Kojima N, et al. - By measuring 63 cytokines in serum samples from a longitudinal sample of men who have sex with men and transwomen from Lima, Peru, researchers examined the connection between changes in cytokine concentrations and syphilis infection state. Forty-four participants with incident syphilis [defined as a rapid plasma reagin (RPR) titer that was ≥ 1:8 or a fourfold increase from the prior RPR titer, and a positive Treponema pallidum particle agglutination test] were identified from a cohort of 401 participants. Twenty pairs of cytokines (out of 1953 possible pairs) were identified that differed between active and treated syphilis. From those, 3 cytokine networks of interest were identified: an Eotaxin–Rantes–Leptin network, a Mig-IL1ra-Trail-CD40L network, and an IL12p40-IL12p70 network. Among men and male-to-female transgender women with active and treated syphilis, differences in cytokine profiles are present. Cytokine assays may be a potentially useful tool in patients with serologic syphilis reactivity to identify active syphilis.