Immune and inflammatory responses involve a whole array of cells and cell products which interact and mutually regulate each other. Many of these interactions are mediated by cytokines acting through specific receptors. Furthermore, lipid mediators such as PAF and the arachidonic acid metabolites LTB4 and PGE2 are known to affect several of the mechanisms involved in the regulation of the immune and inflammatory responses. In this paper, we review recent data from our laboratory illustrating the differential regulation of IL-6 and TNF alpha production and IL-2 receptor alpha and beta expression by these lipid mediators. We show that the regulation of these genes is both transcriptional and post-transcriptional, and that LT and PG can also be involved as second messengers in these regulatory processes.