ASSESSMENT OF INTRACELLULAR TAP-1 AND TAP-2 IN CONJUNCTION WITH SURFACE MHC CLASS-I IN PLASMA-CELLS FROM PATIENTS WITH MULTIPLE-MYELOMA

Immunotherapy involving cytotoxic T lymphocytes (c-ms) is an attractiv e alternative for treatment of various malignancies, including multipl e myeloma. For tumour cells to be recognized and killed by CTLs they m ust express cell surface major histocompatibility complex (MHC) class I molecules and the transporter associated with antigen processing (TA P). However, loss of MHC class I and the TAP protein are common among several types of solid tumours, This study assessed the expression of TAP protein (by intracellular flow cytometry) and cell surface MHC cla ss I molecules in three human myeloma cell lines as well as the plasma cell population (CD38(+) bright) in bone marrow specimens from 13 mul tiple myeloma patients. In all of the patients, 100% of the plasma cel l population expressed both the TAP subunits and cell surface MHC clas s I molecules, but at varying intensities. Both TAP and MHC class I we re also expressed in the three myeloma lines, Additionally, the functi on of the antigen transport machinery was evaluated by a peptide trans porter assay in the three myeloma lines. TAP transporter activity was readily detectable in two out of three myeloma lines, whereas the dimi nished activity in the third cell line was completely restored by co-c ulturing with recombinant interferon-gamma (rIFN-gamma).