Demonstration of intracytoplasmic immunoglobulin in non-T-acute lymphocytic leukemia cases of children with immunoelectron microscopic examination.

Leukemic cells from 25 cases of non-T-acute lymphocytic leukemia (ALL) in children were investigated for intracellular immunoglobulin by the use of immunoelectron microscopic study (immuno-EM). As a result, 12 cases were negative for both heavy and light chains of the immunoglobulin in the neoplastic cells. Of these, one case that was also negative for common ALL antigen (CALLA) was defined as null cell type. The remaining 11 cases were defined as common ALL type. Six cases were defined as pre-B-cell type because they were positive for cytoplasmic mu chain but negative for cytoplasmic light chains. Seven cases were defined as B-cell type, all of which possessed lambda light chains in the neoplastic cells. Immunohistologic studies using monoclonal antibodies showed that most non-T-ALL cases were positive for CALLA and B4, whereas about 50% of them were positive for B1. Our immuno-EM study suggests that it is one of the effective ways of subclassifying non-T-ALL in children.