Intracytoplasmic localization of CD3 antigen in NKH1+ azurophilic granular T-lymphoblastic lymphoma cells

The intracytoplasmic localization of CD3 antigen was examined in azurophilic granular T-lymphoblastic lymphoma cells obtained from a 27-year-old female. Examination by flow cytometry and an immunohistological method revealed that the surface phenotype of the lymphoma cells were NKH1+, CD5+, CD7+, CD1-, CD2-, CD4-, CD8- and CD16-. CD3 was not detected on the cell-surface by flow cytometry but was found in the cytoplasm using the immunohistological method. CD3 was detected in the perinuclear space and rough endoplasmic reticulum (rough ER) by an immunoelectron microscopic study. An electron microscopic observation of the granules revealed lysosomal structures with low electron density. The lymphoma cells proliferated when cultured in the presence of interleukin-2 but showed no NK (K562) activity before and after culture. The molecular size of metabolically labeled intracytoplasmic CD3 precipitated by Leu 4 monoclonal antibody was identical to that of normal CD3. These results indicate that the lymphoma cells are neoplastic counterparts of immature thymocyte at a very early stage of differentiation and may be related to the lineage of CD3+ NKH1+ T-lymphocyte.