Several observations suggest that Neisseria gonorrhoeae, the bacteria that causes gonorrhea infection, can suppress the immune system, but how this pathogen achieves this is not clear. In Nature Immunology (article also published online), scientists have discovered that a protein called Opa52, which helps the bacterium bind to human cells, also plays a key role in shutting down the immune response.
Ian Boulton and Scott Gray-Owen from the University of Toronto, Canada, have shown that Opa52 from N. gonorrhoeae can bind to a receptor on the surface of CD4 T cells called CEACAM1. Binding of Opa52-expressing N. gonorrhoeae to CEACAM1 effectively silenced CD4 T cells by inhibiting their activation and proliferation in what would otherwise be stimulatory conditions. N. gonorrhoeae strains that did not express Opa52 were unable to inhibit CD4 T cell activation. These findings may not be restricted to gonococcal infection since N. meningtidis and Haemophilus influenzae, which both cause respiratory disease, also express proteins that can bind CEACAM1, but this awaits further investigation.
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