Samples of test or control serum (15 Rl) were placed in the peripheral wells, and 10 RI of protoplasmic antigen (10 mg/ml; Allied Laboratories Inc.) was placed in the central well. Plates were read for precipitation bands of identity at 48 h (14). Enzyme-linked immunosorbent assay (ELISA) testing was done with the L-arabinomannan antigen (17). Flatbottomed 96-well microtitration plates (Nunc, Roskilde, Denmark) were coated with 0.2 ml of L-arabinomannan antigen per well (0.5 ,ug/ml in 0.1 M carbonate-bicarbonate buffer, pH 9.6; provided by E. A. Sugden, Agriculture Canada, Animal Disease Research Institute, Nepean, Ontario, Canada).