To determine the immunosuppressive effect(s) of cephalosporin cefonicid (CEFO) on human T-helper cells (Th), we exposed human peripheral blood mononuclear cells (PBMC) to various concentrations of CEFO during in vitro stimulation with a panel of T-lymphocyte stimulators that activate different Th/antigen presenting cell (APC) pathways. We evaluated the proliferation and IL-2 production induced by influenza virus (FLU), allogeneic lymphocytes (ALLO), xenogeneic mouse splenocytes (XENO) or phytohemagglutinin (PHA). The proliferative responses to FLU and XENO were much more depressed by CEFO than those to ALLO or PHA. After 7 days of culture with the highest dose of CEFO tested (200 mg/l) the stimulation index (stimulated/unstimulated culture) was near to 0 in FLU and XENO treated cultures, indicating that the response against these antigens was completely abrogated. The responses to ALLO and PHA were also impaired, but not abrogated (stimulation index >1). Since Flu and XENO utilize the CD4+Th/self-APC pathway our data suggested that this pathway was extremely sensitive to CEFO-induced inhibition both when the response requires memory Th cells (FLU) and virgin Th cell (XENO). The incubation with CEFO (200 mg/l) reduced the IL-2 production by XENO, FLU and ALLO to less than 20% of control cultures, while paradoxically increases to 120% the production by PHA.
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