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.