GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR-RECEPTOR - STAGE-SPECIFIC EXPRESSION AND FUNCTION ON LATE B-CELLS

Granulocyte-macrophage colony-stimulating factor (GM-CSF) receptors (G MR) are expressed on myeloid cells throughout their maturational seque nce, During myelopoiesis, GM-CSF induces the proliferation of precurso rs and has multiple effects on more mature cells; such effects include induction of maturation and priming for subsequent stimulation. GMR i s expressed on a range of other cell types including acute leukemic bl asts of myeloid and lymphoid lineage, but has been little studied on m ore mature lymphoid cells. Using sensitive triple-layer immunophenotyp ic techniques, we show here that both the alpha and beta(c) chains of the GMR are expressed on hairy cells (HCs) and myelomatous plasma cell s (PCs), but not on chronic lymphocytic leukemia (CLL) or prolymphocyt ic leukemia (PLL) lymphocytes. The receptor was demonstrable on normal PCs in tonsil, but not on either activated or resting tonsillar B cel ls or on circulating normal B lymphocytes. The expression of the recep tor is therefore stage specific, rather than a feature of activation. Perhaps, surprisingly, in view of its effects on myeloid cells, GM-CSF did not stimulate the proliferation or differentiation of HCs and did not protect them from apoptosis. However, the cytokine had a profound effect on the interaction of the HC with its environment. Thus, the c ytokine caused a major cytoskeletal reorganization resulting in the in hibition of motility and loss of adhesion to cellular and matrix ligan ds, These studies indicate the importance of GM-CSF outside myelopoies is and demonstrate a previously unrecognized stage specific role for t he cytokine in B-cell biology. Taken together with our previous report that M-CSF enhances B-cell motility, the present findings indicate th at myeloid growth factors act in concert to facilitate the controlled migration of certain B cells into and within tissues. (C) 1996 by The American Society of Hematology.