FIG. 1.

Visual definition of agglutination reactions. (A) Agglutination reactions photographed while still wet with CPS in solution. Agglutination activity is defined from +++ (uppermost reaction) to − (lower reaction). (B) Agglutination reactions photographed after drying by using pure CPS solution in PBS serially diluted from 120 to 0 ng of CPS ml⁻¹. The clarity of the agglutination reaction is reduced upon desiccation, while at 1.9 and 0.9 ng ml⁻¹ reactions that were still wet were positive, although this is not apparent in the figure.