Expression of Granulysin mRNA in the Human Megakaryoblastic Leukemia Cell Line CMK

Granulysin is a newly reported cytolytic molecule and colocalizes with perforin and granzymes in the granules of cytotoxic T lymphocytes (CTL) and natural killer (NK) cells. In this study, we found that the megakaryoblastic leukemia cell line CMK, established from a patient with Down’s syndrome, expressed granulysin mRNA. CMK was positive for CD13 and CD41 and negative for CD56. CMK also expressed CD2 and CD7. However, no rearrangement of the T-cell receptor β-chain gene, an early marker of T-cell lineage, was found in CMK cells. Thus, CMK is assumed to originate from the clonal evolution at the immature cell level. The expression of granulysin in CMK cells suggests that granulysin is occasionally present in immature multilineage cells or may be characteristic of leukemic cells obtained from Down’s syndrome patients. CMK has been reported to be capable of differentiating to mature megakaryocytes and produce platelets with normal function. It therefore seems to be possible that granulysin is also present in normal platelets. Unfortunately, we were not able to obtain evidence that normal platelets contain granulysin mRNA and its antigen.