• Daniele C Nascimento, José C Alves-Filho, Fabiane Sônego, Sandra Y Fukada, Marcelo S Pereira, Claudia Benjamim, Dario S Zamboni, João S Silva, and Fernando Q Cunha.
• Departments of Biochemistry and Immunology, University of São Paulo, Ribeirao Preto, São Paulo, Brazil.
• Crit. Care Med. 2010 Aug 1;38(8):1718-25.

ObjectiveTo investigate the role of regulatory T cells in the modulation of long-term immune dysfunction during experimental sepsis. It is well established that sepsis predisposes to development of a pronounced immunosuppression. Nevertheless, the mechanisms underlying the immune dysfunction after sepsis are still not well understood.DesignProspective experimental study.SettingUniversity research laboratory.InterventionsWild-type mice underwent cecal ligation and puncture and were treated with antibiotic during 3 days after surgery. On days 1, 7, or 15 after cecal ligation and puncture, the frequency of regulatory T cells, proliferation of CD4 T cells and bacterial counts were evaluated. Fifteen days after cecal ligation and puncture, surviving mice underwent secondary pulmonary infection by intranasal inoculation of nonlethal dose of Legionella pneumophila. Some mice received agonistic glucocorticoid-induced tumor necrosis factor receptor antibody (DTA-1) before induction of secondary infection.Measurements And Main ResultsMice surviving cecal ligation and puncture showed a markedly increased frequency of regulatory T cells in thymus and spleen, which was associated with reduced proliferation of CD4 T cells. Fifteen days after cecal ligation and puncture, all sepsis-surviving mice succumbed to nonlethal injection of L. pneumophila. Treatment of mice with DTA-1 antibody reduced frequency of regulatory T cells, restored CD4 T cell proliferation, reduced the levels of bacteria in spleen, and markedly improved survival of L. pneumophila infection.ConclusionThese findings suggest that regulatory T cells play an important role in the progression and establishment of immune dysfunction observed in experimental sepsis.

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