When is a heterophile antibody not a heterophile antibody? When it is an antibody against a specific immunogen.

Heterophile antibodies are antibodies produced against poorly defined antigens. These are generally weak antibodies with multispecific activities. Human anti-animal antibodies that develop as a result of treatments with animal immunoglobulins are antibodies with strong avidities, produced against well-defined antigens. Although heterophile antibodies and human anti-animal antibodies interfere with immunological assays by similar mechanisms, modes for identifying the sources of the antibodies and for circumventing or retarding the interference may differ. Unfortunately, there has not been a well-organized attempt to encourage correct definition of these antibodies. This problem of inexact definition is highlighted by recent articles in this Journal. In the present discussion, we examine the history leading to this problem and discuss the origins and the reasons that the nature of the antibody is important for rectifying the problem. We propose a simple nomenclature for general usage that should appropriately characterize these antibodies in most cases. Copyright 1999 American Association for Clinical Chemistry.