Inhibition of IL-12 p70 production from primary human Mϕs by HHV-6. Human peripheral blood–derived Mϕs were pre-exposed to HHV-6 and then stimulated or not with IFN-γ plus LPS. Control Mϕs were not pre-exposed to HHV-6. Culture supernatants were analyzed for IL-12 p70 levels by ELISA 24 hours after LPS addition. (A) Mean results (± SD) of Mϕs from 6 donors pretreated with HHV-6 subgroup A (strain GS). (B) Mean results (± SD) of Mϕs from 4 donors pretreated with HHV-6 subgroup B (strain PL-1).