the FAB is connected to the FC by disulphide bonds
a native antigen can be linear or continuous
the BCR recognises antigen in association with Iga and igb, forming the BCRcomplex
what is the B cell co-receptor complex made up of
CD19, 21, 81
CD19
adaptor for activation
CD21
complementcoatedpathogen activates this protein
CD81
enhances signalling
IgM
primary and secondary, involved in complementfixation and agglutination
IgG
primary and secondary, complementfixation, can cross placenta
IgA
protects mucosal surfaces, monomeric in serum, dimeric in mucosalsites
IgE
inflammation, parasiticinfection, allergy
TCRs recognise antigen in the form of a complex of a foreginpeptide bound to an MHCmolecule
2 classes of TCR
ab: conventional, yg: nonconventional (abundant in gut mucosa)
the TCR is assisted by 2 sets of CD3 molecules and zeta chains, both of these are attached to ITAMS, that mediate the downstreamsignalling
cd8 binds to the alpha3 domain of MHC class 1
cd4 binds the beta2 domain of the MHC class 2
MHC molecules allow Tlymphocytes to detect cells that have ingested or have been infected with microorganisms, the T lymphocytes recognise the foreignpeptidefragment attached to the MCH and bind to it
in healthy cells, the MCH presents self peptides, and the T cells dontreact
MHC class 1 binds short peptides of 8-10 amino acids
MHC class 2 binds peptides of more than 15 amino acids
MHC genes are found on human chromosome 6
MHC 1 are expressed on cell surfaces of allnucleated cells
MHC 2 are expressed on the surfaces of professionalantigen presenting cells
co dominant expression
both parentalalleles of each MHC are expressed, this increases the number of different MHC molecules that can presentpeptides to Tcells
CD8 can kill any type of virusinfectedcell
CD4 helper T lymphocytes interact with dendritic cells, macrophages, and Blymphocytes
MHC restriction
Tlymphocytes (via TCRs) recognise antigens only when they are presented in association with self MHC molecules
self MCH and viral peptide
recognition of foreign peptide on targetcells and lysis