MICE WITH A FLUORESCENT MARKER FOR INTERLEUKIN-2 GENE ACTIVATION

Production of interleukin (IL)-2 by T lymphocytes is one of the earlie st events during immune response. A mutant mouse strain was generated by replacing the IL-2 gene with a cDNA encoding green fluorescent prot ein (GFP). In this model, GFP fluorescence is readily detectable upon T cell activation and is mostly coexpressed with IL-2 at the single ce ll level. Thus, individual activated T cells can express the IL-2 gene biallelically. Upon stimulation through the T cell antigen receptor, CD4(+) cells separate into distinct GFP(+) and GFP(-) populations, bot h of which are capable of differentiating into either Th1 or Th2 effec ters. These mice allow noninvasive detection of IL-2 production by sin gle cells and analysis of the subsequent differentiative fate of these cells as an immune response develops.