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Generation, Persistence, and Modulation of Th0 Effector Cells: Role of Autocrine IL-4 and IFN-γ

1998; American Association of Immunologists; Volume: 160; Issue: 11 Linguagem: Inglês

10.4049/jimmunol.160.11.5280

1550-6606

Kent Miner, Michael Croft,

Immunotherapy and Immune Responses

Abstract Many studies have classified CD4 responses into either Th1-like or Th2-like, based on cytokine secretion profiles, but little significance has been placed on Th0 cells. This has largely resulted from studies that suggested that Th0 populations primarily comprise individual Th1 and Th2 cells. Here, we show that priming of Ag-specific naive CD4 cells with moderate dose IL-4 generates a Th0 population that is evident after 3 days in vitro and becomes prevalent after successive encounters with Ag over a 9-day period. By intracellular cytokine staining, the majority (>60%) of effector cells generated in this way produce either IL-4, IFN-γ and IL-2, or IL-4 and IFN-γ without IL-2. Endogenous IFN-γ secreted over the initial 3 days of culture was critical for generating Th0 cells, since neutralization allowed IL-4 to induce differentiation into Th2-like cells. Successive encounters with Ag were required for generating Th0 cells, and their stability and persistence were governed by the balance of endogenous IL-4 and IFN-γ secreted during the later stages of differentiation. Studies blocking Fas-induced cell death showed that this process played no role in Th0 cell generation, and differential death of committed Th1 or Th2 cells was not required for Th0 persistence. These data suggest that Th0 cells can be as prevalent as Th1- or Th2-like cells after naive CD4 activation, that the relative levels of autocrine IL-4 and IFN-γ are important to the lack of commitment, and that not all cells are predestined to the Th1 or Th2 phenotypes early in the response.