Immune system Flashcards
Innate immunity
native/natural - doesn’t change much throughout lifetime
anatomic barriers
rapid-response mechanism
directs and activates adaptive system
Adaptive immunity
acquired/specific
mechanisms stimulated by exposure
slower response, later more powerful
Specialized cells in innate system
Monocytes and macrophages Neutrophils Dendritic cells Natural killer cells Basophils Mast cell Eosinophils
Which cells are phagocytic cells
Monocytes and macrophages
Neutrophils
Function of monocytes and macrophages
powerful phagocyte
secretes cytokines like Type 1 interferon alpha and beta = antiviral = apoptosis of infected cell
can synthesize complement - can replenish C3 (a complement protein) during infection
Function of neutrophils
circulating in blood
responde to site of inflammation via cytokine signaling –> phagocytic in tissue
Large numbers = the ‘army’
Phagocytic cells have receptors to recognize stimuli and release other signals for activation
pattern recognition receptors
G couple protein receptors
opsonin receptors
cytokine receptors
Where are dendritic cells located
close to epithelium where our mechanical barriers are
dendritic cells function
activated during infection –> travels to lymph node –> activates adaptive cells
primary professional antigen presenting cell (APC)
natural killer cells function
synthesizes Type 2 interferon gamma to activate macrophages
responds to intracellular microbes
produce interferon to kill virus infected cells and tumor cells
in a state of constant inhibition
When do natural killer cells lose inhibition
when MHC 1 are damaged (Tumor cells)
when MHC 1 are inactivated, not recognized, or destroyed (virus infection)
Basophils, mast cell, eosinophils function
located close to our tissues
against parasitic invaders (degranulation –> histamine)
signal WBC to come to site of infection
Virus or tumor
they do not have appropriate complexes expressed
they do express activating ligands
Anatomic barriers
skin mucosal lining mucus stomach acid tears lactic acid in women's vaginas
Where are complement proteins produced?
the liver
function of complement proteins
constantly circulating throughout body
augment innate and adaptive immune system (help to recruit other cells to the area)
there are several autoimmune disease where complement proteins are implicated in the problem
Cytokines
used to signal other cells or recruit other cells to the area
Histamine
vasodilator, induces chemotaxis
Enzymes
can cause degradation of pathogenic tissues
Which cells can recognized components of microbes that are important for infectivity of the pathogen?
innate immune cells, leukocytes, epithelial cells
Pathogen associated molecular patterns
structures on the pathogen that is recognized by innate cells. these structures are essential to microbes, cannot be mutated, and help microbes evade defenses
think scare person that will harm you
danger associated molecular patterns (DAMP)
molecules released by damaged cells/necrotic cells that leukocytes can recognize and respond to
our own tissue that is necrotic; think of a sick person that needs an ambulance
Pattern recognition receptors (PRR)
receptors on the leukocytes and epithelial cells that are able to recognized the PAMP and DAMP to initiate immune response
goal is to recognize a pattern on a pathogen
Toll-like receptors (TLR)
a group of well defined PRRs
can respond to extracellular microbes, ingested microbes, and cells ionized with microbes
Mannose receptor on macrophage
recognized mannose –> phagocytosis
CRP
it can activate our complement cascade and it is an opsonin so it can attract other inflammatory cells or WBC to the area
during acute phase response
binds to bacterial component –> activates C1q
Another mechanism to activate classical pathway
LPS binding proteins
recognized LPS on bacteria
mannose-binding lectin
mannose-binding lectin: binds to mannose on bacteria –> activates complement, complicit can kill bacteria directly (MAC) or attract phagocytes, opsonin
Complement activation pathways
can be activated from any type of pathogen but it generally will respond to extracellular pathogens
can also be activated in immune responses (autoimmune disease)
alternative pathway (innate) classical pathway (adaptive) lectin pathway (innate)
Alternative pathway
triggered by bacterial polysaccharides (LPS)
important in innate immunity
lectin pathway
lectin - protein that binds to carbohydrates (CHO)
Mannose-binding lectin – plasma protein that binds to microbial mannose (CHO)
Can activate classical pathway without antibody binding
rol ein innate immunity (recognize bacteria without adaptive immune system)
classical pathway
triggered by antigen-antibody bing (IgM or IgG) – typically IgM
part of adaptive immunity –> communication between innate and adaptive
Ca2+ or Mg2+ dependent
cannot be activated until we have already encountered this or until our body has started to produce antibodies to recognize this
Membrane attack couplex (MAC)
C6 + C7 + C8 + C9 + C5b = complex –> cell lysis
Complement fixation
once antigen-antibody binds to complement = complement fixation
Complement inhibition
proteins exist on host cells to prevent over activation & host cell destruction
Cytokines
chemical signals
may be released by cells to signal, activate and attract other immune cells
interleukins (IL) - between white cells
interferons (IFN) - mainly released from dendritic cells and macrophages
Tumor necrosis factor - from macrophages, neutrophils, etc
Type 1 interferons
IFN alpha and beta - mainly released from dendritic cells and macrophages
functions in cell signaling —> virus infected host cell undergoes apoptosis
Type 2 inferferons
IFN gamma – mainly from T helper cells and NK cells
activates macrophages
activates B cells –> IgG (allows B cells to class switch from IgA to IgG or to produce more antibodies)
Tumor necrosis factor
kills tumor and virus infected cells
activates and recruits other immune cells
MHC 1
present in all nucleated cells
presents endogenous peptides (self antigens, intracellular pathogens, cancer cells)
recognized by cytotoxic T cells (CD8+)
MHC 2
present in professional APCs
presents exogenous peptides (endocytose or phagocytoses pathogen, starts external to cell)
taken in by APC –> broken down –> presented on MHC 2
recognized by T helper cells (CD4+)
