Figure 4. Avidity index for antibodies induced in animals immunized with mouse serum albumin (MSA) carrying 3 or 15 2-hydroxyethylmethacrylate (HEMA) molecules, respectively. Serum was diluted, on average, 1:5000 for MSAH3 and 1:2000 for MSAH15 to yield a similar antibody activity. Wells were incubated with potassium thiocyanate (KSCN) at different concentrations, ranging from 0.1 to 3.2 M, in duplicate. Triplicate wells were incubated with PBS so that maximal activity could be assessed. The avidity is expressed as the KSCN concentration where 50% of the antibody activity is eluted compared with the activity in wells incubated with innocuous PBS. Each group consisted of 8 animals. One animal was omitted from the MSAH15 group, due to low anti-MSA antibody activity. Each dot represents 1 mouse, and the horizontal bars indicate median values. The Mann Whitney U-test was used in statistical comparison.