The MHC class II (Ia) molecules are heterodimeric cell surface glycoproteins that have a limited tissue distribution and are essential for an Ir. These proteins are known to both display a limited tissue distribution and be responsive to up-regulation by cytokines such as IL-4. To begin to identify the molecular basis for both of these phenomena in B cells, we performed a deletional analysis of the upstream region of the murine E beta gene. We show that there are several cooperating positive as well as negative control elements in the E beta upstream region. The sequence between -2679 and -66 is a strong transcriptional element containing several sequences that act synergistically as positive elements. The negative elements are located more proximal to the transcription start site. Furthermore, two consensus motifs, termed X and Y, which are located in the proximal upstream region of all class II genes, are necessary for the transcriptional activity of more distal elements. Additionally, we identify an IL-4-responsive element located within 666 bp upstream of the transcription initiation site.