Abstract
The cross reactivity of a well-characterized PBC serum was studied with mitochondria from a number of sources. These studies were to establish the nonorgan, species specificity of the reaction of PBC sera. As well as confirming some previously reported data, we have strong evidence suggesting that, in spite of species differences inM r of the major antigenic bands, all mitochondria contain a set of common cross-reactive epitopes. The multiplicity of antigenic bands seen for mitochondria from some sources are shown to arise, in part, as proteolytically derived artefacts of bands of higherM r , retaining some antigenic reactivity.