Immunological and biochemical characteristics of acid citrate eluates from tumour cells: a major non-immunoglobulin component.

Using competitive double-antibody radioimmunoassays we have shown that immunoglobulin (especially IgA) can be recovered in pH 3.5, 0.12M acid citrate eluates of freshly excised CCH1 tumour-cell suspensions. Studies with 125I-labelled eluates indicate that such preparations exhibit a variable, but appreciable, degree of non-specific binding to unrelated syngeneic tumour and normal tissues. PAGE/SDS gel electrophoresis of the labelled eluates revealed the presence of a major non-immunoglobulin component of 33-36K dalton which could account in part for the non-specific binding observed. This component was also detected in similar eluates from cultured CCH1 tumour and in all other tumour-cell eluates examined to date. In contrast, preliminary data suggest that it is less prevalent in acid citrate eluates from normal tissue, with the exception of peritoneal-exudate cells. The possible origins, nature and significance of this non-immunoglobulin component are discussed.