4- Immunology- Pt 1A.docx

- **Infectious Disease: General Info** - Infectious disease requires a susceptible host and pathogen to both be in the same environment all at once. - The immune system works to prevent infection. - The **immune system** is a collection of cells, tissues, and...

- **Infectious Disease: General Info** - Infectious disease requires a susceptible host and pathogen to both be in the same environment all at once. - The immune system works to prevent infection. - The **immune system** is a collection of cells, tissues, and molecules that mediate resistance to foreign elements. - The **immune response** is coordinated reaction of these (immune) cells and molecules to antigens. - **Immunology** is the study of the immune system, including its responses to microbial pathogens and damaged tissues and its role in disease. - An **antigen** is a molecule that induces immune response when introduced into the body, - Antigens are what generate antibodies. - **Epitopes** **(or antigenic determinants)** are a part of an antigen that is actually responsible for inducing the immune response and binding to the products of the immune response (lymphocyte receptors and antibodies). - **Immune System: General Info** - The immune system must be able to discriminate foreign elements from components of its own organism. - If the immune system cannot distinguish between the 2, it will result in autoimmunity, which is when the body is attacking its own cells. - This can lead to auto-immune disorders/disease. - Immune responses should be generated only when components of the immune system come into contact with non-self-elements, such as antigens or microbes. - **Inflammation** causes pain, swelling, and redness. - The lack of cilia can predispose animals to diseases like chronic URI's (upper respiratory infections). - All cells of the immune system originate from hematopoietic cells, which come from bone marrow. - These **hematopoietic cells** differentiate into either common lymphoid progenitor or common myeloid progenitor. - **Common lymphoid progenitor** is the source of B-cells and T-cells, which are a part of adaptive immunity. - They also are the source of NK cells and ICL. - **Common myeloid progenitor** is the source of mast cells, basophils, dendritic cells, monocytes (macrophages), eosinophils, and neutrophils. - Cells of the immune system include: - Granulocytes: neutrophils, basophils, and eosinophils - Lymphocytes: NK cells (apart of innate immunity), T-cell and B-cells (apart of adaptive immunity) - Others: mast cells, monocytes/macrophages, and dendritic cells - Complement are mediators of inflammation, and elimination of microbes. - **Innate vs. Adaptive Immunity** - **Innate immunity** involves a non-specific immune response. - Examples include: inflammation, complement, and physical barriers (such as skin or stomach pH) - Innate immunity is always active, has a fast (minutes-hours) response time, and lacks memory. - The mains cells involved in innate immunity are: macrophages, neutrophils, and NK (natural killer) cells. - Innate immunity has specificity of structures common to several pathogens. - **Adaptive immunity** involves a specific immune response- meaning that only specific pathogens will be targeted. - Examples include: humoral immunity, and cellular immunity. - If there is no antigen, adaptive immunity will not illicit a response. - Adaptive immunity is only active when in contact with antigens, has a slow (days-weeks) response time, and has memory. - The main cells involved in adaptive immunity are T-cells and B-cells (which are lymphocytes). - B lymphocytes produce antibodies. - T cells fight microbes. - Adaptive immunity has a specific epitope, typically unique to a pathogen. - **Neutrophils** - Neutrophils have a segmented nucleus once they are fully mature, as well as granules in their cytoplasm, which are non-visible. - Neutrophils play the following roles: antimicrobial effectors, particularly in acute bacteria; infection/inflammation. - Neutrophils use the following mechanisms: phagocytosis, degranulation, neutrophil extracellular trap formation. - Degranulation involves the release of toxic granules which kills anything surrounding it. - The neutrophil extracellular trap involves pushing DNA out of cells, and using that DNA to capture and kill microbes. - This mechanism will kill the cell (in a form of cellular suicide). - **Eosinophils** - Eosinophils have a segmented nucleus, as well as granules in their cytoplasm, which are visibly pink/orange. - Eosinophils play the following roles: antiparasitic effector (particularly in helminthic infection), some antiviral action, and an allergy role. - They have a very good antiparasitic response. - Eosinophils use the following mechanisms: degranulation, and very limited phagocytosis (although eosinophils are not generally considered to be phagocytic). - **Basophils** - Basophils have a segmented nucleus, as well as granules in their cytoplasm, which are visibly purple (due to them being basophilic). - Basophils play a role in being a mediator of inflammation. - Basophils have the same mediators as mast cells but there are much less effective in comparison to mast cells. - Basophils use the mechanism of degranulation. - They are found in tissue, and not typically in blood. - **Mast Cells** - Mast cells have a segmented nucleus, as well as granules in their cytoplasm, which are visibly purple (due to them being basophilic). - Mast cells play the following roles: immune surveillance, mediator and amplifier of inflammation and allergy. - Mast cells use the following mechanisms: detection of threats and release of inflammatory mediators via degranulation (vasoactive amines) or synthesis of lipid mediators and cytokines. - The release of granules triggers inflammation. - The vasoactive amines induce vasodilation and increase vascular permeability. - They are not found in blood, but can be found in tissue and connective tissue. - **Macrophages** - Macrophages are monocytes that have left the blood and went to the tissue, and they are primarily considered to be a part of the innate immune response. - The primary functions of macrophages include: immune surveillance, moderate antimicrobial capacity, and limited antigen presentation. - Antigen presentation allows for the transitioning from innate to adaptive immune response. - Macrophages use the following mechanisms of action: detection of threats and release of inflammatory mediators, and phagocytosis. - Macrophages are considered to be the main type of phagocytic cell. - Macrophages can differentiate into dendritic cells. - **Dendritic Cells** - The primary functions of dendritic cells include: immune surveillance, and antigen processing and presentation. - The mechanisms of action for dendritic cells include: endocytosis, phagocytosis, and the detection of threats and release of inflammatory mediators. - Dendritic cells can sometimes be phagocytic, but their primary role is antigen presenting. - Dendritic cells work by capturing microbes, breaking them down, and presenting their antigens to T-cells, which initiates the adaptive immune response. - Dendritic cells are the only cells that can activate T-cells. - **NK (natural killer) Cells** - NK cells are lymphocytes that lack antigen receptors. - NK cells play the following role: destruction of virally infected or abnormal host cells (including tumor cells). - NK cells use the following mechanisms: recognition of virally infected or abnormal host cells and targeted release of cytotoxic granules. - NK cells are unique, in that they do not require activation prior to partaking in killings. - They induce apoptosis. - **Lymphocytes (T-cells and B-cells)** - T-cells and B-cells play the following roles within adaptive immunity: recognition of specific antigens/epitopes via TCR (T cell receptors) and BCR (B cell receptors). - T cells produce cytokines. - B cells produce antibodies. - T cells and B cells use the following mechanisms: activation and regulation of cell-mediated and antibody responses; memory cells - Each T cell and B cell have multiple receptors on their surface, but each cell will only have specificity to 1 thing. - **Immune System: Cell to Cell Communication** - **Receptors** are expressed on the surface of a cell or in intracellular compartments. - **Ligands** are molecules that activate receptors. - They can be soluble, or membrane bound. - The traveling of ligands to receptors can be time consuming, so cytokines can be used instead, for a faster response time. - **Cytokines** are proteins with functions of cell growth and activation. - Cytokines can differentiate into T-cells. - There are 2 types of cytokines: Interleukins and Chemokines. - Interleukins are used for communication between cells. - Chemokines are used for chemotaxis.