Differentiation of normal marrow and HL60 cells induced by antithymocyte globulin.

Abstract

Antithymocyte globulin (ATG) therapy is an important treatment alternative for patients with acquired aplastic anemia. The mechanism by which it exerts its effects on hematopoiesis is unknown. In this report, we describe the ability of horse ATG to induce growth and differentiation of normal bone marrow. A single cell suspension of normal human bone marrow was cultured in methylcellulose medium and examined for the growth and maturation after incubation with ATG (10 pug/ml). After 3-4 days of culture, spherical colonies containing mature myeloid elements were found in cultures containing ATG but not in cultures containing medium or preimmunization horse IgG. The addition of 10% colonystimulating factor increased growth by 40%. The number of spherical colonies is not dependent on the presence of macrophages or T lymphocytes. This property of ATG may be relevant to the mechanism behind the hematologic recovery in some patients with acquired aplastic anemia. We also describe the ability of ATG to induce terminal differentiation in the HL60 leukemic cell line. ATG binds to HL60 cells and at concentrations between 10 and 100 pg/mi, 50% of the cells become mature granulocytes, acquire the ability to reduce nitroblue tetrazolium, and lose their proliferative capacity in the clonogenic assay. These new observations of ATG-induced differentiation of normal marrow myeloid elements and terminal differentiation of the HL60 cell line point to different avenues for future search of differentiation-inducing agents.

Antithymocyte globulin (ATG)-based therapy in patients with myelodysplastic syndromes

“…48,49 In addition to its immunosuppressive action, ATG has been shown to have direct effects on hematopoietic progenitor cells, in that it increases colony formation from primitive hematopoietic cells. [50][51][52] ATG restores hematopoiesis in many patients with aplastic anemia. 26,27,53 In a multicenter Table 3 Responses by diagnosis in 31 patients treated with ATG-cyclosporine and prednisone…”

Effects of antithymocyte globulin on bone marrow CD34+ cells in aplastic anaemia and myelodysplasia

“…Also, eliminating T‐suppressor cells with monoclonal T‐cell antibodies has not been shown to be effective in the treatment of AA ( Doney et al , 1985 ; Champlin et al , 1989 ). ATG has also been shown to be immunostimulatory as a result of its ability to induce the release of haemopoietic growth factors, resulting in in vitro colony stimulation ( Kawano et al , 1988 ; Taniguchi et al , 1990 ), and to have a direct effect on the proliferation and differentiation of HL 60 cells and normal haemopoietic progenitor cells ( Hunter et al , 1985 ; Huang et al , 1987 ).…”

Mechanisms of bone marrow progenitor cell apoptosis in aplastic anaemia and the effect of anti‐thymocyte globulin: examination of the role of the Fas–Fas‐L interaction

“…ATG rapidly results in profound lymphopenia that reverses in the following weeks (Genestier et al, 1998). In addition to its immunosuppressive action, ATG has been shown to have a direct effect on haemopoietic progenitor cells, inducing differentiation of HL60 cells to normal mature myeloid cells (Hunter et al, 1985) and increasing colony formation from normal primitive haemopoietic cells (CD34 1 , CD33 2 , CD38 2 , HLA DR low and lin 2 ), which is associated with downregulation of CD45RO expression (Huang & Mold, 1994). In AA, ATG has also been shown to stimulate granulocyte precursors (Faille et al, 1979) and colony formation from purified CD34 1 cells (Killick et al, 1998(Killick et al, , 2000.…”