Sepharose-C3

Synthesis of complement components C5, C6, C7, C8 and C9 in vitro by human monocytes and assembly of the terminal complement complex

Monocytes cultured under serum-free conditions secreted protein which bound covalently and non-covalently to agarose beads, an activator of the alternative pathway of complement. There was a significantly binding of monoclonal anti-C3c antibodies, polyclonal anti-C5, anti-C6, anti-C7, anti-C8, and anti-C9 antibodies, and of a monoclonal antibody against a neoantigen of polymerized C9 to agarose beads incubated with the monocytes for 24, 48, 72 or 96 h. From these results, we conclude that monocytes produce C5, C6, C7, C8 and C9 that assemble as the terminal complement complex on the surface of the agarose beads. Activation by agarose of the alternative pathway with generation of particle bound C3 and C5 convertases is a prerequisite for the subsequent formation of the terminal complement complex. Whether SC5b-9 or the membrane attack of complement (C5b-9) is formed on the beads will be examined.

Radioimmunoassay for immunoconglutinins

A competitive radioimmunoassay for immunoconglutinin (IK) was developed using isolated antostimulated rabbit IK labelled with 125I and glutaraldehyde-fixed sheep erythrocytes coated with fixed complement (EAC). IKs in test sera of human or animal origin produced specific inhibition of uptake of [125I]IK onto EAC and this was quantitated by reference to a calibration curve established with pure rabbit IK. Among 20 normal human sera the IK levels were: median 62 microgram/ml, range 41-170 microgram/ml and in 7 rat sera the levels were: median 71 microgram/ml, range 58-80 microgram/ml. Preliminary studies showed raised IK levels in the sera of patients with rheumatoid arthritis and with Crohn's disease.