What Happens When An Enemy Invades Your Body?
- THE IMMUNE SYSTEM
- The purpose of the Immune System is defense and protection through a system of surveillance
- This surveillance operates on the simple principal of distinguishing "self" from "non-self"
- The purpose of the Immune System is defense and protection through a system of surveillance
Outline Contents:
Effectors of the Immune System
Histocompatibility Genes
Immune Mechanisms
Autoimmune Disorders
Immunodeficiency Diseases
- EFFECTORS OF THE IMMUNE SYSTEM
- Cells & Cytokins
- T Lymphocytes
- B Lymphocytes
- Macrophages
- Dendrtitic & Langerhans Cells
- Natural Killer Cells
- Cells & Cytokins
- T Lymphocytes
- In the blood, T cells constitute 60 to 70% of peripheral lymphocytes
- In the blood, T cells constitute 60 to 70% of peripheral lymphocytes
- B Lymphocytes
- B lymphocytes constitute 10 to 20% of the circulating peripheral lymphocyte population
- B lymphocytes constitute 10 to 20% of the circulating peripheral lymphocyte population
- MACROPHAGES
- Macrophages play a major role in inflammation, but also have many activities in the immune response. (s28)
- Macrophages play a major role in inflammation, but also have many activities in the immune response. (s28)
- Dendric & Langerhan's Cells
- Dendritic cells are widely distributed. They are found in lymphoid tissue and in the interstitium of many nonlymphoid organs, such as the heart and lungs. Similar cells within the epidermis have been called Langerhans' cells (S31)
- Dendritic cells are widely distributed. They are found in lymphoid tissue and in the interstitium of many nonlymphoid organs, such as the heart and lungs. Similar cells within the epidermis have been called Langerhans' cells (S31)
- Natural Killer (NK) Cells
- Approximately 10 to 15% of the peripheral blood lymphocytes do not bear TCR or cell-surface immunoglobulins.
- Approximately 10 to 15% of the peripheral blood lymphocytes do not bear TCR or cell-surface immunoglobulins.
- HISTOCOMPATIBILITY GENES /Molecules
- Originally identified as antigens that evoke rejection of transplanted organs, histocompatibility molecules are now extremely important for the induction and regulation of the immune response and for certain nonimmunologic functions (s39)
- Originally identified as antigens that evoke rejection of transplanted organs, histocompatibility molecules are now extremely important for the induction and regulation of the immune response and for certain nonimmunologic functions (s39)
- Cytokines
- The induction and regulation of the multiple immune responses involve multiple interactions among lymphocytes, monocytes, inflammatory cells (neutrophils) and endothelial cells.
- The induction and regulation of the multiple immune responses involve multiple interactions among lymphocytes, monocytes, inflammatory cells (neutrophils) and endothelial cells.
- IMMUNE MECHANISM
(S66)
- Contact with antigen leads not only to induction of a protective immune response, but also to reactions that can be damaging to tissues
- An antigen is a substance that can be specifically recognized by the immune system and cause a response
- Contact with antigen leads not only to induction of a protective immune response, but also to reactions that can be damaging to tissues
- Tissue Damage (Hypersenstivity) (s76)
- Tissue-damaging immune reactions may be evoked not only by exogenous antigens, but also by those that are intrinsic to the body (endogenous) (s76)
- Tissue-damaging immune reactions may be evoked not only by exogenous antigens, but also by those that are intrinsic to the body (endogenous) (s76)
- Type I Hypersensitivity (Anaphylactic Type)
- A rapidly developing immunologic reaction occurring within minutes after the combination of an antigen with antibody bound to mast cells or basophils in individuals previously sensitized to the antigen.
- A rapidly developing immunologic reaction occurring within minutes after the combination of an antigen with antibody bound to mast cells or basophils in individuals previously sensitized to the antigen.
- Type II Hypersensitivity (Antibody Dependent)
- This type is mediated by antibodies directed toward antigens present on the surface of cells or other tissue components.
- This type is mediated by antibodies directed toward antigens present on the surface of cells or other tissue components.
- Complement-Dependent Reactions
- #1 – Antibody (IgM or IgG) reacts with an antigen present on the surface of the cell, causing activation of the complement system and resulting in the assembly of the membrane attack complex that disrupts membrane integrity by "drilling holes" through the lipid bilayer (s100)
- #2 – Cells become susceptible to phagocytosis by fixation of antibody or C3b fragment to the cell surface (opsonization). (s101)
- #1 – Antibody (IgM or IgG) reacts with an antigen present on the surface of the cell, causing activation of the complement system and resulting in the assembly of the membrane attack complex that disrupts membrane integrity by "drilling holes" through the lipid bilayer (s100)
- Antibody-Dependent Cell-Mediated Cytotoxicity
- This form of antibody-mediated cell injury does not involve fixation of complement but instead requires the cooperation of leukocytes.
- This form of antibody-mediated cell injury does not involve fixation of complement but instead requires the cooperation of leukocytes.
- Antibody-Mediated Cellular Dysfunction
- In some cases, antibodies directed against cell surface receptors impair or dysregulate function without causing cell injury or inflammation. (s107)
- In some cases, antibodies directed against cell surface receptors impair or dysregulate function without causing cell injury or inflammation. (s107)
- Graves' disease
- Graves' disease is the most common cause of hyperthyroidism
- Graves' disease is the most common cause of hyperthyroidism
- Type III Hypersensitivity (Immune Complex–mediated)
- These reaction are induced by antigen-antibody complexes that produce tissue damage as a result of their capacity to activate a variety of serum mediators, principally the complement system. (s114)
- These reaction are induced by antigen-antibody complexes that produce tissue damage as a result of their capacity to activate a variety of serum mediators, principally the complement system. (s114)
- Local Immune Complex Disease (Arthus Reaction)
- The Arthus reaction is a localized area of tissue necrosis resulting from acute immune complex vasculitis, usually elicited in the skin 128
- The Arthus reaction is a localized area of tissue necrosis resulting from acute immune complex vasculitis, usually elicited in the skin 128
- Type IV Hypersensitivity (Cell-Mediated)
- This type of hypersensitivity is initiated by specifically sensitized T lymphocytes, rather than by antibodies
- This type of hypersensitivity is initiated by specifically sensitized T lymphocytes, rather than by antibodies
- Summary of Immune Mechanisms
- Graft-versus-Host (GVH) Disease
- GVH disease occurs when immunologically competent cells are transplanted into immunologically crippled recipients. GVH disease occurs most commonly in the setting of allogeneic bone marrow transplantation but may also follow transplantation of solid organs rich in lymphoid cells (e.g., the liver) or following transfusion of unirradiated blood 139
- GVH disease occurs when immunologically competent cells are transplanted into immunologically crippled recipients. GVH disease occurs most commonly in the setting of allogeneic bone marrow transplantation but may also follow transplantation of solid organs rich in lymphoid cells (e.g., the liver) or following transfusion of unirradiated blood 139
- AUTOIMMUNE DISEASES
- Three requirements for autoimmunity:
- Three requirements for autoimmunity:
- Immunologic Tolerance
- Immunologic tolerance is a state in which the individual is incapable of developing an immune response to a specific antigen
- Immunologic tolerance is a state in which the individual is incapable of developing an immune response to a specific antigen
- Clonal Deletion
- This refers to loss of self-reactive T and B lymphocytes during their maturation
- This refers to loss of self-reactive T and B lymphocytes during their maturation
- Clonal Anergy
- This refers to prolonged or irreversible functional inactivation of lymphocytes, induced by encounter with antigens under certain conditions 144
- This refers to prolonged or irreversible functional inactivation of lymphocytes, induced by encounter with antigens under certain conditions 144
- Peripheral suppression by T cells
- Many factors, both cellular and humoral, that can actively suppress autoreactive lymphocytes have been described.
- Many factors, both cellular and humoral, that can actively suppress autoreactive lymphocytes have been described.
- Mechanisms of Autoimmune Diseases
- The pathogenesis of autoimmunity appears to involve immunologic, genetic, and viral factors interacting through complicated mechanisms that are poorly understood 147
- The pathogenesis of autoimmunity appears to involve immunologic, genetic, and viral factors interacting through complicated mechanisms that are poorly understood 147
- Bypass of Helper T Cell Tolerance
- Tolerance may be broken if the need for helper T cells is bypassed
- Tolerance may be broken if the need for helper T cells is bypassed
- Molecular Mimicry
- Several infectious agents cross-react with human tissues through their haptenic determinants (B-cell epitopes)
- Several infectious agents cross-react with human tissues through their haptenic determinants (B-cell epitopes)
- Polyclonal Lymphocyte Activation
- Autoimmunity may occur if such self-reactive but anergic clones are stimulated by antigen-independent mechanisms 151
- Autoimmunity may occur if such self-reactive but anergic clones are stimulated by antigen-independent mechanisms 151
- Imbalance of Suppressor-Helper T-Cell Function
- Any loss of suppressor T-cell function will contribute to autoimmunity, and, conversely, excessive T-cell help may drive B cells to extremely high levels of autoantibody production 152
- Any loss of suppressor T-cell function will contribute to autoimmunity, and, conversely, excessive T-cell help may drive B cells to extremely high levels of autoantibody production 152
- Emergence of a Sequestered Antigen
- Any self-antigen that is completely sequestered during development is likely to be viewed as foreign if introduced into the circulation, and an immune response will develop.
- Any self-antigen that is completely sequestered during development is likely to be viewed as foreign if introduced into the circulation, and an immune response will develop.
- Consequences of the loss of self-tolerance: autoimmune diseases
- Autoimmune diseases range from those in which the target is a single tissue, such as the autoimmune hemolytic anemias and thyroiditis, to those in which a host of self-antigens evoke a constellation of reactions against many organs and systems 154
- Autoimmune diseases range from those in which the target is a single tissue, such as the autoimmune hemolytic anemias and thyroiditis, to those in which a host of self-antigens evoke a constellation of reactions against many organs and systems 154
- Systemic Lupus Erythematosus (SLE) 155
- SLE is the a multisystem disease of autoimmune origin, characterized by a many autoantibodies, particularly antinuclear antibodies (ANAs).
- SLE is the a multisystem disease of autoimmune origin, characterized by a many autoantibodies, particularly antinuclear antibodies (ANAs).
- Sjögren's Syndrome
- Sjögren's syndrome is characterized by dry eyes (keratoconjunctivitis sicca) and dry mouth (xerostomia) resulting from immunologically mediated destruction of the lacrimal and salivary glands. 159
- Sjögren's syndrome is characterized by dry eyes (keratoconjunctivitis sicca) and dry mouth (xerostomia) resulting from immunologically mediated destruction of the lacrimal and salivary glands. 159
- Systemic Sclerosis (Scleroderma)
- Characterized by excessive fibrosis throughout the body. The skin is most commonly affected, but the gastrointestinal tract, kidneys, heart, muscles, and lungs also are frequently involved 162
- Characterized by excessive fibrosis throughout the body. The skin is most commonly affected, but the gastrointestinal tract, kidneys, heart, muscles, and lungs also are frequently involved 162
- IMMUNOLOGIC DEFICIENCY SYNDROMES
- Traditionally, immunodeficiency disorders are considered according to the primary component or components involved (i.e., the B cell, the T cell, the undifferentiated stem cell, or complement); however, in view of the extensive cell interactions between T and B lymphocytes and macrophages, these distinctions are not always clear-cut 167
- Traditionally, immunodeficiency disorders are considered according to the primary component or components involved (i.e., the B cell, the T cell, the undifferentiated stem cell, or complement); however, in view of the extensive cell interactions between T and B lymphocytes and macrophages, these distinctions are not always clear-cut 167
- Expansion of Immunologic Deficiency Syndromes
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