The initial response of CD4+ IL-4-producing cells.

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Naive CD4(+) T cells are known to produce IL-4 in vitro, potentially initiating T(h)2 responses in vivo.
• Studying these IL-4-producing cells in vivo is challenging due to their low numbers early after antigen exposure.

Purpose of the Study:

• To track and characterize early CD4(+) IL-4-producing T cells in vivo.
• To establish a reliable method for identifying and analyzing these cells ex vivo.

Main Methods:

• Utilized IL-4/green fluorescence protein (GFP) reporter mice (G4 mice) for tracking IL-4-producing cells.
• Developed and validated a flow cytometry method to quantify GFP(+) cells.
• Performed fluorescence-activated cell sorting (FACS) for detailed analysis of sorted cells.

Main Results:

• Established flow cytometry method effectively identified activated CD4(+)GFP(+) cells.
• Sorted CD4(+)GFP(+) cells expressed T(h)2 cytokines (IL-5, IL-13) and transcription factors (GATA3, c-maf), lacking IFN-gamma mRNA.
• Derived cell lines from sorted cells demonstrated antigen specificity.
• Confirmed that the majority of responding GFP(+) cells were indeed CD4(+) T cells.

Conclusions:

• Provided direct ex vivo evidence that a small population of naive CD4(+) T cells produces IL-4.
• Demonstrated that these IL-4-producing naive CD4(+) T cells initiate T(h)2 responses.
• Validated a novel method for studying early T(h)2 cell responses in vivo.