chapter 26 - innate immunity Flashcards
What is immunity?
the ability of an organism to resist infection
What are the two systems of immunity?
- innate immunity: nonspecific immunity, built in capability of multicellular organisms to target pathogens that are seeking to colonize the host
- adaptive immunity: acquired ability to recognize and destroy a particular pathogen or its product
What is competitive exclusion?
pathogens do not easily infect tissues because the harmless microbes limit available nutrients and sites for infection
What are the physical and chemical barriers to infection and why?
1- tight junction between epithelial cells that line body tissues inhibits invasion and infection
2- membranes are coated with a thick layer of mucous to trap microorgansims.
3- stomach acid inhibits bacterial growth
4- skin is salty and acidic, limiting bacterial growth
How does blood travel in the body?
gets pumped through arteries and capillaries
returns from the body through veins
What is the job of the lymph
It drains extravascular tissues into lymph capillaries and lymph ducts, then into lymph nodes throughout the lymphatic system
What is the correlation between the blood and lymphatic systems?
1- leukocytes and solutes pass from blood int he lymphatic system
2- lymph contains antibodies and immune cells, and empties into the blood circulatory system
What is plasma?
contains proteins and other solutes where blood cells are suspended
What is serum?
portion of blood that is not cells or clotting proteins.
What are the major cell types of blood?
- erythrocytes (all red blood cells)
- leukocytes (all nucleated cells - lymphocytes, granulocytes, monocytes)
What are hematopoietic stem cells?
precursor blood cells found in bone marrow and the gut
What is hematopoiesis?
differentiation of blood stem cells into different blood cells influenced by soluble cytokines and chemokines, proteins that direct immune cell production, function and movement
What are myeloid cells?
the are derived from a myeloid precursor cells
What are the two categories of myeloid cells?
- antigen-presenting cells:
engulf, process and present antigens to T-lymphocytes, which then initiates an adaptive immune response
(monocytes, macrophages and dendritic cells) - granulocytes:
contains toxins or enzymes that are released to kill target cells.
(neutrophils, basophils and eosinophils)
What is the function of natural killer cells?
function primarily in innate immunity, removing viruses and tumour cells by recognizing specific cell-surface molecules
What are lymphocytes?
specialized leukocytes invovled exclusively in adaptive immune response
What are the two types of lymphocytes?
- B cells: originate and mature in bone marrow (antibodies)
- T cells: originate in bone marrow but mature in thymus ((T cell receptors)
What type of organs are bone marrow and thymus?
lymphoid organs
What is microbial invasion?
the ability of a pathogen to enter host cells or tissues, multiply, spread and cause disease
What are phagocyte-pathogen interactions?
result in activation of genes and translation of proteins that eventually lead to the destruction of the pathogen
What is the mechanism of the recruitment of phagocytes?
- wound or tissue damage leads to microorganisms entering
- damaged cells release cytokines and chemokines
- phagocytes in response to cytokine-chemokine gradient are recruited to the site of injury and squeezed out of the blood capillaries
- the invading phagocytes are cleared by the phagocytes
What is the pathogen-associated molecular pattern?
pathogens have structures and molecules not found in or on host cells
What are patter recognition receptors?
leukocytes have membrane bound or soluble proteins that recognize pathogen-associated molecular pattern
What are toll-like receptors?
a class of pattern recognition receptors
recognizes and interacts with a specific pathogen-associate molecular pattern
What is the signal transduction in phagocytes?
upon activation of toll-like receptors, a leukocyte will start a phosphorylation cascade to transmit the activation signal to the nucleus activating transcription factors to turn on genes in response to the activation signal.
What is a phagosome?
the membrane-bound vesicle that surrounds the bacterium
fusing a lysosome forms a phagolysosome
What is inflammation?
a nonspecific reaction to noxious stimuli
What is the mechanism for inflammation?
- cytokines and chemokines released draw white blood cells to site of inflammation
- leukocytes release proinflammatory cytokines (IL-1)
- cytokines increase vascular permeability causing swelling
- pressure force fluids away from blood vessels into lymphatic system
What is systematic inflammation?
occurs when the inflammatory response fails to localize the pathogens and the reaction spreads throughout the body
What are prostaglandins?
chemical signals that raise the body temperatureW
What is the complement system?
a set of circulating, inactive proteins that are sequentially activated in response to a pathogen
What are the three pathways?
- sequence, orientation and activity of the components of the classical complement pathway
- the manose-binding lectin pathway
- the alternate pathway
What are the three outcomes of complement activation
- complement C3b coating the target making it easier for phagocytes to engulf it
- complement C3a diffuses to the surrounding area serving as a chemoattractant
- complement C5a binding to the target forming the membrane attack complex resulting in cell lysis.
What do natural killer cells do to defend against viruses
- nucleated cells have their surface MHC I proteins, virus-infected cells do not
- when encountering a cell without MHC I, a natural killer cell will activate and destroy it by producing granzyme and perforin
What is granzyme
an enzyme that induces apoptosis
What is perforin?
pokes holes in the target membrane
What are interferons?
small cytokine proteins produced by virally infected cells.
