trast, NF-κB responded to PMA exposure by a rapid up-regulation followed by a subsequent down-regulation. Increased intracellular Ca2+ concentrations countered the down-regulation of NF-κB by PMA, while similar treatment with calcium ionophore resulted in a reduced NF-κB activity following induction with HK E. coli. In order to further study NF-κB activation, we considered two up-stream signalling proteins, PKC and Bcl10. P