REGULATION OF LIPOPOLYSACCHARIDE-INDUCED GRANULOPOIESIS AND MACROPHAGE FORMATION BY SPLEEN-CELLS .1. RELATIONSHIP BETWEEN COLONY-STIMULATING FACTOR RELEASE AND LYMPHOCYTE-ACTIVATION INVITRO

Abstract

Addition of [Escherichia coli] lipopolysaccharide (LPS), a B [bone marrow-derived] cell mitogen, to mouse spleen cultures strongly stimulated production of colony-stimulating factor (CSF), the humoral regulator of granulopoiesis, and macrophage formation in vitro. Secretion of CSF from LPS-stimulated spleen cells coincided with cellular DNA synthesis and cell transformation; both activities could be attributed to the lipid A moiety of the molecule. Different experimental approaches were used to study the relationship of CSF release and lymphocyte activation in response to LPS. Modification of LPS with polymyxin B, a bactericidal antibiotic for most Gram-negative bacteria, caused a marked reduction in mitogenic activity, although the ability to induce CSF was not significantly altered. Spleen cells from CBA/N mice, a mutant strain with an x-linked genetic defect in immunologic and mitogenic responses to polyclonal activators including LPS, showed diminished mitogenic responses; however, high levels of CSF were produced. Mitotic and DNA inhibitors (colchicine and cytosine arabinoside) did not affect CSF release although they completely inhibited mitogenicity. The spleen cell population participating in the process of LPS-induced CSF generation is probably a nondividing, terminally differentiated one without need for DNA synthesis. Active RNA and protein synthesis are needed in this process.