L21 - the immune system Flashcards
what is the job of the immune system
repair damaged tissues
respond to infection
slow cancer growth
what is humoral immunity
secretion of protective substances eg antibodies into body fluids
what is cellular immunity
cellular response to infection (phagocytes etc)
list the physical barriers that prevent pathogen entry
skin
mucous
mucous membranes (cilia)
scabs
List chemical barriers that prevent pathogen entry
mucus
stomach acid
lysozymes in tears/saliva
briefly describe innate immunity
non specific
rapid
responds to infections (non self) & altered self (cancer)
can be humoral/cellular
what does the innate immune system promote
inflammation
briefly describe adaptive immunity
specific
slower than innate
humoral or cellular
has memory
list the cells involved in the innate immune system
- macrophages
2. neutrophils
describe features of macrophages
large
highly phagocytic
non specific (eat anything)
can produce new lysosomes
describe features of neutrophils
respond to infection
quicker than macrophages
die after disposing of target
what are the cells of the adaptive immune system
lymphocytes ( B&T cells )
what is the specific name for macrophages in the:
- liver
- bone
- kidney
- brain
- kupffer cells
- osteoclasts
- mesangial cells
- microglia
what does the adaptive immune system recognise?
antigens
where are lymphocytes found
circulating blood and lymph
where are lymphocytes activated?
in 2ndary lymphoid organs (mainly lymph nodes)
where are b cells produced
bone marrow
where are t cells produced
bone marrow
where do B cells mature
in bone marrow
where do T cells mature
in thymus
what is the general function of B cells
secrete antibodies specific to target antigen (humoral)
what is the general function of T cells
activated to induce direct cell mediated response by:
recruiting other cells
attacking themselves
how do T cells recognise antigens?
T cell receptors (TCR)
how many types of T cell are there
4
name the types of T cells
- helper T cells
- cytotoxic T cells (killer)
- regulatory T cells
- memory T cells
function of helper T cells
activate B cell response
activate the other 3 T cell types
function of cytotoxic T cells
specifically kill infected cells
function of regulatory T cells
help modulate responses
function of memory T cells
remember antigen for rapid future response
how are B cells activated
by the antigen aided by T helper cells
function of antibodies
- neutralise pathogen
2. facilitate uptake by phagocytes (opsonization)
what is opsonization
the action of B cell antibodies coating an antigen to facilitate its uptake by phagocytes
name the two types of B cells
- plasma cells
2. memory cells
what are plasma cells
activated B cells secreting antibodies
what are memory B cells
B cells that remember the antigen
what is an antigen
a substance that activates the immune system and may (or may not) be harmful
can be protein/lipid/carbohydrate
can induce T and/or B response
what are antibodies
glycoproteins (immunoglobulins) that interact with specific antigens
how many varieties of antibodies
5x10^3
characteristics of antibodies
- 2x heavy chain
- 2x light chain
- specific antigen binding regions
- FC region
what is the FC region
region of antibody involved in specific macrophage signalling
how are there so many combinations of antibodies
at the DNA level the light chain variable region can be spliced and recombined in many ways
characteristics of the T cell receptor
has a & B chain
10^8 types - due to recombination
how are T cells activated
if the antigen on an antigen presenting cell (of immune response) fits the T receptor
explain the process of T cell activation
- if antigen on APC fits T receptor clonal expansion occurs
- in clonal expansion many TH, CT and MT are produced
- TH aid B cell activation
explain process of B cell activation
- B cells bind to antigen when aided by TH cell
- clonal expansion of that specific B cell
- many plasma and memory B cells produced
what are antigen presenting cells? and what part of the immune response are they
innate
they are cells that engulf pathogens and express the pathogens antigen on their surface
what type of cells can be APCs
macrophages
dendritic cells
b lymphocytes
explain how APCs activate the adaptive immune response
- antigen taken up by phagocytosis into APC
- APC presents antigen on its surface
- APC migrates to lymphoid tissue and presents antigen to T cells
- if T cell has the specific receptor for antigen - immune response triggered
give some characteristics of dendritic cells
APC’s
reside in tissues but can circulate
specific names based on location(langerhans in skin)
can migrate to lymph nodes
what is a primary lymphoid tissue
where lymphocytes acquire ability for immune response (born and matured)
(bone marrow & thymus)
what is a secondary lymphoid tissue
sites of lymphocyte activation
list 3 secondary lymphoid tissues
lymph nodes
spleen
mucosa associated lymphoid tissue (MALT)
function of lymph nodes
screen lymph
function of spleen
screens blood born antigens
removes aged/defective blood cells
function of MALT
screens mucosa
how are T cells matured in thymus
- receptor added to T cell
- ensured that T cell not responsive to self antigen
- enters circulation
what is found in lymph nodes
phagocytic cells for non specific filtering
lymphocytes to interact with new found antigens
where are mature and immature T cells found in thymus
mature - medulla
immature - cortex
how does adult thymus differ to infant thymus
degeneration in adult as all needed T cells have been produced
where are b cells activated
follicles of lymph nodes
what is in the mantle zone of lymph nodes mainly composed of
resting B cells
where in the lymph nodes are T cells mainly located
para cortex
where is MALT
mucosa of many epithelial cells
tonsil
ileum
characteristics of MALT
can be aggregations or scattered lymphocytes
how do macrophages recognise bacteria
they have receptors that bind antibodies bound to the bacterial surface
