Presence of matrix-specific antibodies in affinity-purified polyclonal antibodies

In general, antigen affinity columns made with commercially prepared activated affinity supports bind antibody specific for the coupled antigen. Nonetheless, in some cases affinity purification may yield antibodies to molecules other than the molecule of interest. In this report, we demonstrate such an occurrence: an antibody which adsorbs to an Affi-Prep 10 affinity matrix was found in the serum of sheep immunized against calmodulin. The contaminating antibody bound to cell nuclei and condensed chromosomes; the composition of the Affi-Prep 10 matrix suggests that the antibody may cross-react to the sugar-phosphate backbone of DNA. We were able to remove the contaminating antibody from the anti-calmodulin by passing the affinity-purified mixture over an antigen-free Affi-Prep 10 column.