IL-17 in protective immunity to intracellular pathogens

Abstract

The identification of a new T cell subset referred to as T helper 17 (Th17) cells and its role in protective immunity against extracellular bacterial infections is well established. In contrast, initial studies suggested that the IL-23-IL-17 pathway was not required for protection against intracellular pathogens such as mycobacterial infections. However, recent studies demonstrate that Th17-IL-23 pathway may play a crucial role in protective immunity against other intracellular pathogens by regulating the innate and adaptive immune responses. The current outlook on the role of IL-23-IL-17 pathway in protective immunity to intracellular pathogens is discussed here.

Acknowledgements

This work was supported by Children's Hospital of Pittsburgh, Pennsylvania Department of Health Formula Funding, AI075106, A1083541 from National Institute of Health, USA to S.A.K. The authors have no conflicting financial interests.

Figures and Tables

Figure 1 Role of IL-17 in protective immunity against intracellular pathogens. Involvement of Th17 pathway is not required for overall protective immunity against some intracellular pathogens such as M. tuberculosis, where activation of macrophages and bacterial killing takes place in the presence of functional IL-12 mediated Th1 responses (A). Th17 pathway is required for induction of IL-12 from DCs and generation of Th1 responses for macrophage activation and bacterial control in some pathogens such as F. tularensis LVS and C. muridarum (B). Th17 pathway is required for recruitment of neutrophils and bacterial killing in intracellular pathogens such as L. monocytogenes and S. typhimurium (C).

Table 1 Involvement of IL-17 in protective immunity to intracellular pathogens

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