Figure 4.

Model for the involvement of sialic-acid-binding immunoglobulin-like lectin G (siglec-G) in danger signalling. It is proposed⁴⁸ that CD24 is complexed with siglec-G but does not exhibit inhibitory signalling in the absence of a danger signal such as HMGB1. When there is only pathogen-derived signal, the CD24–siglec-G complex is not engaged and the Toll-like receptor (TLR) is able to deliver activating signals to the immune cell without inhibitory signals from siglec-G. When there is a danger signal, such as HMGB1, both the CD24–siglec-G complex and TLR are engaged. Siglec-G becomes active and is able to suppress signalling from TLR and dampen pro-inflammatory responses.