The gamma globulin fractionated by the Tiselius electrophoretic technic from the plasma of patients with acute disseminated lupus erythematosus was used as an antigen to induce antibodies in rabbits. Similarly, antibodies were induced in control rabbits with normal human serum and with normal human gamma globulin.

The antisera developed in these three groups of rabbits were added to the L. E. gamma globulin solution and, after precipitation, the supernatant fluid was added to bone marrow preparations.

The L. E. phenomenon was not demonstrable after the L. E. gamma globulin was precipitated by anti-L. E. gamma globulin rabbit serum. However, after precipitation of the L. E. gamma globulin by anti-normal human serum rabbit serum, or by anti-normal human gamma globulin rabbit serum, the L. E. phenomenon was still apparent.

These studies suggest that the L. E. factor is an immunologically distinct component of L. E. gamma globulin.

ACKNOWLEDGMENTS We wish to thank Miss Mary Stepien and Miss Alice Gates for their valuable technical help.