immunology Flashcards
what are 5 main components of the innate immune system
mechanical barriers physiological - stomahc acid, fever etc chemical mediators phagocytic leukocytes natural killer cells
what are the main points of the innate immune system?
first line of defence
produce local redness and swelling associated
non-specific response
what are the 3 pathways of complement activation?
classical, lectin or mannose binding pathway and alternative pathway
what is different about the mannose binding pathway?
involves manose bidning lectin which binds sugars on the surface of proteins to MASP 1 and 2
what is different about the alternative pathway?
it has autoactivation of C3 when in contact with bacteria
what does the complement do to help fight of pathogens
produce MAC to stab invading pathogens
produce anaphylatoxins
opsinisation of pathogens for phagocytosis by macrophages and neutrophils
attract neutrophils to the site of infection - complement products of C5a
what is the role of phagocytes in the immune system?
include macrophages, dendritic cells and neutrophils
they engulf pathogens by phagocytosis and express MHC II (macrophages) to make APC
secrete interleukin 1 and tumour necrosis factor (TNF)
what do neutrophils do in the immune system?
reside in the blood
activated and attracted to the site of infection
they have a double mechanism to bind to the blood vessel
neutrophils attack F-met peptides and once activated become phagocytotic and produce TNF
what do natural killer cells do in the immune system?
produce cytokines
destroy infected cells - uses fas ligand to bind to fas on target cell inducing apoptosis
where are B cells made?
derived from pluripotent hematopoietic stem cells in the bone marrow
lymphoid lineage
mature in lymph nodes
where are T cells made?
derived from pluripotent hematopoietic stem cells in the bone marrow
lymphoid lineage
mature in the thymus
how are B cells activated?
binding of antigen to receptors on the cell surface which causes the cell to divide and proliferate
a second signal is often needed
what is the main roles of B cells?
antibody production
activation of Tcells
activation of innate immunity
how are T cells activated?
antigen presented with MHC class I or II and CD80
what is the function of T cells?
release cytokines
what do cytokines do?
chemoattraction autoactviation augmentation of inflammation stimulation of Ab production by B cells activate macrophages
what is the role of BCR?
transduction and mediating internalization
what is the role of TCR?
responsible for recognising fragments of antigen as peptides bound to MHC
what is the role of CD4?
receptors on T helper cells that bind to MHCII
what is the role of CD8?
receptors on T cytotoxic cells that bind to MHCI
what is the role of CD28?
expressed on T cells, provide co-stimulatory signals required for T cell activation
what is the role of CD80?
co stimulatory molecule for T cell activation
What is the role of T cytotoxic cells?
have CD8 receptors which recognise MHC I
they destory cells by releasing enzymes which distrupt the cell membrane
what is the role of T helper cells?
have CD4 receptors which redcognise MHC II
activate B cells
activate phagocytes
produce Th1 and Th2 cytokines - they augment cell mediated and humoral immunity
what is the role of MHC I?
present endogenous antigens synthesised int he cytoplasm
display on surface membrane to CD8 receptors on cytotoxic cells
what is the role of MHC II?
Present exogenous antigens from extracellular material
displays antigen to CD4 receptors on t helper cells
what antibody types are monomers?
IgG, IgE and IgD
what does IgG do?
neutralises toxins
opsinisation
main Ig in the blood
what does IgE do?
antibody of allergy and antiparasitic activity
what does IgM do?
main antibody of primary responses
good opsiniser
what does I gA do?
secreted into mucus, tears and saliva preventing entrance of pathogens
what does IgD do?
found on B cell membrane
helps cell division
what type of antibody is a dimer?
IgA
what type of antibody is a pentamer?
IgM
how does immune memory work?
B cells remember antigen and when confronted a second time with the same antigen the ab response in much quicker
how does vaccination work?
relies on introduction of pathogenic source
immune response develops and provides long lasting immunity
booster injection may be needed
What is antibody switching?
immature B cells produce IgD and IgM
when activated B cells switch Ig class depending on location and function
how is diveristy of antibodies generated?
the variable region of the antibody made up of the building blocks: V (varible) gene D (diveristy) gene J (joining) gene somatic mutations changes affinity
what is autoimmunity?
missdirected adaptive immune repsonse
= loss of self tolerance
hypersensitivity reactions = over reaction of adpative immuen response
immunodeficiencies = components of immuen system are absent or defective
what is clonal deletion, during the development of B or T cells?
if developing B or T cells recognise self antigen they will be triggered to die, so this clone of cells is deleted
during T cell activation, which moleucles on the T cell recognise the Ag/MHC complex and 2nd signall on the antigen presenting cell?
T cell receptor (CD4 or CD8) recognise Ag/MHC and CD28 recognises the 2nd signal - CD80
what are the 3 main types of T cell?
cytotoxic T cell
T helper cell
Regulatory T cell
which antibdy class is common on mucosal surfaces such as in the GI tract and respiratory tract?
IgA
what molecule that is expressed on endothelial cells in repsonse to cytokines released by hperactive macrophages binds to a ligand on the surface of neurophils
selectin
which cytokines are released by hyperactive macrophages?
TNF and IL-1
what is required to stimulate primed macrophages to become hyperactive?
IFN-y and LPS (lipopolysaccharide from gran negative bacteria)
what is the difference between resting and primed macrophages?
primed macrophages express more MHC class II and take up larger objects by phagocytosis
where would you expect to find iC3b?
on the surface of a bacterial cell
oligmers of which protein form the pore through bacterial membranes as part of the membrane attack complex
C9
which pathway is activated by the sugars on pathogens such as bacteria, yeast and certain parasites?
lectin or mannose binding pathway
autoactivation of which complement protein is involved in the alternative pathway of complement activation
C3
viral peptides are loaded onto…….
MHC class I molecules
