IL-2 limits IL-12 enhanced lymphocyte proliferation during Leishmania amazonensis infection

Authors

Amanda E. Ramer-Tait, University of Nebraska-LincolnFollow
Christine A. Petersen, Iowa State UniversityFollow
Douglas E. Jones, Iowa State UniversityFollow

Date of this Version

2011

Citation

Cell Immunol. 2011 ; 270(1): 32–39. doi:10.1016/j.cellimm.2011.03.016.

Comments

Copyright 2011 Elsevier. Used by permission.

Abstract

C3H mice infected with Leishmania amazonensis develop persistent, localized lesions with high parasite loads. During infection, memory/effector CD44^hiCD4⁺ T cells proliferate and produce IL-2, but do not polarize to a known effector phenotype. Previous studies have demonstrated IL-12 is insufficient to skew these antigen-responsive T cells to a functional Th1 response. To determine the mechanism of this IL-12 unresponsiveness, we used an in vitro assay of repeated antigen activation. Memory/effector CD44^hiCD4⁺ T cells did not increase proliferation in response to either IL-2 or IL-12, although these cytokines upregulated CD25 expression. Neutralization of IL-2 enhanced CD4⁺ T cell proliferation in response to IL-12. This cross-regulation of IL-12 responsiveness by IL-2 was confirmed in vivo by treatment with anti-IL-2 antibodies and IL-12 during antigen challenge of previously infected mice. These results suggest that during chronic infection with L. amazonensis, IL-2 plays a dominant, immunosuppressive role independent of identifiable conventional T_reg cells.