al., 1974). In the present study, normal skin from 57 adults was examined for the standard IgG, IgA, IgM, and C3; in addition, 37 cases were examined for other complement stages (Clq and C4), properdin, transferrin, and IgD. Clq and C4 are found only in classical complement activation, whereas C3 (the main amplification step) is found in both classical and alternate pathway activation; properdin forms part of the activation sequence for the alternate pathway and is usually considered to indicate involvement of the alternate pathway-which, however, is also activated by a feedback loop in the classical pathway (Roitt, 1977); properdin has been described in affected and unaffected skin of patients with systemic lupus erythematosus (Schrager and Rothfield, 1976;Schroeter et al., 1976). Transferrin indicates nonspecific leakage of protein through vessel walls as it is neither an immunoglobulin nor involved in the