Immunology Flashcards
What are antigens?
Anything that causes an immune response
What is an antibody?
A protein molecule created by our immune system to target an antigen for destruction
What are cytokines?
Cell-to-cell communication proteins that control development, differentiation, & movement
What are cytokines produced by?
Leukocytes
What are interleukins?
13 cytokines that regulate immune response, inflammatory rxns, & hematopoiesis
What interleukins are responsible for fever?
IL 1 & 6
What IL causes acute-phase response?
IL-6
Tumor Necrosis Factor
- Activates neutrophils
- Mediates septic shock
- Causes tumor necrosis
What are chemokines?
- Type of cytokine released by infected/injured cells
- Signals neutrophils & macrophages to initiate immune response
What blocks virus replication?
Interferons
- Alpha, beta, & gamma subtypes
What interferon is the strongest? What produces it? What 3 things does it activate?
Gamma
- Produced by T cells
- Activates macrophages, natural killer cells, & neutrophils
IFN type I
What produces it & fxn
- Alpha & beta
- Produced by any cell type
- Induce viral resistance
- Can suppress T-cell responses & memory T cells (important in HIV)
IFN type II
What secretes it & fxn
- Gamma
- Secreted by natural killer cells & T lymphocytes
- Signals immune system to respond to infectious agents or cancerous growth
Immunity is conveyed by…
3 things
- Barriers
- Recognition
- Destruction
What are the 2 branches of immunity? & Define them
- Innate
- “natural, non-specific”
- FAST - Adaptive
- “specific, humoral, cell-mediated”
- SLOW
What is hematopoiesis?
Formation of cells that make up “blood”
Where does hematopoiesis occur in the embryo & fetus?
- Liver
- Spleen
- Thymus
Where does hematopoiesis occur after birth?
- Primarily bone marrow
- Lymphatic tissues
What are the components of innate immunity?
7 things
- Physical barriers
- Granulocytes
- Monocytes
- Macrophages
- Dendritic cells
- NKCs
- Complement cascade
What are the characteristics of innate immunity?
- Immediate
- Response does NOT increase w/ repeat exposure
What is the 1st level of protection?
Along w/ 3 examples
Physical barriers!
- Skin
- Mucous membranes
- Commensal bacteria
Describe the inflammatory response
- Damaged tissue &/or cell mediated histamine, prostaglandin & leukotriene release –> vasodilation & leaky capillaries
- Cell mediated heparin release –> decreased clotting
What does the inflammatory response result in?
- Increased blood flow to area
- Immunologic factors leak out of capillaries into interstitial space
What are adhesion molecules? What do they recruit?
- Membrane proteins that connect cells to other cells or ECM
- Recruit neutrophils to site of inflammation
Describe the effects of chronic inflammation
Chronic cytokine release & leukocyte infiltration –> release of lysozyme & free radicals –> tissue damage
What is the 2nd line of defense?
Granulocytes:
- Basophils
- Eosinophils
- Neutrophils
- Mast cells
What are the characteristics of basophils? What do they release?
- Least common
- Mature in bone
- Circulate bloodstream
- Allergic & helminth response
- Release histamine & heparin
What are the characteristics of eosinophils? What do they release?
- Derived from bone marrow
- Circulate bloodstream & organs (GI & RT)
- Active in allergic rxns, asthma
- Act as “antigen-presenting cells” (APCs)
- Weakly phagocytic
- Release H202 & other O2 radicals to kill microbes
- Release leukotrienes
What do eosinophils stimulate?
T-lymphocytes
Neutrophils
- Most abundant
- Circulate bloodstream
- “First responders”
- Active against bacteria & fungi
- Release cytokines to recruit monocytes & macrophages
- Strongly phagocytic
Neutrophil Extracellular Traps
“Throw out” extracellular fibers that bind bacteria
Mast cells (What do they release & where are they present?)
Release histamine & heparin –> inflammatory cascade
- Leave bone marrow as cells mature in tissues
- Present in tissues that are boundaries btwn “inside” & “outside”
- Massive release of histamine –> anaphylaxis
Mast cells will degranulate if…
- Injured
- Encounters antigen/allergen
- Exposed to complement proteins
Monocytes (What do they give rise to? Where do they develop, where are they stored?)
- “Agranular”
- Give rise to dendritic cells & macrophages
- Develop in bone marrow, 1/2 stored in spleen, 1/2 migrate to tissues & differentiate into dendritic cells & macrophages
What are the 3 primary fxns of Monos, macros, & dendros?
- Phagocytosis
- Antigen presentation
- Cytokine production
Dendritic cells (fxn)
- The strongest of the APCs
- Activate helper T-lymphocytes
What are the specialized dendritic cells in skin?
Langerhans cells
Macrophages (fxn, location)
- Large phagocytes
- Release TNF & ILs
- Act as APCs
- Present under skin, lungs, GI tract
What are the 3 stages of macrophage readiness?
A) Resting = cleaning up cellular debris
B) Primed = more active engulfing of bacteria, display fragments of bacteria for T cells
C) Hyper-activated = inflammatory cytokines –> macrophages enlarge & start destroying pathogens
After digesting a pathogen, a macrophage will present the antigen to what?
Helper T cell
- Antigen attached to MHC Class II molecule
What are specialized macrophages called? (Location, fxn)
Kupffer cells
- Within liver
- Destroy bacteria & old RBCs
Chronic activation of Kupffer cells leads to what?
Overproduction of inflammatory cytokine & chronic inflammation
NKCs
- Cytotoxic lymphocytes
- Active against viruses & cancerous cells
- Contain destructive enzymes
- In bloodstream, liver, & spleen
How do NKCs kill their target?
By releasing perforins & proteases –> membrane lysis or apoptosis
Major histocompatibility complex (MHC) proteins
- aka. Human Leukocyte Antigen (HLA)
- Cell surface molecules help immune system to determine if protein is “self” or “not-self”
- Bind antigen to cell surface & display for recognition of T cells
What are the 3 subgroups of MHCs?
I, II, & III
MHC key points
- Determines organ donation compatibility
- Autoimmune disease is a malfunction in this recognition system
- Participates in T & B cell activation (displayed in combo w/ a piece of antigen by APCs)
Acute phase proteins
- Produced by liver in response to inflammation induced release (by macrophages & T cells) of IL-1,IL-6 & TNF
- C-reactive protein
Complement system
Enhances ability of phagocytic cells to destroy pathogens
What are the 3 possible complement activation pathways?
- Classical (requires triggering)
- Alternative (activated at low level)
- Lectin pathway (requires specific type of triggering)
Complement is activated by what?
Antigens!
What organ makes complement proteins?
Liver
What is the most abundant complement protein in humans?
C3
Define: opsonization
Enhancing phagocytosis of antigens by “marking” them for destruction
Define: chemotaxis
Attracting & activating macrophages/neutrophils
- Inducing mast cells & basophils to degranulate
Define: lysis
Rupturing pathogen cell-membranes by forming the membrane attack complex (MAC)
What forms the MAC?
C5b forms complex w/ C6, C7, C8, & C9
What is the fxn of antibodies (adaptive immunity)?
- Block invader from binding
- Inactivate viruses & neutralize toxins
- Opsonization
Antibody structure
- 2 light chains
- 2 heavy chains
- Antigen binding sites
- Fab (variable) region
- Fc (constant) region
What are the 5 classes of antibodies?
“GAMED”
- IgG
- IgA
- IgM
- IgE
- IgD
IgM
- 1st class produced
- 1/2 life of 10 days
- Increased IgM = Recent exposure to antigen
Where is IgG found?
- Blood
- Lymph
- CSF
- Peritoneal fluid
Fxn of IgG
- Only class that crosses placenta
- Helps NKCs find their targets (opsonization)
IgG 1/2 life
- Longest of the Ig’s
- 23 days
- Used for passive immunization against rabies & hepatitis
When is IgG formed?
Late in the primary immune response
Where is IgA primarily found?
External secretions
What is the fxn of IgA?
- Protection of infant, present in breast milk
- Respiratory & GI tracts
IgE
- Binds to mast cells & basophils
- Increased in atopic individuals
- Increased in presence of parasites
What are the components of adaptive immunity?
- T cells & B cells, which are “cell mediated”
- Antibodies, which are “humoral”
- Complement
- APCs
What are the characteristics of adaptive immunity?
- Requires days to develop
- Response is specific to an antigen
- Develops “memory”
- Subsequent exposures result in more rapid & intense immune response
Primary lymphoid organs
Where immature lymphocytes (Bs & Ts) grow up & proliferate
- Thymus in children
- Bone marrow
Secondary lymphoid organs
Where antigens are presented to mature B & T lymphocytes to initiate adaptive immune response
- Spleen
- Lymph nodes
- Tonsils & adenoids
- Appendix
B-cells (fxn)
- Eliminate extracellular pathogens
- Acts as an APC
- Produces antibodies
T-cells (fxn)
Destroy intracellular pathogens
T-cell subtypes
- “Killer” T-cells (CD-8)
- “Helper” T cells (CD-4)
Fxn of “Killer” T cells
Cytotoxic, identify & kill cells infected w/ virus
Fxn of “Helper” T cells
- Activate killer T-cells
- Signal B cells to begin secreting antibodies
- Activated cell differentiates into effector & memory cells
Types of immunodeficiencies
- Acquired
- Congenital
