The importance of antibody quality in sandwich ELISA systems. Evaluation of selected commercial reagents.

The detection of low levels of immunoglobulin in cell culture supernatants etc. by ELISA procedures demands high sensitivity and absolute specificity. We have used commercially available antibodies prepared by positive affinity purification and immunoglobulin fractions obtained by ion-exchange chromatography in various combinations in ELISA systems for such quantitative analyses. These demonstrate that when affinity-purified reagents lacking unwanted anti-species cross-reactivity are used as both the capture antibody and the indicator antibody the results are markedly superior (high sensitivity, low backgrounds and a wide working range) compared to those obtained with all other possible combinations.