant contains also the suspension of killed tubercle bacilli. The effect is due to MDP ( muramyl dipeptide )
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Super antigens,
Protein Molecules, eg Staphylococcal Enterotoxin, Activate large number of T cells, Irrespective of Antigenic specificity, Usually few cells are stimulated ( 0.001%) Massive stimulation leads to Massive out porins of T cell cytokines, Multi organ Dysfunction Staphylococcal Shock syndrome
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Super antigens,
Protein Molecules, Eg Staphylococcal Enterotoxin, Activate large number of T cells, Irrespective of Antigenic specificity, Usually few cells are stimulated ( 0.001%) Massive stimulation leads to Massive out pouring of T cell cytokines, Multi organ Dysfunction Staphylococcal Shock syndrome
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Immunosuppressive Agents
X rays, Corticosteroids Anti metabolites. Cytotoxic
Chemicals
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Superatigens stimulates several lymphocytes
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Monoclonal Antibodies
Kohler and Milstein ( Nobel Prize 1984 ) A single antibody forming cell or clone produces Antibodies against single antigen, Antibodies are usually polyclonal, Clone of Lymphocytes Monoclonal antibodies. Useful in Diagnostic / Research work.
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How Hybridoma Created.
Immunize Mice with Antigen, Obtain spleen cells Fuse with Mouse Myeloma cells Grow then in HPRT medium Hypoxanthine,Phosphorib osyl transfeerase Transfer to HAT Medium ) Hypoxanthine, Aminoptren and Thymidine Medium } Lead to formation of Dr.T.V.Rao MD Hybridoma.
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Hybridoma Technology Produce Monoclonal Antibodies
What is Hybridoma Fusion of Spleen cells + Myeloma Cells, Attains the capacity to produce 1. Antibody producing capacity. 2. Multiply indefinitely,
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Contents of Hybridoma
Splenic cells + Myeloma cells Produce Monoclonal Antibodies, Propagated by injecting intraperitoneally In Mice Frozen Monoclonal are similar in Ig class and other characters.
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Uses of Monoclonal Antibodies
1 Research applications, 2. Diagnostic. 3.Theraputic, Mice Monoclonal are suitable for Humans, Chimeras antibodies are created. Grafting of Murine Monoclonal on CDR loops. Antibodies can be used with Bacteriophages Dr.T.V.Rao MD 62 Advances in Immunotherapy.
Immune Response in Cell mediated Immunity CMI
T Lymphocytes play the major role
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CMI helps in
Delayed hypersensitivity Immunity in infections caused by Obligate and facultative intracellular parasites Eg Tuberculosis, Leprosy Listeriosis, Brucellosis, Fungi Histoplasmosis,
Cocccidiomysosis,Blastomycosis, Parasites Trypanosomiasis In transplantation immunity, Immunologioly in Transplantation, malignancy, Pathogenesis of Autoimmune diseases
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Induction of Cell Mediated Immunity
Depends on Nature of Antigenic stimulus Best developed after following infection with intracellular parasites Live vaccines highly stimulating Killed vaccine not very effective But effective if contains Freund type adjuvant.
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Functions of T cells
Only T cell dependent antigens lead to development of CMI Certain chemicals which come in contact with skin induces Delayed hypersensitivity T Cell contain the specific receptor ( TCR ) One epitope ( Antigen ) on contact with receptor undergoes blast transformation Leads to Clonal proliferation
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Functions of T cells
Cytotoxic T cells recognize antigen on surface of virus infected cells, tumor cells, allograft cells with MHC I and sectored Lymhokines and destroy target cells MD Dr.T.V.Rao
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Functions of T cells
The stimulated cells undergoes blast transformation, Clonal proliferation Leads to Effectors cells and Memory cells T cell react on presentation with MHC Helper T cells when presented on surface of macrophages or other cells complexes with MHC II molecule leads to release of Biological Mediators Lymhokines activate Macrophages and kills intracellular parasites
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Broad view on Cytokines Cytokines are a category of signalling proteins and glycoproteins that, like hormones and neurotransmitters, are used extensively in cellular communication
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Cytokines
Cytokines have been classed as Lymhokines, interleukins, and chemokine's, based on their presumed function, cell of secretion, or target of action. Because cytokines are characterised by considerable redundancy and pleiotropism, such distinctions, allowing for exceptions, are obsolete.
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Definitions
Lymhokines Biologically active substance released by activated T Lymphocytes
Monokines Substances secreted by
Monocytes and Macrophages Interleukins Produces by lymphocytes which exert a regulatory effect on other cells
All above grouped under cytokines
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Definitions
Autocrine, if the cytokine acts on the cell that secretes it. Paracrine, if the target is restricted to the immediate vicinity of a cytokine's secretion. Endocrine, if the cytokine diffuses to distant regions of the body (carried by blood or plasma). It seems to be a paradox that cytokines binding to antibodies have a stronger immune effect than the cytokine alone. This may lead to lower therapeutic doses.
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What are Cytokines
They are peptide mediators, intracellular messengers, which regulate immunological, inflammatory and reparative host cell responses They are potent hormones Active even at Fetomolar concentrations produced by widely distributed cells ( Lymphocytes, Macrophages, Platelets, and Fibroblasts.
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Cytokines
Cytokines may act on the cells that secrete them (Autocrine action), on nearby cells (paracrine action), or in some instances on distant cells (endocrine action)
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Cytokines have
Paracrine effect acts locally near the producing cells Having pleotrophic effects Multiple effects on growth and differentiation of various cell types.
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Important Cytokines
Interleukin I 1979 Interleukin I divided into Alpha and Beta IL1 is secreted by Macrophages, Monocytes other nucleated cells. Stimulated by Antigens, Toxins, Injury, Inflammation, Inhibited by
Cyclosporins,Corticosteiods,Prostaglandins
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Functions of Interleukin 1
IL1 stimulates T cells and Produces IL2 and other Lymhokines Helps B cell proliferation Synthesizes Antibodies Helps Neutrophils in Chemo taxis Promotes Phagocytosis Promotes Metabolic Physiological and inflammatory responses by action on Bone marrow
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IL1 initiates Fever
IL1 is crucial in promoting fever and called as Pyrogens. With the help of Tumor Necrosis factor causes hematological changes in Septicemias, Shock and bacterial meningitis
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Other Interleukins
Interleukins 2 Modulates the immune response Major activator of T and B Lymphocytes Stimulates cytotoxic T cells and Natural Killer cells. Interleukin 3 Stimulates multilineage cells of the Hematopoietic system.
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Other Interleukins
Interleukin 4 Acts as a Growth factor for T Lymphocytes Interleukin 5 Causes the proliferation of activated B Lymphocytes Interleukin 6 Produced by Stimulated B and T Lymphocytes Induces the production of Immunoglobulin synthesis Stimulates the Hepatocytes, nerve cells,Hematopoetic cells
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Theraputic Uses of Cytokines
IL1,2,3 and colony stimulating factors are used in
Inflammatory diseases, Infections, Autoimmune diseases.
Neoplastic diseases and
cancers
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Mechanisms in Inflammatory Response
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Mechanisms in Inflammatory Response
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Functions of Cytokines
Autocrine, if the cytokine acts on the cell that secretes it. Paracrine, if the target is restricted to the immediate vicinity of a cytokine's secretion. Endocrine, if the cytokine diffuses to distant regions of the body (carried by blood or plasma). It seems to be a paradox that cytokines binding to antibodies have a stronger immune effect than the cytokine alone. This may lead to lower therapeutic doses.
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Properties of Cytokines
Cytokines are small secreted proteins which mediate and regulate immunity, inflammation, and hematopoiesis. They must be produced de novo in response to an immune stimulus. They generally (although not always) act over short distances and short time spans and at very low concentration.
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Properties of Cytokines
They act by binding to specific membrane receptors, which then signal the cell via second messengers, often tyrosine kinases, to alter its behaviour (gene expression). Responses to cytokines include increasing or decreasing expression of membrane proteins (including cytokine receptors), proliferation, and secretion of effector molecules.
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Properties of Cytokines
Cytokine is a general name; other names include lymphokine (cytokines made by lymphocytes), monokine (cytokines made by monocytes), chemokine (cytokines with chemotactic activities), and interleukin (cytokines made by one leukocyte and acting on other leukocytes).
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Properties of Cytokines
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Other Cytokines
Other groups of cytokines include interferons and chemokine's. Interferons IFNa and IFNb inhibit virus replication in infected cells, while IFNg also stimulates antigen-presenting cell MHC expression. Chemokine's attract leukocytes to infection sites. Chemokine's have conserved cysteine residues that allow them to be assigned to four groups.
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Inhibitory Cytokines
Some cytokines are predominantly inhibitory. For example, IL-10 and IL-13 inhibit inflammatory cytokine production by macrophages.
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INTERFERONS
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Interferons
Primarily identified as Antiviral agents Now classified as Cytokines Interferons play an important role in the first line of defence against viral infections. They are part of the non-specific immune system and are induced at an early stage in viral infection before the specific immune system has had time to respond..
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Dynamics of Interferons
Interferons are made by cells in response to an appropriate stimulus, and are released into the surrounding medium; they then bind to receptors on target cells and induce transcription of approximately 20-30 genes in the target cells, and this results in an anti-viral state in the target cells.
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Classification of Interferons
There are three classes of Interferons: Alpha, Beta and Gamma. Interferon Alpha and Beta are produced by many cell types
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Types of Interferons
Interferon-alpha (leukocyte interferon) is produced by virus-infected leukocytes, etc Interferon-beta (fibroblast interferon) is produced by virus-infected fibroblasts, or virus-infected epithelial cells, etc Interferon-gamma (immune interferon) is produced by certain activated T-cells and NK cells. Interferon-gamma is made in response to antigen (including viral antigens) or mitogen stimulation of lymphocytes.
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Functions of Interferons
Interferons are within the cytokine family of proteins. Interferons are especially important because they enhance the immune systems ability to recognize foreign invaders, enabling the system as a whole to function more effectively
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Interferons Gama
Interferon-Gamma is involved in the regulation of immune response throughout the body. Interferon-Gamma is the signalling protein that gets the immune system as a whole ready for attack and fine tunes it to quickly and effectively get rid of foreign and unwanted intruders
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Uses of Interferons
Interferons-alpha and -beta have been used to treat various viral infections. One currently approved use for various types of interferon-a is in the treatment of certain cases of acute and chronic hepatitis C and chronic hepatitis B.
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Uses of Interferons
Interferon-gamma has been used to treat a variety of disease in which macrophage activation might play an important role in recovery, eg. lepromatous leprosy, leishmaniasis, toxoplasmosis. Since interferons have anti-proliferative effects, they have also been used to treat certain tumours such as melanoma and Kaposis sarcoma.
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Detection of CMI
The basic and earlier test was skin test for delayed hypersensitivity Now other tests are available Lymphocyte transformation test Migration inhibiting factor test.
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Theories of Immune Response
Several theories are considered 1 Direct template theory 2 Indirect template theory 3 Natural selection theory 4 Clonal selection theory
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What is Clonal Selection Theory
Burnet proposed the theory 1957 The theory emphasizes the immunological specificity to cellular level In this theory the cell are formed by somatic mutation, the cells that react with self antigens are eliminated and called as Forbidden clones. Their persistence in later life leads to Autoimmune process
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Jernes network hypothesis
It explains the mechanism of antibody response The variable region of an immunoglobulin molecule carrying the antigen combining site is different in different antibodies The distinct Aminoacid sequence at antigen combing site and the adjacent parts of the variable regions are termed as idiotype Produce antiidotypic antibodies Which in turn produce antibodies to them
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Nobel Prize winning theory
Which in turn produce antibodies to them Forms a idiotype network The above process controls the amount of antibodies The above theory by Niels K.Jerne was awarded Nobel Prize Dr.T.V.Rao MD for Medicine in 1984
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Recent Theories
Now genetic basis of antibody diversity is identified. The recent theory of Split genes explains many unknown mechanisms The theory says the information occurs in discontinuous stretches of DNA, each coding for separate regions of the antibody molecule
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