Selective expression and function of granzyme D in lymphohematopoietic stromal cells

Granzymes are a family of serine proteases exclusively detected in the granules of cytotoxic lymphocytes, and in mice at least eight granzymes, A to G and K, have been identified. Except for granzymes A and B, which activate the apoptotic pathway, little is known about the exact functions of the other granzymes. We have found that the granzyme D transcript is selectively expressed in functional hematopoietic stromal lines as well as primary stromal cells. Stromal lines supported growth of a pre-T lymphoma clone BTK at an efficiency proportional to the expression level of granzyme D, while a stromal line lacking granzyme D failed to do so. When the defective stromal line was transfected with granzyme D cDNA, it could efficiently support the growth of BTK cells. The results indicate that granzyme D expressed in the stromal cells plays an important role in stromal cell-lymphocyte interaction.