Immunology Flashcards
Immunology
- the study of immunity
- ability to ward of disease and protect against environmental factors
- types
- innate
- adaptive
Innate immunity
- present at birth
- fast, general response
- no memory response
- includes:
- first line of defense
- second line of defense
Adaptive
- slow, specific response
- memory response
- Includes:
- third line of defense
First Line of defense
- skin
- mucous membranes
- body secretions
Skin
- physical barrier
- several layers of tightly packed keratinized epithelial cells - chemical barrier:
- sebum (oily substance)
- low pH 3-5
- Lysozyme: enzyme that breaks down bacterial cell walls
Mucous Membranes
Physical barriers
- mucus lines open body cavities
- ciliary escalator: lining of trachea to propel microbes upward toward throat
Body Secretions
- Lysozymes:
-found in tears, sweat, saliva, urine - Perspiration:
-flush microbes from surface - saliva
-flush microbes from teeth - gastric juice
-acidic pH 1-2
5: urine
-acidic pH 6
-Uric acid and hippuric acid (inhibit microbes) - Vaginal Secretions
-acidic pH 3-5
Cervical mucous (antimicrobial properties)
Second Line of Defense
- phagocytes
- inflammation
- fever
- antimicrobial substances
Phagocytes
cells that ingest other microorganisms and substances
- neutrophils (PMNs)
- Eosinophils
- monocytes
- dendritic cells
Neutrophils
- polymorphonuclear leukocytes
- highly phagocytic and motile
- first to respond to an infection
- can leave blood and go into infected tissue
Eosinophils
- somewhat phagocytic
- Produce toxic proteins against parasites
Monocytes
- not actively phagocytic in circulating blood
- mature in tissues–> macrophages
- macrophages
- Fixed (histiocytes): stay in certain tissues or organs’
- free (wondering): motile, roam tissues, gather at sites of infection
- macrophages
Dendritic cells
- phagocytic
- initiate adaptive immunity (antigen presenting cell)
Mechanism of phagocytosis
- chemptaxis
- adherence
- ingestion
- digestion
chemotaxis
chemical attraction to microbes
adherence
- contact between phagocyte and microbe
- toll-like receptors (TLRs): protein receptors on phagocytes that attach to PAMPs on pathogens
- PAMPs: pathogen associated molecular patterns
- ex. LPS, flagellin, peptidoglycan
- binding causes release of specific cytokines
- cytokines recruit additional phagocytes
- faciliated by opsonins
- opsoninis: proteins that coat and promote attachment
Ingestion
pseudopods form and engulf microbe in a phagosome
Digestion
phagosome fuses with lysosome–> phagolysome
microbe is digested by hydrolytic enzymes
indigestible material (residual body) expelled
Inflammation
- cardinal signs/symptoms
- redness
- heat
- swelling
- pain
- caused by:
- tissue damage
- infection
function:
-destroys/slowdown pathogens
Inflammation steps
- chemicals released by damaged cells
- vasodilation
- increased permeability
- chemotaxis (attracting phagocytes)
- phagocytic migration
- margination (phagocytes stick to endothelium)
- Diapedisis (phagocytes squeeze through endothelium) - Phagocytosis
- Tissue repair
Fever
Abnormally elevated body temperature
Caused by:
- Pyrogens:
- Exogenus pyrogens: products of pathogens
- Endogenous pyrogens: products of leukocytes (i.e. Interleukin 1)
Actions: adjusts hypothalamus (thermostat) to higher temperature
Results in:
- constricting blood vessels to skin
- increased rate of metabolism
- shivering
Benefits of moderate fevers
- inhibits/ slows pathogen growth
- speeds up tissue repair
- intensifies actions of interferon
Complication of high fevers
- Tachycardia
- increased metabolic rate –> acidosis
- dehydration
- seizures
- neurological damage
Complement system
- Group of over 30 proteins found circulating in blood serum
- acts in cascade
- Destroy microbes by:
- inflammation (3a)
- phagocytosis (opsonization) (C3b)
- cytolysis (C3b)
Complement activation
- classical pathway
activated by certain antigen-antibody complexes - alternative pathway
-activated by interaction between complement proteins and pathogens
Interferon
- Antiviral proteins
- produced by:
- macrophages
- lymphocytes
- virus-infected-host cell
- function: interfere with viral replication, signals to neighboring cells to produce anti-viral proteins
Third line of defense
involves an immune response to specific antigens
antigens
molecules that cause an immune response
-antigenic determinant (epitopes): area of an antigen that causes the response
Antibodies
- immunoglobins (Ig)
- proteins produced in response to antigens
- function: recognize and bind to antigens
- structure:
- 4 protein chains
- 2 identical heavy chains
- 2 identical light chains
- chains joined by disulfide links
- 4 protein chains
Antibodies structure
- Y shape
- variable region: tips of Y arms, binds to epitopes
- constant region: lower portion of arms and stem
- Fc region: stem of Y, important for immunological reactions
classes of antibodies
IgG, IgM, IgA, IgD, IgE
IgG
- monomer
- Abundance: 80% of antibodies
- enhances phagocytosis, neutralizes toxins and viruses
- protects fetus and newborn (transplacental)
IgM
- pentamer
- Abundance: 5-10% of antibodies
- especially affective against microbes
- First antibodies produced in response to initial infection
IgA
- dimer
- abundance: 10-15% of antibodies
- localized protection on mucosal surfaces
IgD
- monomer
- abundance: 0.2% of antibodies
- located on B cells
IgE
- monomer
- abundance: .002% of antibodies
- allergic reactions
Types of antigen-antibody reactions
Agglutination: causes antigen to clump together
Neutralization: block virus, toxic, and bacteria binding sites
Complement fixation: binding activates complement cascade
Opsonization: coats antigen to enhance phagocytosis
Lymphocytes
Cells that produce immune response, found in lymphoid tissue
- Types:
- Natural Killer cells
- B cells
- T cells
Natural Killer cells
- part of innate immunity (non-specific)
- destroy target cell by cytolysis
B cells
- differentiate and mature in red bone marrow
- involved in humoral immunity (antibody) response
T cells
- differentiate and mature in thymus
- involved in cellular response
Antigen presenting cells (APC)
- present antigens to T cells
- contain Major Histocompatibility Complex II (MHC II) on surface (identifies cell as “self”)
- e.x. dendritic cells, activated macrophages, B cells
B cell response Process
- each b cell has a specific b cell receptor for a specific antigen
- b cell is exposed to antigen
- englufs and presents antigen on MHC II to activated T-helper cell
- T-helper cell activates B cell via interleukin 2
- activated b cell divides:
- plasma cells: produce antibodies
- memory cells: remain in body, can later be stimulated if encounters same antigen
Primary Reponse Process
- plasma cells produce antibodies that circulate in blood and lymph
- antibodies bind and neutralize antigen
Secondary response process
- memory cell activated by the same antigen
- activated b cells divides–> plasma cells
- plasma cells produce antibodies that circulate in blood and lymph
- antibodies bind and neutralize antigen
Secondary vs primary response
- faster
- more antibodies produced
- more sensitive
- last longer
T cell response Process
- each t helper cell has a specific t cell receptor (TCR) for a specific antigen
- APC engulfs antigen and presents antigen on MHC II to t helper cell
- APC releases interleukin-1 to activate t helper cell
- activated t helper cell release IL-2 to activate other t cells
T helper cells
- commander of entire system
- produce various cytokines
- activate variety of t cell, b cells, macrophages, NK cells
Cytotoxic t cells
when activated–> cytotoxic t lymphocyte (CTL)
CTL: destroys virus infected cells on contact
T regulatory cells
turn off immune response (prevent autoimmune response)
Memory t cells
recognize antigen in future infection for faster response
Types of immunity
active vs passage
natural vs artificial
Active vs passive
- active immunity
- due to individuals own immune response
- long lasting - Passive immunity
- due to another person’s immune response
ex. obtaining others antibodies
- short lasting
Natural vs Artificial
- Natural immunity
- due to natural exposure to antigens - Artificial immunity
- due to artificial exposure to antigen (vaccine)
Vaccines
- suspension of pathogens or antigens used to stimulate an immune response
- Types:
- whole unit vaccines
- subunit vaccines
- toxoid vaccine
- conjugated vaccines
Whole Unit Vaccines
Contain whole pathogens
- inactivated pathogens
- killed bacteria or viruses - live attenuated pathogens
- weaken microorganisms
Subunit vaccines
antigenic fragments of microbes
toxoid vaccines
inactivated toxins
Conjugated vaccines
Antigen combined with a protein to boost immune response
