A B-cell proliferation with aberrant true E-rosette formation: a sequential study with a panel of monoclonal antibodies and other surface markers.

A case of B-CLL in prolymphocytic transformation is described in which large numbers of peripheral blood mononuclear cells possess surface immunoglobulin and rosetted with AET-treated sheep erythrocytes (SIg+E+), but lacked specific T-cell antigens. The SIg (MDGK) was shown to be an intrinsic product of the cell, whose B-cell nature was confirmed by staining with BA1, a specific anti-B-cell monoclonal antibody. The E positivity resembled the rosetting of normal T cells in certain important respects but was weak, and aberrant in certain other respects. Although E rosetting was blocked with anti-chi and anti-D but not with anti-lambda, extensive blocking studies with a panel of monoclonal antibodies indicated that this was due to steric hindrance of weak E receptor rather than specific blocking of SIg possessing anti-E activity. The case is compared and contrasted with previous rare examples of SIg+E+ proliferations and briefly discussed in relation to the recent demonstration that certain non-T cells can express E receptor in vitro.