False spurs in quantitative immunoelectrophoresis.

Antigens which show reactions of identity in double-diffusion tests in gel may cause spur formation in crossed immunoelectrophoretic techniques. To differentiate these misleading spurs from spurs of double-diffusion tests which show the true immunochemical relationship between antigens, we have denoted the former type "false spurs". False spurs are often formed in tandemcrossed immunoelectrophoresis and fused rocket immunoelectrophoresis when antigens with different electrophoretic mobility are compared. On the basis of model experiments, criteria are set up for accepting a spur as a true spur, and procedures are described for avoiding formation of false spurs in quantitative immunoelectrophoresis.