B9 cells originated from, and are only available from, L.A. Aarden,
Netherlands Red Cross Blood Bank, Amsterdam, The Netherlands. To use the
cells you normally contact him and then he will either send them to you or
give you permission to get them from somebody local.
Simon Worrall
P.S. If you don't want to measure bioactivity you could use a commercially
available ELISA kit. In my experience you should do both as the plasma
concentration of IL-6 protein does not always correlate well with plasma
bioactivity.