SHP-1 is constitutively associated with the inhibitory receptor LAIR-1, which, in turn, is constitutively phosphorylated by Lck [74], although SHP-1 may also be activated by other ITIM-containing inhibitory receptors. Activation of SHP-1 allows it to inhibit antigen-induced TCR signalling either through direct dephosphorylation of the TCRζ chain, or dephosphorylation of downstream adaptor proteins such as Lck and ZAP70. Activating phosphate groups are shown as stars.