Innate and Adaptive Immunity (complete) Flashcards
What is immunity?
Our body’s defense system against pathogens, foreign substances that cause disease
- responsible for maintaining the body’s internal homeostasis
- complex response
– response times vary from immediate to later
- two processes that work together:
– innate (natural)
– adaptive immunity
What are the organs involved in immunity?
- spleen
- thymus
- tonsils
- Peyers patches
- appendix
lymph nodes
What is the spleen?
largest of the lymph organs
has white and red pulp
What is white pulp
in the spleen
contains concentrated areas of the T and B lymphocytes, dendritic cells
What is red pulp?
in the spleen
where old or damaged RBCs are destroyed
What occurs in the thymus?
maturation of functional T-cells
What are tonsils?
collection of lymph tissue located at entrance to the digestive and respiratory tracts
- no afferent lymphatic vessels
What are Peyers patches?
- lymphoid tissues in the GI, respiratory, and urogenital tracts
- only contain B cells
- not encapsulated
What are lymph nodes? What is their function?
vessels that provide lymph - protein rich fluid
Function
- filter foreign material from the lymph before it enters the blood
- centers for the growth and response of the immune cells
- located throughout the body
Innate vs Adaptive immunity (just a photo)
What is innate (natural) immunity?
- non-specific part of the immune system
- no memory!
- plays a role in the inflammatory process, which can actually lead to disease
Cells involved:
- neutrophils
- monocytes/macrophages
- natural killer cells
What three types of barriers are in the first line of defense of innate immunity?
Physical barriers (skin, mucous membranes)
Mechanical barriers (coughing, sneezing)
Chemical barriers (tears, sweat, stomach acid)
Activation of complement system
What is included in the epithelial barriers of the first line of defense of innate immunity?
- closely packed cells, layers, constant shedding and protective layer of keratin
– salty acidic environment inhibits colonization - lysozyme: makes cells easier for phagocytosis
- mucous membranes: tight epithelial cells
– mucus traps and washes away along with saliva - cilia: move microbes towards throat to be expelled by coughing
- surfactants: in respiratory tract
– opsonize or tag the cells needed to have phagocytosis - GI tract goblet cells: secrete mucin
– hydrated form is mucus: traps pathogens for destruction
What is the second line of defense of innate immunity?
- inflammatory response
- antimicrobial proteins
- phagocytosis
What are phagocytic cells?
- neutrophils
- dendritic cells
- monocytes/macrophages
- natural killer cells
Neutrophils
- most important cell in innate system
- short lived; many are produced
- v important in phagocytosis
Eosinophils/basophils (mast cells)
- attack parasites which are too large for phagocytosis
- v important in allergic reactions
- mast cells can live for months
- v important in hypersensitivity reaction
Monocytes/Macrophages
- go to all tissues
- macrophages are mature monocytes; long lived
-
are in both innate and adaptive immunity
– first line in innate immunity - scavenger - final clean up
- major inhibitor of the adaptive immune response
What are dendritic cells?
- found in nose, lungs, mucosal lining of the GI tract and skin
- migrate through the lymphatic system
- provide major link between innate and adaptive immunity:
– takes the organism to B and T lymphocytes (APC)
– some can produce interferon to suppress viral replications - also involved in cell-mediated immune reactions (allergic type IE contact dermatitis)
think of it having little arms and grabbing organism and taking it to B and T lymphocytes
What are natural killer cells?
- subclass of granular lymphocytes
- innate immune system
- first line of defense: constantly roaming body
- can recognize and kill bacteria, viruses, stressed, or tumor cells
- release cytotoxic granules resulting in apoptosis
– perforin and granzyme - solicit help from other types of immune cells by releasing proteins in the blood
– cytokines
How natural killer cells work (photo)
What are cytokines?
- Proteins produced and secreted by most cells in the body
– interleukins (IL), interferons (IFNs) and tumor necrosis factor (TNF)
– can be pro-inflammatory (IL-1, TNF, IL-6) or anti-inflammatory (IL-10) - Act as chemical messengers
– aid in communication among cells
– are secreted and bind to receptors on targeted cells - Play a role in innate and adaptive immunity
- Not stored; are short-lived
- Are pleiotropic: can act on different cells, not just one
- Produce colony stimulating factors to induce different cell types in the bone marrow
What are chemokines?
- subgroup of cytokines produced by thymus and lymphoid tissue
– promote inflammatory response
– signaling - control the movement and positioning of immune cells (T cells, B cells, dendritic cells) in tissues and critical for function on innate immune system
- warn other host cells of danger
- too many can cause damage to cells and tissues
What is the complement system?
- groups of circulating plasma proteins that help defend against microorganisms
- serve as a bridge between innate and adaptive immunity
What does the complement system do?
- when activated: sets into play a series of events which end in lysis of pathogen
– activated when antibody contacts antigen - help in the disposal of immune complexed and by-products associated with inflammation
Three stages:
- initial activation phase
- amplification of inflammation
- late-stage membrane attack response
– cell lysis
What are antigen presenting cells (APCs)?
- group of immune cells that mediate the cellular response by processing and presenting antigens for recognition by certain lymphocytes (T cells)
- begin transition from innate to adaptive immunity (change from non-specific to specific)
What do APCs include?
macrophages, B lymphocytes, dendritic cells
- chop up the antigen and move it to surface for the MHC complex
- activate T cells
What are the functions of APCs?
- express the MHC molecules on their membrane
- involved in T-cell activation
- “present” the antigen to the immune system
What do natural killer cells (NK) do?
- innate immune system
- first line of defense against viral infections
- can recognize and kill infected, stressed, or tumor cells
- can activate and inhibit
– does not destroy normal cells - granules form pores in cell membrane and cause apoptosis
- granular lymphocytes
What is the major histocompatibility complex?
MHC
- enables the T-lymphocytes to determine “healthy vs unhealthy” cells
– recognition of self vs non-self
- large cluster of genes on chromosome 6
– divided into three classes (I, II, III) based upon function
– class II: expressed on APC
– class III: complement system
Is the MHC the same for everyone?
No. are unique and impact immune responses and susceptibility to certain disease
human leukocyte antigen (HLA), on chromosome 6, are proteins on cell surface and define a person’s tissue type
- proteins involved in antigen presentation
- encode for parts of complement system
What is adaptive (specific) immunity?
- considered to be third line of defense
- needs to be activated
- characterized by antigen-specific response
- relies on previous exposure to an antigen
– stronger
– more prolonged
What are the three types of adaptive immunity?
- humoral
- cell-mediated
- regulatory T-cells
What are antigens?
- substances which generate the response from the host
- called immunogens
- can be bacteria, viruses, parasites, pollen, poison ivy, bee stings
- has an epitope
- are over 10K proteins that can recognize the antigen
– antibodies are different on every cell
– 10 billion combinations to match unique shape
What is an epitope?
part of an antigen that binds to a specific antigen receptor on the surface of a B or T cell that triggers a cellular immune response
What are B cells?
B lymphocytes, plasma cells, antibodies
- designated as plasma/memory cells by helper T cells
– cells transform into antibody secreting plasma cells or memory B cells - plasma cells bind and remove unique antigen with help of effector cells
– known as antibody factories - lead to opsonization or tagging of cells for phagocytosis - memory cells go to peripheral cells for next exposure to antigen
- play a role in opsonization
What are antibodies (immunoglobulins)?
- are complex, y-shaped, glycoproteins
- produced by mature B lymphocytes
- specifically recognize and bind to a foreign antigen
What are B lymphocytes?
B cells
- mature in the bone marrow
- play a major role in humoral immune response
- differentiate into:
– plasma cells and produce antibodies (immunoglobulins)
– memory cells
Activation and class-switching of B cells (photo)
What are T lymphocytes?
T cells
- leave bone marrow early, go to thymus to mature
- play a major role in cellular-mediated immunity
Types:
- helper
- cytotoxic (killer)
- regulatory
What do macrophages do in adaptive immunity?
- gets rid of pathogens and infected cells through adaptive system
- APC: bring antigen to the lymphocytes
- acts like a recruiter
– produces signaling proteins that activate other immune cells
– releases cytokines/chemokines - scavenger: perform final clean up
What are the functions of antibodies?
- directly impeded the function of the pathogen
- neutralize secreted toxins and enzymes
- facilitate the removal of antigens by phagocytic cells
- participate in cell-mediated immunity
- activation of opsonization
- activation of inflammation
What are the 5 types of immunoglobulins?
IgG, IgE, IgM, IgA, IgD
What is IgG?
- most abundant of the circulating immunoglobulins (75-80%)
- only one which crosses the placenta and transfers immunity from mother to baby
- protects against bacteria, viruses, and parasite infections
- activates complement system
- enhances phagocytosis
What is IgM?
- accounts for 6-10%
- first one to appear in response to bacterial or viral infections
- largest of immunoglobulins
- when IgM present – usually sign of acute infection
- activates complement system
What is IgA?
- immunity at mucosal surfaces/body fluids
– saliva, tears, breast milk, bronchial, prostate, GI, vaginal secretions - primary defense against infections in mucosal tissues
- prevents attachments of microbes to epithelial cells
What is IgE?
- important in allergic and parasitic infections
- binds to mast cells/basophils
- binding to cells triggers histamine to be released and rest of inflammatory response and allergic reactions
What is IgD?
- antigen receptor to begin the differentiation of B lymphocytes
- least understood
- known to play role in activation of mast cells and basophils
What is humoral immunity?
process of making B cells
- signaling from T-helper causing B cell differentiation
What does humoral immunity do?
Works to rid body of microbes and toxins
- antigen-antibody complexes
- clumping of cells
- neutralization of toxins, bacteria, viruses
- destruction of pathogens
- adherence of antigen to immune cells
- phagocytosis
- complement activation
Has primary response and secondary response
What is the primary response of humoral immunity?
- primary response: cell waiting for antibody to be detected; clonal selection occurs
– first time exposed to microorganism - B cells differentiate into plasma cells which create antibodies
- activation takes 1-2 weeks and many get better during primary stage
- IgM is produced in large amounts, and then IgG produced
What is the secondary response of humoral immunity?
- secondary response: occurs with repeated exposure
- recognition occurs faster
- minimal IgM but large amounts of IgG
titers, booster shot
What is cell-mediated immunity?
- functions against microbes, parasites, bacteria, viruses which replicate inside cells where they cannot be destroyed by antibodies
-
T cells are the major player
– cytotoxic T cells: attacks and destroy target cells
– helper T cells (CD4): work to control cells where pathogen grows in the phagosomes of macrophages
— CD4 cells: secrete interferon – stimulates microcidal substance in macrophage – kills cell
What are clusters of differentiation?
- are cell surface markers/receptors
- expressed by cells at different stages of maturation and activation
- over 370 different ones
Helper T cells and their CD protein
- express CD4 protein
- direct B lymphocytes and macrophages
– helps in recognition of self vs non-self - secrete cytokines, chemokines – kill infected dead cells and stimulate new macrophages
- play a role in amplifying and activation of the humoral response
What CD protein do helper T cells express?
CD 4
Cytotoxic T (killer) cells and their CD protein
- express the CD8 protein
- once activated: search out and destroy antigens
- able to differentiate what are normal and what are bad
- cause apoptosis or programmed death
What CD protein do cytotoxic T (killer) cells express?
CD 8
