Predominant expression of lambda light chain in adult cases with non-T-cell acute lymphocytic and chronic myelogenous leukemia in lymphoid blast crisis.

The authors investigated cytoplasmic immunoglobulins of the leukemic cells from 20 adult cases with non-T-cell acute lymphocytic leukemia (ALL) and from three cases with chronic myelogenous leukemia in lymphoid blast crisis using immunoelectron microscopy. They also studied these cases using various monoclonal antibodies. Of the 23 examined cases, nine were negative for both heavy and light chains of immunoglobulins; the authors defined these as common ALL. Two cases were positive for the mu chain but were negative for light chains; the authors defined these as pre-B-cell ALL. The remaining 12 cases were positive for either kappa or lambda light chains; these were defined as B-cell ALL. Of the 12 cases positive for light chains, 11 were positive for the lambda chain. Seven cases of the 11 positive cases for the lambda chain were negative for heavy chains. Eleven cases were positive either for both My4 and My9 or for one of the two antibodies. From these results, the authors conclude the following: (1) the ratio of pre-B-cell ALL among non-T-cell ALL cases (two of 23 cases) was lower in adults than in children; (2) of the light chain-positive cases, the lambda light chain-positive cases predominated (11 of 12 cases); (3) heavy chain-negative, lambda chain-positive cases (seven cases) were observed; and (4) one half of the leukemia cases showed dual phenotypes of B-cell and myeloid cell lineages.