QSSMs are also thought to facilitate infection by other mechanisms and are able to influence the number and function of a specific type of immune cell known as an 'antigen presenting cell'. These cells are pivotal in allowing the immune system to recognise components of bacteria as foreign and thereby mount the appropriate response. It was found that large numbers of these types of cells underwent programmed cell death (cell suicide) in the presence of QSSMs compared to when QSSMs were absent. This mirrors the situation in blood sampled from patients with severe infections where there is a greater proportion of cell deaths among antigen presenting cells than other types of immune cell.