Chapter 52-The Immune System Flashcards
Immonolgical tolerance
the bodys defenses must learn to recognize our own healthy normal cells, tissues and organs not not respond to these
Human pathogenic microorganisms
microorganisms that can cause disease in humans
-includes many viruses, some prokaryotes, and a few fungi, protozoa and worms
strict obligate pathogeninc
microorganism that when present in/on the body in sufficient dose in proper place will cause the disease associated with in most people (ie ebola virus, influenza virus, etc)
Infectious disease
a disease whose ultimate cause is due to a pathogenic microorganism
steps of pathogenesis
- exposure-pathogen must come from somehwere and arrive at a certain place in your body in sufficient dose
- Microorganism must move from portal of entry to place where it can replicate well (invasion)
- Microbial replication-when the microbe replicates the signs and symptoms of a disease first become noticeable and also when the bodys defenses become most apparent
- the bodys defenses are fully activated-object to kill the pathogen and prevent it from spreading
- exit of pathogen from host
Non specific defenses
present at birth and do not improve much with age
- general recognition of invading pathogens
- first response to exposure
Non specific defenses (types)
- Barriers-at body surfaces (portals of entry)
- -try to prevent pathogen from getting from the portal to site of replication
- -barriers=physical (our own cells and microbial flora), mechanical (tearing, blinking, sweating, urination), and biochemical (salt in sweat, stomach acid, fatty acids in sebum)
Specific defenses
adaptive or acquired immunity -develops over time -second line defenses, slower response but highly specific -involves cells and antibodys responsible for immunity
Skin
barrier
- largest organ of body
- provides nearly impenetrable barrier
3 other routes of infection
digestive, respiratory and urogenital tracts-barriers
-all three lined by epithelial cells, secrete mucus which traps microbes
Non specific (innate) defenses (internal)
- Phagocytic cells-neutrophils, macrophages, and dendritic cells
- inflamation
- fever
- complement proteins
- interferon
- various proteins
- coughing, sneezing
- vomiting, diarrhea
- natural killer cells
3 kinds of defending leukocytes (innate immunity)
1, macrophages-kill microorganisms through phagocytosis
- neutrophils-most abundant circulating leukocyte
- also use phgocytosis - natural killer cells
- do not attack invading cells directly
- induce apoptosis in target cell
Inflammatory response
marshalls bodys defenses at site of infection
- injured cells release chemical alarms
- cause nearby blood vessels to dilate and increase in permeability
- promote phagocyte accumulation
fever
elevated body temperature
- macrophages release interleukin-1
- causes hypothalamus to raise body temp
- promotes activity of phagocytes, while impeding microbial growth
- however, high fevers can denature proteins-dangerous
complement system
consists of about 30 different proteins that circulate in the blood in an inactive form
- becomes activated
- proteins aggregate to form a membrane attach complex (MAC) on surface of pathogen
- pathogen swells and bursts
antigens
molecule that provokes a specific immune response
-all molecules are antigens, but classified differently
self antigen
personas normal molecules in/on his cells
non-self antigens
molecules from anything else-microorganisms, cat hair, pollen, etc.
altered self antigens
tumors
epitopes
[art of antigen that is recognized as foreign by the specific defenses
epitopes are recognized by what
specific receptor proteins on the surface of the cells of the adaptive immune response
- B lymphocytes
- T lymphocytes
Specific defenses are characterized by what?
- specificity of recognition of epitopes on antigens on microorganisms
- wide diversity of antigens can be specifically recognized by different B and T lymphocytes
- Memory, where the immune system can respond more quickly to an antigen it has already encountered
- ability to distinguish self-antigens from non-self and altered self
The specific immune response
- recognition of foreign epitope on pathogen by B lymphocyte and/or T lymphocyte
- activation of those lymphocytes that confer protection against the pathogen
- effect:
- B lymphocytes become plasma cells and secrete antibodyy
- cytotoxic T cells attack intracellularly infected host cells and cancer cells
Humoral adaptive immunity
B lymphocytes or B cells with the help of other cells respond to antigens by secreting antibodies that bind to pathogens antigens
Cell-Mediated adaptive immunity
cytotoxic T lymphocytes or T cells with the help of other cells directly attack infected host cells or cancer cells
-if memory B and T cells form, immunity results
Immune recognition
receptors on lymphocytes bind specifically to epitopes on antigens on microorganisms
Active immunity
results form activation of an individuals own lymphocytes
-pathogen infection or vaccination
passive immunity
results from obtaining another individuals antibodies
- transfer of maternal antibodies across placenta
- antiserum with antibodies
Organs of the immune system
Primary Lymphoid organs
- bone marrow and thymus, locations where the B and t cells mature before being sent to secondary lymphoid tissues
- Secondary lymphoid organs-where lymphocytes come in contact with antigens
- -lymph nodes, spleen, and mucosal associated lymphoid tissue (MALT)
Primary Lymphoid organs
Bone marrow is site of B cell maturation
-thymus is site of T cell maturation
recognize epitopes only if they are combined with major histocompatibility complex (MHC) peptides
Secondary Lymphoid Organs
- Locations of these organs promote the filtering of antigens that enter any part of an individual’s body
- mature but naive B and T cells become activated in the lymph nodes
- spleen is site of immune responses to antigens found mainly in the blood
- MALT tissue include the tonsils and appendix
T lymphocutes
2 types
- cytotoxic T cells-kills infected host cels and cancer cells
- Helper T cells-helps B cells and cytotoxic T cells become activated
How cytotoxic T cells work
- recognize foreign peptides bound to self-MHC class 1 proteins
- clonal expansion and differentiate into activated cells and memory cells
- activated cells induce apoptosis in cells wtih same specificity as first cell and results in death of infected cell
How helper T cells work
respond to antigen that is taken up by an antigen presenting cell
- antigen complexed with MHC class 2 proteins
- activated T helper cells give rise to effector cells and memory cells
Humoral immunity begins..
begins when naive B cells in secondary lymph organs meet antigens
-B cells are activated when their surface lgs bind to a specific epitope on an antigen
Activation results in clonal expansion and differentiation into plasma and memory cells
-plasma cells produce soluble antibodies against the same epitope
5 classes of immunoglobulins
- lgM-first antibody secreted, promotes agglutination reaction and activates complemet
- lgD-present only on surfaces of B cells, serves as antigen receptor
- lgG-major antibody secreted during the secondary response, neutralizes antigens and promots their phagocytosis
- lgA-most abundant antibody
- lgE-binds to mast cells and basophils, allergens bind to it and it triggers allergic reaction
Primary immune response
first encounter with a foreign anitgen
- only few B or T cells can recognize antigen
- clonal expansion occurs, memory cells
Secondary immune response
secondary ecounter
-large clone of memory cells that can recognize the antigen
Allergy
refers to a greatly heightened response to a foreign antigen, or allergen (not on a pathogen)
- most common type is known as immediate hypersensitivity
- results from excessive lgE production
Blood type
Determined by antigens found on the surface of red blood cells
-ABO blood types-types A, B AB, and O
Immune system is tolerant of own RBC antigens
–ex. people with type A blood make antibodies against the type B antigen
autoimmune diseases
caused by the failure of immune tolerance
- result in activation of autoreactive T cells, and production of autoantibodies by B cells
- cause inflamation and organ damage
How do some pathogens evade the immune system
alter their surface antigens to avoid detection
