A sandwich immunoassay to quantify low levels of turbot (Scophthalmus maximus) immunoglobulins

We have developed an enzyme-linked immunosorbent assay for the quantification of turbot (Scophthalmus maximus) immunoglobulin (Ig). The capture antibody is a rabbit polyclonal antiserum to turbot Ig, and the detector antibody a monoclonal antibody (UR3) to the turbot Ig heavy chain. Both antibodies bind nearly 100% of turbot Ig. The assay allows detection of turbot Ig in serum at concentrations as low as 0.16 μg ml−1 and takes less than 4 h. Precision is satisfactory, with intra-assay coefficients of variation (CVs) ranging from 2.1 to 16.6%, and inter-assay CVs ranging from 5.8 to 24.6%. We used the assay to determine Ig concentrations in the sera of healthy turbot of different weights. Mean serum Ig concentration was 3.35 ± 0.74 mg ml−1 for fish weighing 15–25 g and 11.14 ± 1.87 mg ml−1 for fish weighing 1000–2000 g.