Effect of prostaglandin E 2 on cytotoxic activity and granzyme a protease release by murine adherent IL-2 activated killer cells

Abstract

The effects of prostaglandin E 2 (PGE 2) have been studied on a highly purified population of murine IL-2 activated killer cells obtained by selecting plastic-adherent splenocytes (AK cells) after incubation with high doses of recombinant IL-2. AK cells were highly cytotoxic for YAC-1 target cells. The cytotoxic activity was detectable at one hour after initiation of the cytotoxic assay and then increased with time. Cytotoxic activity of AK cells was inhibited by the addition of PGE 2 or forskolin during the cytotoxic assay. When AK cells were generated in the presence of PGE 2, the yielding cytotoxic activity was lower than the one expressed by «regular» AK cells but were insensitive to the inhibitory effect of PGE 2 even if their lytic capability was still suppressed by forskolin. The presence of PGE 2 during the AK cell culture had no effect on the cellular proliferation. Moreover, using tetrazolium-based colorimetric assay which reflects the cellular activation, it was observed that AK cells cultured in presence of PGE 2 had an increased capacity to cleave the tetrazolium salt to formazan. Since the cytotoxic activity of killer cells is related to expression of serine esterase enzymes we evaluated the effects of PGE 2 on serine esterase (Granzyme A) release after one hour of incubation of AK cells either alone or in presence of PGE 2, YAC-1 cells or both. We observed that (i) AK cells spontaneously release granzyme A, (ii) the level of granzyme A was significantly increased when AK cells were incubated either with YAC-1 cells or PGE 2 but did not change when YAC-1 cells and PGE 2 were both associated with AK cells.