Cytotoxic effect of serum on fibroblasts in one case of normolipidemic plane xanthoma and myeloma IgG lambda.

Serum was examined for a cytotoxic effect on cultured human fibroblasts, using 8 normal controls and 4 patients. Three of the patients had secondary lipidoses associated with monoclonal gammapathies of IgA kappa, IgG kappa and IgG lambda types. The fourth had systemic lupus erythematosus (SLE) with hyperlipidemia. Only serum containing the monoclonal IgG lambda was found to be cytotoxic. This circulating IgG lambda was strongly bound to HDL and behaved like an antilipoprotein antibody. The circulating immune complexes may be the serum factor responsible for the cytotoxicity and the cutaneous plane xanthomas, thus giving another example of 'antibody-dependent' cellular cytotoxicity previously described for endothelial cells in other diseases.