Engulfed cell remnants, and not cells undergoing apoptosis, constitute the LE-cell phenomenon.

The LE cell has been one of the first immunological signs of active systemic lupus erythematosus, included into the ACR criteria. LE cells consist of a phagocyte engulfing material of disputed origin, which was interpreted as either cellular remnants from necrotic cells or as early apoptotic cells. It is well established that LE cell formation is dependent on autoantibodies against the linker histone H1. In view of this fact, we investigated whether anti-histone H1 antibodies and LE cell positive sera bound to cells where apoptosis had been induced by gliotoxin or actinomycin D or which were necrotic after heating. Necrotic cell remnants, but not (early) apoptotic cells were bound by anti-histone H1 antibodies and LE cell positive sera, establishing that the process of LE cell formation, which is dependent on anti-H1 binding, leads to engulfment of necrotic (or late apoptotic) material, but not of early apoptotic cells.