Thirty-one patients with W.M. were studied and the results confirmed
our previous data.’5 Intracytoplasmic staining for monoclonal 1gM was
restricted to the bone marrow plasma cells and to a limited number of bone
marrow and blood lymphocytes (except for a single case where 30% of
lymphocytes contained detectable intracytoplasmic 1gM). However most bone
marrow proliferating lymphoid cells, including plasma cells, and 10%-80%
(mean 50%) of blood lymphocytes from untreated patients exhibited a surface
1gM with the same light-chain type as the serum 1gM. When the
proliferation was controlled by therapy, a low percentage of blood lymphocytes
(mean 9%) carried the monoclonal 5.1gM. The fluorescence pattern
was strinkingly heterogeneous in every patient. Control experiments ruled
out the possibility of a passive coating of serum 1gM on the lymphocytes
and proved the actual synthesis of 5.1gM by the cells.