CYTOKINE REGULATION OF EARLY B-LYMPHOPOIESIS ASSESSED IN CULTURE

Lymphohemopoietic progenitors that are capable of expressing B-cell and myeloid lineages may be cultured from bone marrow cells of adult mice by using a two-step methylcellulose culture system, In this system, the primary colonies expressing myeloid lineages are plated in secondary culture for B-lymphoid colony formation, We have observed that combinations of two factors based on steel factor (SLF), such as SLF plus interleukin (IL)-6, SLF plus granulocyte colony-stimulating factor (G-CSF), and SLF plus IL-11 support the differentiation and proliferation of B-cell progenitors from the lymphohemopoietic progenitors, Surprisingly, IL-3 failed to support B lymphopoiesis either alone or in combination with other factors, In addition, when added to permissive culture conditions, IL-3 and IL-1 independently inhibited the B-cell potential of the primary colonies, The inhibitory effects of IL-3 and IL-1 observed in this in vitro system may be significant in the selection of cytokine combinations for in vitro expansion of hemopoietic stem cells.