Immune System Flashcards
Innate Immunity (Nonspecific)
Composed of defenses that are always active against infection but lack the ability to target specific invaders over others
Adaptive Immunity (Specific)
Defenses that target a specific pathogen; Slower to act
Maintain immunological memory of an infection to mount faster subsequent attacks
Bone Marrow
Site of immune cell production; Produces all of the leukocytes (WBCs) through Hematopoiesis
Spleen
- Location of blood storage
- Filters blood and lymph
- Site where immune responses can be mounted (activation of B-cells) which turn into plasma cells to produce antibodies as part of adaptive immunity
Thymus
Small gland in front of pericardium where T cells mature (agents of cell mediated immunity); Coordinate the immune system and kill virally infected cells directly
Lymph Nodes
- Provide a place for immune cells to communicate and mount an attack
- Filter lymph fluid containing WBCs that drains through the lymphatic system into the blood stream
Gut Associated Lumphoid Tissues (GALT)
Immune tissue in close proximity to the digestive system including
- Tonsils
- Adenoids (head)
- Peyers patches (small intestine)
- Lymphoid aggregates in the appendix
Leukocytes
Come from Hematopoietic stem cells; Includes:
- Granulocytes:
- Neutrophils
- Eosinophils
- Basophils - Agranulocytes:
- Lymphocytes
- Monocytes
- Macrophages
Granulocytes
Cells have tiny granules in their interiors and participate in the inflammatory response; Includes Neutrophils, Eosinophils and Basophils
Agranulocytes
Includes Lymphocytes, Monocytes and Macrophages
Lymphocytes
Responsible for antibody production, immune system modulation and targeted killing of infected cells
Monocytes
Phagocytic cells in the blood stream
Macrophages
- Agranulocyte (monocyte) cell that reside within tissue; Engulfs and consumes pathogens
- Antigen on cell surface signals that the cell is infected and begins brings cytotoxic T-Lymphocytes to kill the intracellular pathogen and prevent the infection of other cells
Integument (Skin)
First line of defense and physical barrier - Excludes most bacteria, viruses, fungi and parasites; Sweat has antimicrobial properties
Defensins
Antibacterial enzymes present on the skin
Respiratory System
Line with mucous membranes and cilia to trap particulate matter and prevent bacteria / viruses from gaining access to deep lung tissue
Lysozyme
Nonspecific bacterial enzyme that is secreted in tears and saliva
Gastrointestinal System
Stomach secretes acid that kills most pathogens; The gut is also colonized by good bacteria
Complement System
Consists of a number of proteins in the blood tat act as a nonspecific defense against bacteria
Classical Pathway in Complement System
Binding antibody to pathogen
Alternative Pathway in Complement System
No Antibody - Proteins punch holes in cell walls of bacteria making them osmotically unstable
Inerferons
Proteins that prevent viral replication / dispersion cause nearby cells to decrease production of viral and cellular proteins and increase antigen presentation for better detection of infected cells by immune system
When A Bacterial Invader Enters a Tissue Macrophage
Endogenous Pathways (bind to the antigen from the inside of the cell:
- Phagocytize the invader through endocytosis
- Digest the invader using enzymes
- Present little pieces of the invader (as peptides) to other cells using Major Histocompatability Complex Protein (MHC)
- MHC Binds to pathogenic peptide (antigen) and carries it to the cell surface
- Macrophage releases Cytokines
Cytokines
Chemical substance that stimulates inflammation and recruits immune cells to the area
Major Histocompatability Complex Protein II (MHCII)
Exogenous Pathway: Antigen originated outside the cell
- Displayed by professional antigen presenting cells like macrophages; These phagocytic cells pick up pathogens from the environment and process them and then present them as an MHCII Antigen
Pattern Recognition Receptors (PRP)
Special Receptors found on macrophages and dendritic cells that recognize categories of invaders (bacterium, virus, fungus or parasite) allowing for production of appropriate cytokines to recruit immune cells and target particular groups of pathogens
Natural Killer Cells (NK)
Type of nonspecific lymphocyte able to detect down regulation of MHC and induce apoptosis in virally infected cells; Also goes after cancer cells
Dendritic Cells
Presents antigens, fragments of proteins or other molecules from the pathogens (or cancer cells) to adaptive immune cells; inducing the cells to attack those cells with displayed antigens
Mast Cell
Releases histamine and other chemicals in response to allergens to promote inflammation
- Exist in tissues, mucousa and epithelium
Neutrophil
Granulocyte; Phagocytic leukocyte in blood that target bacteria
- Use chemotaxis
- Opsonized bacteria (marked with antibody)
- Responsible for Pus
Chemotaxis
Sense certain products given off by bacteria and migrate with them to follow it back to the source
Opsonized
Bacteria will be opsonized; marked with an antibody from a B-cell that helps other cells to detect it
Pus
Collection of dead Neutrophils during infection
Eosinophil
Granulocyte; Contain bright red-orange granules primarily involved in allergic reactions and invasive parasitic infections
- Histamine
- Inflammation
Histamine
Release an inflammatory mediator for vasodilation and increased leakiness of blood vessels to allow additional immune cells to move from blood to tissue
Inflammation
Useful against Extracellular Pathogens including bacteria, fungi and parasites
Basophils
Contain large purple granules; involved in allergic responeses
- Mast cells
Humoral Immunity
Involves the production of antibodies that are specific to antigens of the invading microbes. They are produced by B-cells which are lymphocytes that originate and mature in bone marrow and are activated in the spleen and lymph nodes
Antibodies (Immunoglobulins - Ig) In Body Fluids
- Opsonization: Bind to specific antigen to attract other leukocytes to phagocytize those antigens immediately
- Can cause pathogens to clump together (aggregate) forming large insoluble complexes that can be phatgocytized
- Block the ability of a pathogen to invade tissue; Neutralizing it
Antibodies (Immunoglobulins - Ig) On Cell Surface
Bind antigens to a B-cell activating the cell resulting in proliferation and formation of plasma and memory cells
Antibodies (Immunoglobulins - Ig) On Mast Cell Surface
Bind antigens causing Degranulazation - an exocytosis of granule contents which allow the release of histamine causing an inflammatory allergic reaction
Antibody Structure
Y shaped molecule with:
- 2 Identical Heavy chains
- 2 Identical Light chains
- Disulfide linkages and non-covalent interaction hold the heavy and light chains together
Antigen Binding Region
Variable Domain on an antibody at the tip of the Y shaped molecule; Here there are specific polypeptide sequences that will bind ONLY ONE specific antigen
Hypermutation
Each B-cell undergo this process of it’s antigen binding region to find the best match to the antigen; Only those B-cells that can bind the antigen with high affinity survive and provide a mechanism for generating specificity called Clonal Selection
Constant Region
Domain of the antibody that natural killer cells, macrophages, monocytes and eosinophils have receptors for to initiate the complement cascade
Naiive B-Cells
Have no yet been exposed to an antigen but wait in the lymph nodes for their particular antigen to come along
Primary Immune Response
- Plasma cells - large amounts of antibodies
2. Memory B-cells - wait in lymph node and will initiate secondary response if pathogen ever attacks again
Cell Mediated Immunity
Involves T-Cells which mature in the thymus
Positive Selection
Mature cells that respon to presentation of antigen on MCHC
Negative Selection
Causes apoptosis in cells that are self-reactive (activated by proteins that are produced by organism itself)
Helper T-Cells (CD4+)
Coordinate the immune response by secreting chemicals (Lymphokines) capable of recruiting other immune cells (like plasma, Cytotoxic T-cells and macrophages) and increasing their activity
CD4 Cells respond to MHC II - 4x2=8
**better at fighting extracellular infections
HIV
Loss of Helper T-Cells (CD4+) causing an inadequate immune response
Suppressor / Regulatory T-Cells (Treg)
Express CD4 and Foxp3 which tone dow the immune response once infection has been adequately contained; They have self tolerance and can turn off self reactive lymphocytes to prevent auto immune diseases
Cytotoxic T-Cells (Tc or CD8+)
Directly kill virally infected cells by injecting chemical that promote apoptosis into infected cells
CD8 Cells respond to MHC I - 8x1=8
Most effective against intracellular infections and viral infections
Memory T- cells
Lie in wait until next exposure to the same antigen; when activated there is a more rapid and robust response
Bacterial Infection Process With B-Cells
Extracellular Pathogen:
- Macrophages engulf the bacteria while releasing histamines. They digest the bacteria and present antigens on surface
- Cytokines attract inflammatory cells including Neutrophils and additional macrophages
- Mast cells are activated
- Dendritic cells present antigen to B-cells
- B-cells produce antibody and also create plasma and memory cells
- Antibodies travel through blood and tissue
- Antibodies tag bacteria for destruction
Bacterial Infection Process With T-Cells
Extracellular Infection
- Macrophages engulf the bacteria while releasing histamines. They digest the bacteria and present antigens on surface
- Cyotkines attract inflammatory cells including Neutrophils and additional macrophages
- Mast cells are activated
- Dendritic cells present antigen to T-cells
- T-cells (CD4+) activation
- Th1 and Th2 release interferon and help activate B-Cells
- Macrophages are activated and increase their ability to kill bacteria
Viral Infection Process in Infected Cell
Intracellular Pathogen:
- Produces interferons to reduce permeability of nearby cells (decreasing ability of virus to infect these cells)
- Reduce the rate of transcription and translations (decreasing viruses ability to multiply)
- Cause systemic symptoms; fever, muscle aches, fatigue, etc…
- Intracellular protein is presented on surface in conjunction with MHC-I
Body Response to Viral Infection
- CD8+ T-cells recognized MHC-I and the antigen resulting in injection of toxins in the cell to promote apoptosis
- Natural killer cells recognize the absence of MHC-I (when virus down-regulates the cell) and promote apoptosis
- Memory T-cells are created once the pathogen is cleared from the system
Self-Antigens
Proteins and carbohydrates present on the surface of every cell body; signaling immune system cells that they are not threatening and not to attack
Autoimmunity
Attacking cells labeled as “self” and fails to make a distinction between “self” and “foreign”
Hypersensitivity Reaction
Immune system misidentifies a foreign antigen as dangerous when it is not
*How allergies are created
Active Immunization
Immune system is stimulated to produce antibodies against a specific antigen
Natural Exposure
Antibodies are generated by B-Cells once an individual becomes infected
Artificial Exposure
Vaccines result in production of antibodies but the individual never experiences the actual infection; They receive an weakened or killed form of the microbe or part of the microbe protein structure
Passive Immunization
Transfer of antibodies to an individual (temporary because plasma cells are not transferred) - during breast-feeding or across the placenta
