Stimulation of human bone marrow stromal cell tyrosine kinases and IL-6 production by contact with B lymphocytes.
The interaction of normal human B cell precursors with the bone marrow (BM) stromal cells that support their growth and maturation is mediated by adhesion of B cell CD49d/CD29 (alpha 4 beta 1 integrin or VLA-4) to stromal cell signal transduction, we generated CD49d-deficient variants of the RAMOS early b Burkitt's lymphoma cell line. RAMOS was chosen due to its lack of expression of CD49e (alpha 5 integrin) and CD44, which could potentially interact with stromal cells or their extracellular matrix. In contrast to the parental RAMOS cell line, CD49d-deficient RAMOS cell lines did not adhere to primary human BM stromal cells. Tyrosine phosphorylation of several stromal cell proteins was stimulated within 5 to 10 min of contact with either CD49d-expressing or CD49d-deficient RAMOS. These proteins included a 110-kDa substrate tentatively identified as pp125FAK. In contrast, mAb cross-linking of stromal cell CD106 had no significant effect on protein tyrosine phosphorylation. Il-6 production by stromal cells was enhanced up to fourfold over 3 days when stromal cells were cultured in contact with RAMOS cells, regardless of CD49d expression. Stromal cell IL-6 production was not significantly enhanced by RAMOS cells cultured above the stromal cells in Transwell inserts. Thus, we have demonstrated through the use of paired CD49d-expressing and CD49d-deficient RAMOS cell lines that protein tyrosine kinase activity and IL-6 production by primary human BM stromal cells can be enhanced in a manner that is dependent on B cell contact but independent of CD49d-mediated adhesion. These results indicate the potential for B cells to interact with cells in their microenvironment and activate feedback mechanisms mediated by stromal cells, which may regulate lymphopoiesis.
Jarvis
L J
LJ
Department of Laboratory Medicine and Pathology, University of Minnesota Medical School, Minneapolis 55455, USA.
LeBien
T W
TW
D000911:Antibodies, Monoclonal / Q000276:immunology; D015703:Antigens, CD / Q000502:physiology; D001402:B-Lymphocytes / Q000378:metabolism*; D001853:Bone Marrow / Q000201:enzymology* / Q000378:metabolism; D002448:Cell Adhesion / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000276:immunology; D003429:Cross Reactions / Q000276:immunology; D004790:Enzyme Induction; D006801:Humans; D039441:Integrin alpha4; D015850:Interleukin-6 / Q000096:biosynthesis*; D011505:Protein-Tyrosine Kinases / Q000096:biosynthesis*; D017154:Stromal Cells / Q000201:enzymology* / Q000378:metabolism; D014407:Tumor Cells, Cultured; D019010:Vascular Cell Adhesion Molecule-1
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D015815:Cell Adhesion Molecules; D015850:Interleukin-6; D019010:Vascular Cell Adhesion Molecule-1; D039441:Integrin alpha4; D011505:Protein-Tyrosine Kinases