therefore total signal strength ( stot ) will depend upon the concentration of tcr ( and other accessory molecules that bind to cell surface ligands , e.g . cd4 and cd8 ) on t cells , the concentration of antigen on apc or targets and the affinity of interaction between receptors ( a broad term incorporating tcr plus cd4 and cd8 ) and antigen .
C0039194
t cells
C0034790
tcr