Insights into the initiation of type 2 immune responses

Immunology. 2011 Dec;134(4):378-85. doi: 10.1111/j.1365-2567.2011.03499.x.


Type 2 immune responses, characterized by the differentiation of CD4+ T helper type 2 (Th2) cells and the production of the type 2 cytokines interleukin-4 (IL-4), IL-5, IL-9 and IL-13, are associated with parasitic helminth infections and inflammatory conditions such as asthma and allergies. Until recently the initiating factors associated with type 2 responses had been poorly understood. This review addresses the recent advances in identifying the diverse range of antigens/allergens associated with type 2 responses and the function, expression and sources of type-2-initiating cytokines (thymic stromal lymphopoietin, IL-25 and IL-33). We also discuss the latest findings regarding innate lymphoid cells, such as nuocytes, as early sources of type 2 cytokines and their importance in protective immunity to helminth infections. These developments represent major breakthroughs in our understanding of type 2 immunity, and highlight the increased complexity existing between the innate and adaptive arms of these responses. These additional steps in the type 2 immune pathway also offer potential targets for therapeutic intervention.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Adaptive Immunity / immunology*
  • Allergens / immunology
  • Animals
  • Antigen Presentation
  • Antigens, Helminth / immunology
  • Asthma / immunology
  • CD4-Positive T-Lymphocytes / immunology
  • Cell Communication / immunology
  • Cytokines / immunology
  • Humans
  • Hypersensitivity / immunology
  • Immunity, Innate / immunology*
  • Interleukins / biosynthesis
  • Interleukins / immunology*
  • Leukocytes
  • Lymphocyte Activation
  • Parasitic Diseases / immunology
  • Th2 Cells / immunology*


  • Allergens
  • Antigens, Helminth
  • Cytokines
  • Interleukins
  • thymic stromal lymphopoietin