MedB-1, a human tumor cell line derived from a primary mediastinal large B-cell lymphoma.

Primary mediastinal B-cell lymphoma is a locally highly aggressive but poorly disseminating tumor composed of medium sized or large cells most probably of thymic medullary origin. It has a mature B-cell phenotype, typically lacks immunoglobulin expression and has variable defects in expression of HLA-molecules. We present here a cell line, MedB-1, derived from such a tumor. As is frequently found in mediastinal B-cell lymphomas in situ, MedB-1 is CD10(-), CD19(+), CD21(-), CD22(+), CD23(+), CD25(-), CD37(+), CD38(-), CD39(+), CD40(+), CD54(+), CD95(+). Like the parental tumor, MedB-1 lacks HLA-A,B,C alpha-chains and beta(2)microglobulin and expresses HLA-D molecules at decreased levels. Both parental tumor and MedB-1 cells are clonally related as shown by immunoglobulin heavy chain gene rearrangement analysis. Unlike the parental tumor tissue, the MedB-1 cell line cytoplasmically expresses IgG/kappa in a very small subset of cells under standard culture conditions. MedB-1 does not contain any Epstein-Barr virus DNA. In a tissue adhesion assay MedB-1 cells showed an extensive binding to the medullary region of normal thymus. Altogether, MedB-1 is a suitable tool for functional and molecular analysis of this distinct lymphoma entity.