Expression and secretion of RANTES by human peripheral blood CD4+ cells are dependent on the presence of monocytes

The cDNA for RANTES (an acronym for "Regulated upon Activation, Normal T cell Expressed and Secreted") was initially discovered by subtractive hybridization as a T cell-specific sequence. Consistent with it being a C-C (β) chemokine, RANTES is a monocyte chemoattractant. In addition, RANTES can chemoattract unstimulated CD4+/CD45RO+ memory T cells and stimulated CD4+ and CD8+ T cells with the naive and memory phenotypes in immunologically active sites. It has been shown that CD8+ cells are dominant sources of RANTES. Here we attempted to determine if CD4+ cells express and secrete RANTES alone, or if other accessory cells (activated monocytes) are needed to activate them. We found that when autologous monocytes are added to CD4+ cells and then stimulated with phytohaemagglutinin (PHA), the quantity of RANTES, in terms of transcription and translation of the protein, is significantly higher than the amount produced by the PHA-activated monocytes alone; isolated CD4+ cells stimulated with PHA do not produce any appreciable quantity of RANTES. When CD4+ cells are primed overnight with monocytes and then stimulated with PHA, they produce more RANTES compared to PHA-stimulated CD4+ cells alone. The influence that monocytes have on CD4+ cells to produce RANTES was confirmed when the physiological activator, tumor necrosis factor-α (TNF-α), was used. These data show that CD4+ cells need monocytes to express and secrete appreciable amounts of RANTES.