Body Defense System Flashcards
Blood cells involved in the immune system
Leukocyte:
- Neutrophils
- Eosinophils
- Basophils
- Monocytes
- B and T lymphocytes
- Plasma cells
Importance of immune system
Body defence against pathogens, infectious agents, viruses, etc.
Movement ofwhite blood cells through pores
Diapedesis: deformation of cells to pass through pores mediated by selectin
How do pores of endothelial layer change?
Size can be altered by presence of growth factors or cytokines
Chemotaxis
Movement directed by chemical concentration gradients
Granulocytes
Neutrophils
Eosinophils
Basophils
Neutrophils
Most abundant leukocyte. Neutralize infectious bodies by phagocytosis.
Eosinophils
Mobilized following parasitic infection. Release hydrolysis enzymes to weaken the parasite and release H2O2 to help detoxify inflammatory substances.
Basophils
Produce heparin. Facilitate removal of fat. Release histamine which activates inflammation and pain pathways for allergic reactions.
Two functional forms of immunity
Innate immune system
Adaptive of acquired immune system
How are infectious agents detected?
Damaged cells activate and attract phagocytic cells by releasing chemotactic factors
Innate immunity
Physical barriers and factors
Soluble compounds
Cellular component
Physical barriers
Skin
Physiological factors
Low pH or acid, increased temperature, oxygen tension
Soluble compounds
Lysozyme
Complement complex system
C reactive protein
Cytokines
Lysozyme
Enzymes that attack bacterial cell wall by cleaving molecules to disrupt integrity of cell
C reactive protien
Bind to c-peptides on bacteria to flag them for the complement system
Complement system
Compliments removal of pathogens
- Directly though activation of antibodies
- Contacting surface of pathogens
Cytokines
Biochemical messengers stimulate leukocyte activity
NK cells
Natural killer cells have no memory but is able to ducted viral proteins and target viral cells.
How to NK cells work?
Activated by interferons produced by viral cells and lymphocytes. NK cells bind to virus and release granules to form pores in the virus membrane which cause it to lyse
Phagocytic cells
Neutrophils and macrophages
Opsonization
Deposition of compounds (opsonins) on infectious agents to enhance its recognition. Multiple opsonins increase efficiency of detection.
Ex. C3B and antibody
Reticuloendothelial system
Network of neutrophils and macrophages in organs, bone marrow, spleen, and lymph node that move around in the blood stream and are attracted to foreign substances via chemotaxis
Tissues with high amounts of phagocytic cells
Skin and subcutaneous tissue Liver sinus Spleen Bone marrow Lymph node Alveoli
Adaptive immunity
Work in concert with innate immunity but provides more specific immunity against individual agents.
Able to remember past infections so it can deliver immunity faster due to a subsequent encounter.
Antibody structure
2 heavy chains and 2 light chains bound by disulphides bonds
How is an antibody bifunctional?
Has an antigen binding region (Fab domain)
Has a cell binding domain (Fc region)
Epitope
Specific binding site on a molecule that corresponds to a antibody
Specific antigen antibody reaction
Epitope matches Fab region
Cross reaction
Epitope slightly matches Fab region
No reaction
Epitope resembles no similarity to Fab region. Therefore antibody cannot bind to molecule to execute a immune reaction.
Immunoglobulin G
Most abundant
Targets toxins
Immunoglobulin A
In sero-mucus secretion (saliva, colostrum, milk, genito-urinary)
Immunoglobulin M
Binds to substrates to increase detection
Early antibody
Immunoglobulin D
On B lymphocytes
Trigger lymphocyte differentiation
Bind to specific antigens
Immunoglobulin E
Respond to allergens and parasites
Present on basophils and mast cells
Inflammatory
Humoral immunity
Mediated by B cells
Produce specific antibodies
Mature in bone marrow
Cell mediated immunity
T cells
Destroy invaders
Mature in thymus
How b and T cells work together?
B cells make antibodies
T cells destroy cells with specific antibodies
Clonal selection
Each B cell is only able to produce one antibody and recognize one antigen.
Binding of a specific antigen to a preformed B cell leads to B cell activation. Enlargement of B cell to plasma cell leads to proliferation of a corresponding antibody.
What happens to B cells that do not become plasma cells?
They form memory cells which have membrane components that recognize the same antigen; important to effectively fight a subsequent re infection
Secondary response
Rapid and potent antibody response to subsequent re infection due to presence of memory cells.
Adjuvence
Process of enhancing a immune response. Ex. Vaccines
Function of antibodies
Agglutinate multiple organisms into large aggregates
Neutralize molecule by binding to its active site
Opsonization
Complement activation (recruit proteins to form pore)
Major groups if T cells
Helper
Cytotoxic or killer
Suppressor
Helper T cells
Secrete cytokines including interleukins that help other T cells
Cytotoxic or killer T-cells
Bind to antigen on foreign cell and secrete perforin which mediates hole formation that causes apoptosis
How does the immune system distinguish between foreign cells and itself?
Membrane of cells belonging to the body contain histocompatibility molecules or human leukocyte antigens.
Where do histocompatibility molecules come from?
The major histocompatibility complex
Each person can only produce 3-6 types
Probability that these molecules are identical between two people is small. Reason for a lot of transplant rejections.
Class 1 major histocompatibility complex molecules
Produced by all cells except RBC
Class 2 major histocompatibility complex molecules
Only produced by macrophages and B cells
Which MHC molecules correlate with killer T cells?
Class 1
Which MHC molecules correlate with helper T cells?
Class 2
What are the different MHC receptors?
CD4 for helper
CD8 for killer
How are B cells activated?
Binding to antigen or binding to antigen presented on other leukocytes
Suppressor T cells
Regulatory T cells
Reduced helper T cell activity
Important for self immune tolerance
Immune tolerance
- Clonal detection: destroy lymphocytes with receptors for self
- Clonal anergy: lymphocytes do not attack self antigen
Hypersensitivity
Reaction to an antigen resulting in a pathological reaction
Antihistamines
Block allergen receptors to reduce reaction to allergens
Allergic reaction
- Allergen enters body
- Allergen binds to associated antibodies on lymphocytes
- Binding leads to activation and release of histamine
- Histamine causes inflammation
Inflammation
Vasodilation of local blood vessels
Increased permeability of capillaries
Increase interstitial fluid
Swelling
Walling off
Process of stoping spread of inflammation. Increased interstitial fluid begins to clot because of leaked fibrinogen. Creation of barrier.
What does inflammation attract?
Macrophages
Neutrophils
Monocytes differentiate to macrophages
Granulocytes produce more monocytes
