Production of specific cell types has to be induced when new cells are required and has to stop when sufficient cells have been produced. This requires an appropriate balance between inducers and inhibitors of development. The network of interactions between hematopoietic cytokines (Fig. 2) thus includes cytokines that can function as inhibitors of hematopoietic cell multiplication such as TNF. Another inhibitory cytokine, type (β1 transforming growth factor (TGF-,B1), which is part of this network (42) can selectively inhibit the activity and the production of some CSFs and ILs (44). Other cytokines
which may also participate in the network include interferons α/ β and g and IL-4, IL-10, and IL-13. These cytokines can exert negative effects on the responsiveness of
hematopoietic myeloid cells to certain CSFs and on the production of these cytokines (45-47).