Overview Flashcards
Adaptive Immune System
- later, stronger, & more efficiently targeted response that eliminates organisms that survive the innate I.S.
- enhances effectiveness of certain innate immune mechanisms
Innate Immune System
- early response system that stops infection BEFORE significant replication & spead can occur
- essential for development of adaptive I.S.
Common features of Innate & Adaptive I.S.
- Recognition
- Communication
- Killing/Elimination Mechansims
- Regulation
Recognition
mostly a function of receptors in cells of I.S.
BUT ALSO
some host proteins can recognize foreign substances
Communication
allows cells to coordinate effective killing/elimination of pathogens
chemical mediators (“mediators”)
signaling molecules
Killing/Elimination Mechanism
some cells can kill invading pathogens. they are specialized for intracellular or extracellular pathogens.
some pathogens are just eliminated from the body
Regulation
the I.S. turning itself off and modulating its response to infections so it’s not excessive
Differences b/n Innate & Adaptive I.S.
Defining difference: RECOGNITION
Innate I.S. recognizes…
PAMPs
DAMPs
Pathogen-Associated Molecular Patterns (PAMPs)
common features of pathogens
ex: LPS peptidoglycan, CpG motifs, etc
Damage-Associated Molecular Patterns (DAMPs)
molecules released from dead or “stressed” cells or from breakdown of extracellular matrix
Adaptive I.S. recognizes…
specific sequences of proteins & polysaccharides (Antigens, Ags)
General Characteristic of all cells/molec. in I.S.
inactive until they become activated
How are I.S. cells activated?
by PAMPs or DAMPs binding to Pattern-Recognition Receptors (PRRs)
Adaptive I.S. cells are activated by…
a unique Ag binding to the Ag receptor in the cell membrane
PRR locations
- Plasma Membrane
2. Cytoplasm
Cells of Innate Immunity
- Sentinel cells
2. Effector cells
Sentinel cells
Location: body surfaces
Have PRRs that recognize pathogens that enter body.
-release mediators to recruit & activate effector cells
-some can also be effectors
Effector cell types
- Phagocytes
- Macrophages
- Neutrophils
effector cells
any cell that produces an effect OR performs a function directly related to killing/eliminating pathogens
Phagocytes
-most important effector cells in innate immunity
Phagocyte’s functions
- Internalize pathogens
2. Kill pathogens
“Professional Phagocytes”
neutrophils & macrophages
Macrophages come from…
blood monocytes
Innate I.S. mediators recruit…
antimicrobial proteins and leukocytes to magnify the response to a pathogen.
key process that Innate I.S. mediators regulate…
acute inflammation
Eosinophils
- release proteins that esp. damage the tegument (surface) of helmints
- contain acidophilic granules
Natural Killer Cells
-recognize & kill host cells that are ‘stressed’ by infection w/ intracellular pathogens
antimicrobial peptides
- found in plasma, tissue fluids, & cytoplasmic cell structures
- kill bacteria by forming pores in cell walls & membranes.
complement proteins
- found in plasma & tissue fluids
- work as system
- system forms mediators to start & enhance inflammation & protein complex which makes membrane pores in pathogen.
Acute Inflammation
-local response to injury/infection
effect of mediators in Innate I.S. (acute inflammation)
- increase blood vessels’ diameters
- allow plasma to leak into tissues
- activate leukocytes to escape from bloodstream to tissues
Lymphocytes
- recognize antigens w/ their special receptors
- almost all are part of Adaptive I.S.
- each responds to a specific antigen
Difference b/n PRRs & antigen receptors
- PRRs: in many cell types. all the same. recognize same PAMP/DAMP regardless of cell that expresses it
- Ag receptors: found only on lymphocytes. unique to each lymphocytes
Types of Lymphocytes
- B-cells
2. T-cells
B-cells
-discovered in Cloacal Bursa of birds
B-cell function
-produce antibodies (Abs)
B-cell Ag receptor
plasma membrane version of antibody they secrete when activated
T-cells
mature in Thymus
T-cell Ag receptor
- called a “T-cell receptor” (TCR)
- NEVER released from cell
Alias of antibody
immunoglobulin
Types of T-cells
- Helper T-cells (Th)
- Cytotxic cells (Tc)
- Regulatory cells (Treg)
Helper T-cells’ function
coordinate immune response through signaling molecules
Cytotoxic T cells’ function
kill other host cells that are infected w/ intracellular pathogens
Regulatory T-cell’s function
regulates/impedes immune response
Adaptive I.S. recognition
recognize antigen through binding of the antigen to the receptor
B-cell recognition
recognize antigens just as their are (in solution or on the cell surface)
T-cell recognition
ONLY recognize antigens that have been “processed” by another cell
dendritic cell
sample antigens, internalize & process them, THEN present them in a form that T-cells can recognize.
Antigen-Presenting cells
antigen processing cells
“Signal 2” in adaptive response
sends a survival signal to lymphocyte.
come from cells activated by inflammatory mediators, PAMPs, DAMPs
Signal 3 of adaptive immune response
determine which function activated lymphocytes differentiate into during proliferation
memory cells
lymphocytes that don’t perform function
resting lymphocytes that persist for a long time
Primary Lymphoid Tissues
where lymphocytes mature from progenitor cells into mature cells able to respond to an antigen
ex. bone marrow, thymus, cloacal bursa
secondary lymphoid tissues
where fully mature lymphocytes respond to antigens
ex: spleen, lymph nodes
humoral immunity
- transferred by serum
- mediated by antibodies
Cell-mediated immunity (CMI)
- immunity transferrable by lymphocytes
- mediated by T-cells
