MYELOMA BONE-MARROW PLASMA-CELLS - EVIDENCE FOR THEIR CAPACITY AS ANTIGEN-PRESENTING CELLS

Myeloma plasma cells constitute 10%. to 90% of the fetal bone marrow c ell count in patients with multiple myeloma [MM). These cells express a variety of cell surface markers, such as HLA-ABC and HLA-DR, and sur face antigens that are necessary for professional antigen-presenting c ells, including adhesion and costimulatory molecules. In this study, w e examined the expression of major histocompatability complex (MHC) an d costimulatory molecules on CD38((bright,++)) plasma cells in bone ma rrow aspirates from eight MM patients. Small percentages of plasma cel ls expressed weak but detectable levels of HLA-DR, HLA-DO, CD40, CD80, and CD86, which could be upregulated by interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha, CD38(++) plasma cell and CD3(8(dim,+) ) cells were sorted from freshly isolated hone marrow mononuclear cell s and tested for their capacity to act as antigen-presenting cells, In deed, both CD38(++) plasma cells and CD38(+) cells were able to stimul ate allogeneic T cells and present the soluble antigens purified prote in derivative and tetanus toroid to autologous T cells, Recognition of the antigens led to T-cell proliferation and secretion of IFN-gamma a nd was MHC class-I and -II restricted. Antigen processing and presenta tion by CD38(++) and CD38(+) cells were abolished by treatment of the cells with chloroquine, Hence, our study provides for the first time e vidence that myeloma plasma cells may act as antigen-presenting cells, Further studies are warranted to examine in detail the molecules requ ired for inducing T-cell stimulation, (C) 1997 by The American Society of Hematology.