Autoantibody against a 58 kD molecule in a patient with neutropenia and NK cell deficiency

A patient with Evans' syndrome is described who developed intermittently an immunocytopenia consisting of autoimmune neutropenia and natural killer (NK) cell deficiency. During this time an autoantibody binding to a 58 kD antigen expressed on granulocytes, activated NK cells and Epstein-Barr virus (EBV) transformed B cells was present. Incubation of activated NK cells and NK cell clones with the autoantibody leads to a significant inhibition of NK activity. Therefore the autoantibody may detect a functionally important activation molecule.