What is immunity?
Defense against infection/disease caused by pathogens and their products
What are the two types of defense against pathogens?
There is innate immunity and adaptive immunity.
Present at the birth
Non-specific defense of the body (host)
Specific response of the body to a specific pathogen
What are the two defenses for Innate immunity?
First line of defense
Prevents pathogens from entering the body in the first place
Second line of defense
Helps eliminate pathogens that gain access to the body
What is the Epidermis?
The outer layer of the skin that provides nonspecific defense against colonization and infection by pathogens
Physical barrier to the entrance
A network of phagocytic cells called dendritic cells, phagocytize pathogens nonspecifically
What is the Dermis?
Contains collagen fibers that provide strength, hair follicles,
glands, blood vessels, and nerve endings
Chemical substances help defend against pathogens
Perspiration (sweat glands of the skin)
Antimicrobial peptides (defensins)
Sebaceous glands produce sebum, which lowers the pH of the skin
Blood vessels deliver defensive cells and chemicals
What is the role of mucous membranes in innate immunity?
Line the lumen of the respiratory, digestive, reproductive, urinary tracts: epithelium/deeper connective layer to provide support
The epithelium is a thin outer covering of the mucous membrane
Cells tightly packed prevent entry of pathogens
Shedding of cells carries microbes away
Dendritic cells reside below the mucous epithelium
What does the Lachrymal apparatus do?
Produces and drains tears
Blinking spreads tears and washes surface of the eye
Lysozyme in tears destroys bacteria
What are the two pathogens that will not be destroyed by stomach acid?
Clostridium botulinum and Staphylococcus Aureus.
What does Lactobacillus acidophilus do?
breaks down glycogen to produce lactic acid, decreasing the pH
What is the role of normal microbiota in innate immunity?
The normal microbiota competes with potential pathogens
Create an unfavorable environment
pH and oxygen availability
Lactobacillus inhibits overgrowth of Candida albicans
E. coli against Salmonella and Shigella (pathogens)
Promote overall health
Providing vitamins to the host
When does the second line of defense get activated?
The second line of defense functions when pathogens penetrate the first line of defense (skin or mucous membranes)
What are the three components of the second line of defense?
Inflammation, fever (processes)
What is plasma?
Plasma is mostly water containing many substances including
Iron-binding proteins (transferrin)
Blood clotting factors
Antibodies or immunoglobulins (adaptive immunity)
What is Serum?
the fluid remaining when clotting factors are removed
from the plasma
What is Hematopoiesis?
the process by which blood cells are formed
from stem cells of the bone marrow
What are Erythrocytes?
Cells that carry oxygen and carbon dioxide in the blood
What are platelets (Cell fragments)?
Involved in blood clotting
What are Leukocytes?
white blood cells
Involved in innate and adaptive immunity
What are the Granulocytes?
Neutrophils - Phagocytosis
Basophils- Production of histamine
Eosinophils- Production of toxic proteins against certain parasites; some phagocytosis.
What are the Agranulocytes?
Dendritic cells- Derived from monocytes; phagocytosis and initiation of adpative immune responses
Lymphocytes- Natural killer cells- Destroy target cells by cytosis and apoptosis
T-Cells - Cell mediated immunity
B-Cells Descendants of B cells produce antibodies.
What is leukocytosis?
A raise in the white blood cell count that can occur during a microbial infection.
What is leukopenia?
A decrease in the white blood cell count that can occur during a microbial infection.
What is a differential white blood cell count?
Percentage of each type of white cell in a sample of 100 white blood cells
What is diapedesis?
When cells leave the blood vessels by squeezing between cells lining capillaries
Explain the neutrophil, monocyte and dendritic cells role in defense components of blood and phagocytosis.
Dominate during the initial phase of an infection
Leave the blood vessels by squeezing between cells lining capillaries (diapedesis)
Monocytes mature into macrophages
As the infection progresses, macrophages dominate
Wandering macrophages leave the blood via diapedesis
Fixed macrophages are found in specific tissues/organs of the body
Mostly skin and mucous membranes
Initiate adaptive immune response
What are phagocytes?
Cell that are capable of phagocytosis.
What are the six stages of phagpcytosis?
List the 8 pathogens that can avoid phagocytosis.
Ability of a pathogen to cause disease is related to its ability to
evade/escape phagocytosis using different strategies
Haemophilus inflenzae type b
Plasmodium - malaria
Bacteria that are part of biofilms are more resistant to
phagocytosis such as Pseudomonas aeruginosa
What are the three Nonphagocytic killiers?
Killing by eosinophils
Attack parasitic helminths
Secrete toxins that weaken or kill the helminth
High numbers of eosinophils indicative of a helminth infestation
Killing by natural killer (NK) lymphocytes
Kill infected cells and tumor cells causing cytolysis or inducing apoptosis
Normal body cells are recognized by their membrane proteins similar to those of the NK cells
Killing by neutrophils
Produce chemicals (such as hypochlorite) that kill nearby
A strategy that leads to suicide of neutrophils
Generate extracellular fibers called neutrophil extracellular traps (NETs) that "trap" Gram positive and Gram negative bacteria, killed by antimicrobial peptides
What is inflammation?
Nonspecific defensive response to tissue damage from various causes, including microbial infection
Characterized by redness, heat, swelling, and pain
Increased permeability of blood vessels
Migration of phagocytes into the infected area
Blood clotting and repair/replacement of damaged tissue
What are two types of inflammation?
Develops quickly and is short lived
Beneficial (destroys, removes or walls off pathogens
Long-lasting and can lead to disease
What are omf;a,,atpry mediators?
released by damaged cells or other cell types (macrophages, and basophils/"platelets", mast cells), and include:
Prostaglandins and histamine
An increased vascular permeability during inflammation leads to what?
Increased permeability allows phagocytes to leave the blood stream and reach the site of infection (margination/diapedesis)
Leakage of fluids causes the swelling (edema) and pain associated with inflammation (pressure on nerve endings)
What is a fever?
A body temperature over 37°C
The most frequent cause of fever is an infection caused by bacteria or viruses
Results when pyrogens trigger the hypothalamus to increase the body's temperature
Various types of pyrogens
Cytoplasmic content of bacteria released by lysis
Phagocytes that have phagocytized pathogens
Constricted vessels carry less blood to the skin, causing it to feel cold to the touch (chill associated with fever)
What is the crisis of a fever?
occurs when the thermostat is reset to 37C and the body begins to cool by:
Lowering metabolic rate
Dilating blood vessels in the skin
What is the complement system?
a defensive system of proteins produced by the liver
Found circulating in blood and within tissues
Activation results in
What are the three ways the complement system can be activated?
The complement system can be activated in three ways
Contact with a pathogen
Mannose-binding lectin, MBL
What are Interferons?
proteins released in response to viral infections
Interferons activate NK cells, which kill virus-infected cells
What are the Interferon alpha and beta (Leukocyte-IFN and fibroblast-IFN)?
Trigger production of antiviral proteins in neighboring
uninfected cells, inducing an anti-viral state
What is the Interferon gamma (Immune-IFN)?
Stimulates activity of macrophages (macrophage activation