Enhancement by monocytes of perforin production and its gene expression by human CD8+ T cells stimulated with interleukin-2.

Pore-forming protein (PFP) is an important effector molecule for cytotoxicity mediated by cytotoxic T cells and NK cells. In the present study, the effect of monocytes on PFP production by interleukin-2 (IL-2)-stimulated T lymphocytes was examined. Highly purified lymphocytes (> 99%) and monocytes (> 90%) were isolated by centrifugal elutriation from peripheral blood of healthy donors, and, CD4+ and CD8+ cells were isolated from the purified lymphocytes by using antibody-bound magnetic beads. PFP production was quantitated with a universal microspectrophotometer in combination with immunostaining using anti-PFP antibody. Monocytes did not produce any PFP. High levels of PFP production were observed in CD8+ cells, but not CD4+ cells after incubation for 4 days with IL-2. Addition of monocytes to cultures of CD8+ cells resulted in significant augmentation of PFP production after 3 days' stimulation with IL-2. Monokines (TNF alpha and IL-6) caused a significant increase in PFP production by IL-2-stimulated CD8+ cells. Northern blot analysis revealed that the PFP mRNA levels was enhanced by stimulation with IL-2, and that addition of monocytes to cultures of CD8+ cells plus IL-2 augmented their PFP mRNA expression. These observations suggest that monocytes are important in in situ regulation of the CD8+ T cell-mediated cytotoxic response through production of PFP.