Figure 2.

Ligation of phagocytic receptors has differential effects on TLR-mediated signalling. Ligation of dectin-1 by particulate ligands results in phosphorylation of the membrane proximal tyrosine residue of the ITAM-like motif by tyrosine kinases including hthe Src family.⁴⁸ Signals emanating from the ITAM-like motif are transmitted, by an unknown mechanism, to TLR-2 and perhaps TLR-6, promoting MYD88-dependent cytokine secretion.⁴⁶,⁴⁹ The zymosan-induced, dectin-1-mediated, production of ROIs is independent of the TLR system. The ITAMs of FcγRs become tyrosine phosphorylated, when ligated by either soluble antibody or antibody-coated erythrocytes, and then, by an unknown mechanism, exert an inhibitory effect on TLR-mediated IL-12 production.⁶³,⁶⁴