Immune Systeml a biochemical complex that protects the body against pathogenic organisms and other foreign bodies.l The structure, cells and soluble constituents that allow the host to recognize and respond to foreign stimulus.
Primary Role of The ImmuneSyateml Surveillance and destruction of substances that are foreign to the body.- bacteria, viruses, parasites or fungi
Primary Function of the Immune System1. To protect the body against invasion by so called non-self substance.(any and all substances that are considered “foreign”)2. To differentiate between “self” and “non- self” and to destroy that which is “non- self”
Origin, Destination and Structure of the Cells and Tissues
Bone Marrowq constitutes almost 5% of the total body weight and is responsible for the formation of all blood cells in adult
Stem Cellsq all cells originates from undifferentiated pluripotential hemopoietic stem cells, which can be found first in the mammalian embryo with in the liver then the spleen.q are pluripotential CD34+
l Erythropoiesis q occurs when a CFU-S cell gives rise to burst-forming units-erythrocytesl granulocytopoiesis q the generation of three types of granulocytesl monocytes q more pathogenic than neutrophils or eosinophils
Dendritic Cellsq are bone marrow derived cells specialized for presenting antigens to either CD4+ or CD8+ t cells in order to initiate a primary immune response.
Thymusq is a primary lymphoid organ that is required for the generation of immunocompetent CD3+4+ & CD3+8+ cells necessary for an adaptive immune response.
Lymph Nodesq are encapsulated structures that are strategically placed throughout the body to receive and filter antigens & cells from peripheral interstitial fluid and lymph.
Localization of Cells1.Superficial cortex q containing primary & secondary follicles with germinal centers containing dark and light zone2. Deep cortex q containing high endothelial post-capillary venules3. Medulla q with medullary cortex
Spleenl is an encapsulated organ with lymphoid tissue called white pulp(WP), which can respond to blood-borne antigens surrounded by the red pulp(RP).l Mucosal Associated Lymphoid Tissue (MALT)
T Cellsl about half of the stem cells migrates to the thymus gland where they differentiate into T lymphocytes or T cellsl small lymphocytes found in the bloodl about 70%-80% of the lymphocytes in peripheral blood are T cells.
Two immunologic Functions of T cells1. Effector q includes the cytolysis of virally infected cells & tumor targets & the production of lymphokines2. Regulator q includes the ability to amplify or suppress other effector lymphocytes
Most of the T-cells express three of the following CD Markersl CD2l CD3l CD4l CD8
Two Subpopulation of T cell in the Circulation1. Those with CD2, CD3, CD4 phenotype2. Those withCD2 ,CD3, CD8 phenotype
includes: 1. Helper T cells (Th cells) 2. Suppressor T cells ( Ts cells) 3. Cytotoxic T cells (Tc cells ) 4. Delayed hypersensitivity T cells (Td cells)
B cellsl Other lymphocytic stem cells differentiate in the liver & intestinal lymphoid areas into B lymphocytes or B cells.l About 10%-15% of the lymphocytes in peripheral blood are B cells.l Each is capable of producing hundreds of specific antibodies per second
IMMUNITYin positive sense: q providing natural resistance, recovery, and acquired resistance to infectious disease.in negative sense: q may result in rejection of a life-saving transplant
Types of Immunity
Natural or Innateq present at the time of birth or that develops during maturation
- refers to anatomical, cellular, and humoral defenses that function in the early stages of host defense response to foreign substances (antigens)- cells that function in innate immunity does not possess immunological memory.- they are nonspecific because the cells do not express receptors specific to one particular antigen.
Acquired or Adaptiveq which is acquired as a result of prior experience with a foreign substance
Further divided into:humoral immunity (gut associated tissue GALT) q is mediated by the antibody secreted by terminally differentiated B cells, the plasma cells q Type I, II, III hypersensitivity reactionsCell mediated immunity (Thymus) q involves T cells that recognize antigen in an MHC- restricted fashion (CD4 - T-helper cells, CD8 - T-suppressor cells) q tissue graft rejection, delayed hypersensitivity reaction, mononuclear inflammatory reaction
Characteristic of Natural Immunity1. Do not possess immunologic memory2. Non specific • operates as the first line of defense against pathogens includes the Physical barriers: – Skin – Mucous membrane – Susceptibility & nonsusceptibility – The provision of an unfavorable environment for the infecting organism
Other factors that forms theoverall action of innate immunity1. Inflammation2. Complement3. Phagocytosis
Adaptive immunity1. Acquired adaptive immunity q is highly specific, inducible, discriminating & unforgetting. - cell surface receptors are specific for a particular antigen. - memory because lymphocytes that have been activated in response to a particular antigen will respond much faster in a subsequent exposure to the same antigen. q T lymphocyte dependent response.
TwoTypes of Adaptive immunity1. Acquired active immunity q by actual infection or inoculation that causes the production of specific protective antibodies (vacines - hepatitis, tetanus)2. Acquired passive immunity q afford temporary protection against invading antigen. (RhIg given during birth, HBIg)
Characteristic of Adaptive Immunity1. With Memory2. Specific
Host Defense in Adaptive immunity1. Cells q B cells q plasma cells q T cells (cytotoxic & helper cells)2. Humoral factors q antibodies q cytokines
Factors involved in the degree of infectionl size of infecting dosel route of administrationl type of infective agent
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