Detrimental effects of T regulatory cell-promoting IL-2-anti-IL-2 complexes in staphylococcal toxic shock syndrome. (164.13)

Abstract

Abstract Menstrual or non-menstrual toxic shock syndrome (TSS), caused by the superantigen exotoxins of Staphylococcus aureus or Streptococcus pyogenes, is characterized by a robust activation of the immune system, systemic cytokine/chemokine storm, multiple organ failure and possibly death, if not treated promptly. We tested whether increasing the numbers of Treg in vivo by administration of IL-2-anti-IL-2 complexes (IL2C) could be beneficial in TSS. Administration of IL2C [prepared by incubating 1µg of IL-2 (Peprotech) and 5µg anti-IL-2 (eBioscience, clone-JES6-1A12) in a total 200 µl at 37oC for 30 min] on days 0, 1 and 2, caused a 3 to 4-fold increase in CD4+CD25+FoxP3+ Treg numbers in the spleens of HLA-DR3 transgenic mice by day 5. However, upon challenge with staphylococcal enterotoxin B (SEB, 50µg), compared to untreated HLA-DR3 transgenic mice, IL2C-treated mice produced significantly higher levels of IFN-γ (1714±1365 versus 6642±2253 pg/ml), MIP-1α (782±23 versus 2305±376 pg/ml,), MIP-1β, RANTES and TNF-α. SEB-induced mortality was also significantly increased in the IL2C treated group. While only 1/5 mice died in untreated group, 6/11 mice died in the IL2C treated group. In conclusion, even though administration of IL2C significantly increased the Treg numbers, such a treatment also increased their susceptibility to TSS. Hence, the benefits of T reg-promoting IL-2-anti-IL-2 complexes in TSS or related conditions need more stringent evaluation.