Copyright q 1996, American Society for Microbiology Nuclear Factor of Activated T Cells Is Associated with a Mast

Interleukin 4 (IL-4), an immunoregulatory cytokine, is produced only by a subset of activated T cells and cells of the mast cell-basophil lineage. The production of IL-4 by mast cells likely represents a significant source of this protein in local immune-inflammatory responses in the skin, brain, gastrointestinal, and respiratory tracts, in which mast cells are prevalent. In the present study, the cis- and trans-acting elements that control inducible mast cell IL-4 gene transcription were examined and compared with those that function in T cells. We demonstrate that, as in T cells, sequences between bp 287 and 270 are critical for protein association and activation-dependent gene transcription and that this region (termed the activation-responsive element region) is the target of an inducible, cyclosporin A-sensitive, DNA-protein interaction. When assessed by electrophoretic mobility shift assays and UV cross-linking analyses, multiple proteins in both T- and mast cell nuclear extracts associate with the activation-responsive element in vitro, and some of these appear identical. However, distinct proteins are associated with each of the complexes as well. AP-1 family members are unique to the T-cell-stimulation-dependent complex, whereas mast cell complexes contain factors that are reactive with anti-nuclear factor of activated T cells p (NF-ATp) and anti-NF-ATc antibodies but have distinct molecular masses compared with those of T-cell-derived NF-AT. Furthermore, an anti-NF-ATp-reactive factor with a molecular mass of;41 kDa is present in the nuclei of unstimulated cells and binds independently o