In this study, our data suggest that MHC class II receptor-SE interaction up regulates MyD88, IRAK4, TRAF6, NF-kB and cytokine expression in monocytes. Although the precise role of MHC class II molecules in signal transduction remains unclear, overwhelming evidence indicates that MHC class II molecules serve as signaling proteins in diverse antigen-presenting cells such as B cells, dendritic cells, and monocytes. HLA-DR-specific antibodies and SEB, which bind directly to MHC class II molecules, induce IL-1 production in human monocytes and myeloid cell lines. Thus, MHC class II molecules serve as signaling proteins in diverse antigenpresenting cells. Anti-MHC class II antibodies induce early biochemical signals, like a rise in cyclic AMP accompanied by nuclear translocation of protein kinase C in murine B cells. Removal of introns from eukaryotic pre-mRNA is carried out by a large, dynamic macromolecular machine called the spliceosome. Although pre-mRNA splicing was once thought to be a distinct biochemical process, work in the last 10 years has done much to demonstrate that pre-mRNA splicing can occur co-transcriptionally as the pre-mRNA is being transcribed by RNA polymerase II. The temporal and spatial coordination of these processes affords the opportunity for factors involved in each process to influence the other. Indeed, recent work has established that molecular and functional interactions take place between the RNAPII elongation complex and the RNA splicing machinery. These interactions work to coordinate the two processes with one another in a manner that is thought to ensure efficient production and processing of mRNA. Understanding how these processes are coordinated is crucial for understanding gene expression. The polymerase carboxyl-terminal domain is important for coordinating pre-mRNA splicing and transcription. The CTD has been shown to physically interact with splicing factors and to positively regulate splicing in vitro and in vivo. Post-translational modifications of the polymerase CTD by kinases, phosphatases, and prolyl isomerases have been shown to affect co-transcriptional splicing through multiple mechanisms. The mammalian kinase complex P-TEFb is an essential regulator of transcription elongation and has multiple roles in coordinating transcription and pre-mRNA processing. P-TEFb, comprising CDK9 and its associated cyclin T1, facilitates release of stalled RNAPII into productive elongation through a variety of mechanisms, Fulvestrant including inhibition of transcriptional repressors, recruitment of positive elongation factors, and phosphorylation of the polymerase CTD at Serine 2 of its heptapeptide CPI-613 repeat, a modification associated with productive elongation. These activities are required for recruitment of splicing factors to the site of active transcription and stimulation of co-transcriptional splicing. The role of P-TEFb at the interface of splicing and transcription was highlighted by an important report in 2001. Here it was demonstrated that immunoprecipitates of P-TEFb containing the elongation factor Tat-SF1 and spliceosomal snRNPs stimulated transcriptional elongation of a human immunodeficiency virus-1 template. The stimulatory effect was dependent upon the ability of Tat-SF1 to associate with both P-TEFb and the U2 snRNA. This finding suggested a novel role for Tat-SF1 and the U2 snRNP in stimulating transcription. However, the detailed mechanism underlying this stimulatory effect remains unknown, and it is not clear if this interaction occurs in vivo in mammalian cells. The yeast homolog of Tat-SF1, Cus2, has been characterized in yeast as a U2 snRNP-associated splicing factor. Tat-SF1 and CUS2 share 46% sequence identity, and the proteins each contain two RNA recognition motifs, as well as an acidic C-terminal domain. The homology between CUS2 and Tat-SF1 has raised the intriguing question of whether Cus2 has a role in regulating transcription. Recently it was shown that deletion of CUS2 reduced influenza RNA synthesis in yeast cells infected with viral ribonucleoprotein complex components.