Immunity two Flashcards
list physical barriers
skin -physical barrier -sebum mucous membranes -with cilia for bronchi saliva and urine: wash
list chemical barriers
tears and saliva - lysozyme
urine and stomach acid - too acidic
other barrier?
commensal
3 properties of innate immunity
- Occurs relatively rapidly
- Non specific
- No immunological memory
how do immune cells come about
haematopoietic stem cells pluripotent stem cells myeloid progenitors -T -B -NK lymphoid progenitors -eosinophil -basophil -neutrophli -monocyte
what do basophils, eosinophils and neutrophilshave in common?
granula
short lived
found in blood (not abundant in tissues till recruited)
what happenst to monocytes?
go into tissues and turn into macrophages
what are the 3 phagocytic cells?
dendritic cells, macrophages, neutrophils
how is phagocytosis initiated?
pathogen associated molecular patterns and pattern recognition receptors bind
examples of pathogen associated molecular patterns?
lipopolysaccharides
carbs and proteins
how are intracellular pathogens gotten rid of?
natural killer cells
describe complement system
pathogen and complement proteins collide, triggers cascade of reactions that aids cells in identifying pathogens
steps in inflammatory response?
mast cells and macrophages –> histamines –> permeable capillaries
fluid, proteins, clotting factors enter tissue –> clotting
cells release chemokines which attract more phagocytes
phagocytes and monocytes phagocytose bacteria
healing
features of adaptive immunity?
- Occurs over time
- Specific – due to clonal selection and expansion
- Immunological memory
differences in clonal selection between t cells and b cells?
t cells - antigens attached to MHC markers on dendritic cells
b cells - antigens are presented intactly.
describe t cell receptors
2 pp chains, which variable and constant regions
helper t cell role?
cd4 receptors bind to antigens presented on MHC class II. clonal expansion - forms more helper T cels amd memory cells. releases cytokines which enables other cells to be activated
cytotoxic t cell role?
cd8 receptors bind to antigens presented on MHC class I barkers. clonal selection and expansion to cytotoxic t cells (perforin and granzyme) and memory cells -operate on cells that have already been infected.
describe B cell role
surface antigens bind to free antigens –> clonal selection and expansion –> memory B cells and plasma cells which produce antibodies.
MHC class II markers are found on
only APC’s
MHC class I markers are found on
all nucleated cells (including APCS)
describe structure of antibodies
constant region (carboxy terminus; contains antigen binding site) and variable region (amino terminus) light chain and heavy chain
IgM?
act first
opsonises pathogens and makes it more susceptible to phagocytosis (constant region recognised by phagocytes)
serum
IgG
act over some time
neutralise extracellular toxins and viruses
serum
IgA
serum and secretions
secreted across mucosal surfaces - gut and breast milk
IgE
found beneath epithelial surfaces.
describe the 3 non sinus segments
primary lymph follicle (B cells)
secondary lymph follicle (includes germinal centre)
paracortical area (T cells)
medullary cords (macrophages)
desciribe sinus areas
medullary sinus
marginary sinus
describe vessles
artery/vein
afferent and efferent lymph vessels
how do activated APC’s get to lymph nodes?
afferent lymph vessel
where are unactivated T and B cells?
flowing through blood vessels through lymph nodes
why do unactivated T and B cells flow through lymph nodes from time to time?
because there’s a higher chance that they;ll interact with APC that has their complementary antigen
what happen APC enters complementary helper T cell?
clonal selection and expansion of helper T cell. releases cytokines.
what happens to B cells in the lymph node?
parts of pathogen come through afferent lymph - if small on their own; if large through macrophages. B cells ingest and display them. Helper T cell’s CD4 receptors bind to B cells MHC II markers. This activates B cell; clonal selection and expansion occurs in the lymph node.
once helper T and b cells are activated, what happens to lymphocytes?
enter efferent lymph vessel, then thoracic duct, then bloodstream. follow chemokine gradient to the site of infection and kill. note: cytotoxic T cells still need to attach to MHC I markers of infected cells.
