Escherichia coli antibody: a screening test for immunodeficiency

Six patients suffering from recurrent chest infections were found to lack antibodies to a pooled antigen obtained from six different serotypes of commensal Escherichia coli bacteria. All had normal serum IgG concentrations, but five subsequently benefited from regular gammaglobulin injections. We suggest that the absence of such E. coli antibodies usually indicates a clinically significant defect in antibody production. This simple screening test is of use in the diagnosis of primary and secondary immunodeficiency disorders.