Chapter 1 Flashcards
(34 cards)
Targets both internal and external cell invaders
Internal=cell mediated immunity (CMI);cytotoxic cells
External= humoral; antibodies
What is Immunity?
State of protection from infectious disease
- Trap and process invader for recognition
- Bind and recognize invader
- Destruction
- Memory
2 layers of immunity
1st & 2nd lines of defense
- Innate; nonspecific
No memory, limited recognition, no lasting immunity - Adaptive; specific
4 types of barriers for innate immunity
- Anatomic
- Physiological
- Phagocytic/ endocytic
- Inflammatory
Anatomic Barriers of innate immunity
Skin and mucous membranes
Skin has 2 layers
- Dermis
a. thicker
b. connective tissue
c. sebaceous glands-microscopic glands that produce sebum (oily/waxy matter that lubricates and waterproofs skin and hair) - Epidermis
a. thinner
b. epithelial cells- renewed every 2-4 weeks
c. Keratin- fibrous structural proteins that assemble into bundles (intermediate filaments) *plugs mammary gland orifice
d. Produces a wide variety of anti microbial agent in order to control microbial populations
Mucous membranes
Consists of both outer epithelial layer and underlying connective tissue.
- saliva, tears, and mucous secretions provide
- washing action and anti microbial & antiviral components
Physiological Barriers
- Temp
- pH
- O2 tension
- soluble factors
a. lysozyme- (enzyme); cleaves peptidoglycan of bacterial cell wall
b. interferon- produced by virus-infecticed cells; induced anti-viral state of neighboring cells
c. complement (C’)-(enzyme system); damages membranes
d. lactoperoxidase- (enzyme); produces bacteriostatic products
e. lactoferrin- competes with bacteria for iron
f. peptides- disrupt microbial membranes and intracellularly.
Endocytosis
Ingestion of extracellular macromolecules.
- Pinocytosis- nonspecific
- Receptor-mediated endocytosis- selective
1. small regions of plasma membrane invaginate
2. form small endocytic vesicles
3. vesicles fuse together to form endosomes (acidic mechanisms facilitate dissociation and sorting)
4. primary and secondary lysosomes aid in digestion
5. small particles are eliminated by exocytosis
Phagocytosis
ingestion of molecules or organisms; done by specific cells
- membrane expands around matter
- phagosomes (large vesicles) are formed
- fuse with lysosomes
- contents degraded
- exocytosis
PAMPs
pathogen- associated molecular patterns; essential to the integrity, function, and replication of microbes.
- organisms recognize invading microorganisms by recognizing common microbial patterns on their surface
- distinguishing self vs. non-self
Examples of PAMPs
- LPS- lipopolysaccharide (associated with outher membrane of Gram- bacteria)
- Mannose, fucose, and other sugar residues (absence/presence, spacing b/t sugars)
- Techoid acid (associated with the peptidoglycan cell wall of Gram+ bacteria)
- N-formyl peptides (all prokaryotic protein sequences begin with a formyl- methionine)
PRMs
PRRs
PRMs- Pattern Recognition Molecules
PRRs- Pattern Recognition Receptors
**PRR-induced signals help direct the adaptive immune response.
Inflammation
Tissue damage cause by a wound or invasion by a pathogenic microorganism induces this complex sequence of events= inflammatory response.
Functions:
- delivery of effector molecules and cells to the sites of infection
- formation of a physical barrier to the spread of tissue damage of infection
- Would healing and tissue repair
Clinical signs: rubor (redness), tumor (swelling), calor (heat), dolar (pain)
Inflammation is characterized by
- Vasodilation (widening) of vessels leading to the site, and vasoconstriction of vessels exiting; causes redness and heat
- Increased vascular (capillary) permeability- influx of fluid and cells from capillaries; causes swelling (along with the migration of these cells to the site)
- Influx of white blood cells (including phagocytes)
Extravation of leukocytes (white blood cells) during inflammation involves:
- margination- adherence to endothelial cell wall
- diapedesis- emigration b/t capillary endothelial cells
- chemotaxis- directied migration through tissue to the site of the inflammatory response
How is inflammation initiated?
by chemical mediators from:
invading microorganism, damaged cells, plasma, white blood cells.
Examples:
*Acute phase proteins (serum proteins)- ex. C-reactive protein is produced by liver in response to tissue damage; binds to a component of the cell wall of many bacteria & fungi; activates complement; lysis, phagocytosis
- Histamine- binds receptor on venules and capillaries in induce vasodilation and increased permeability; released from a variety of cells in response to tissue damage
- Kinins- small peptide that induce vasodilation and increased capillary permeability
Natural Killer Cells
- Important first line of defense (Innate), although classified as lymphocytes
- can target virus-infected cells & buy time for adaptive immune response
- produce important intercellular messages (cytokines)
- found in blood- filtering organs (spleen, liver, lungs, bone marrow)
- Don’t express B or T cell surface molecules (CD4, CD8)
- No antigen-binding receptor; receptors are inhibitory or activating- inhibitory receptors are bound by normal surface molecules on healthy cells. Activating receptors promote killing by binding cell surface molecules induced by cell damage or that are encoded by intracellular pathogens
- have ability to recognize abnormalities on the cell surface
Acquired (Adaptive) Immunity
*Specificity, diversity, memory distinguishes self from non-self
Two major cell groups
- Lymphocytes
- Antigen presenting cells- trigger lymphocytes
2 main groups of organ systems
- primary lymphoid organs- lymphocyte maturation
2. secondary lymphoid organs- trap antigen where mature lymphocytes can interact with it
Populating the lymphoid organs are…
99% white blood cells
- only the lymphocytes (20-40% of white blood cells)possess diversity, specificity, memory and self/notself recognigtion
- rest are accessory cells
2 types of Lymphocytes
*B lymphocytes vs. T lymphocytes
B lymphocytes
associated with the humoral immunity branch of the adaptive immune system.
- Several important cell surface molecules
ex. Immunoglobulin- contain the antigen-binding site
ex. MHC II- so it can function as antigen presenting cell (to T helper)
- Interacts with soluble antigen via the surface immunogobulin
- presents antigen peptide on cell surface
- B cell activated by T cell (by cytokines)
- B cell divides repeatedly
- Differentiates b/t plama and memory cells
T lymphocytes
associated with the cell-mediated branch of the adaptive immune system.
- Several important cell surface molecules
ex. T cell receptor- membrane receptor for antigen; recognizes antigen only in association with a self molecule encoded by genes within the major histocompatibility complex (MHC)
ex. CD 3- all T cells
2 major lineages of T lymphocytes
- Helper T cells (Th)
- Th expresses CD4- recognizes antigen associated with MHCII on b cells - Cytotoxic T cells (Tc)
- Tc recognizes antigen associated with MHCI
