The effects of IL-1 beta and IL-4 on the proliferation and endogenous secretion of growth factors by acute myeloblastic leukemic cells.

The effects of interleukin-1 beta (IL-1) and IL-4 were studied on the proliferation of acute myeloid leukemia (AML) cells. IL-1 stimulated tritiated thymidine (3H-TdR) uptake of AML cells in 8/12 cases, whereas IL-4 enhanced 3H-TdR uptake in 5/12. Combination of both factors resulted in an additive effect in 6/12 cases which could be abrogated by the addition of anti-granulocyte-macrophage colony stimulating factor (GM-CSF). To study whether IL-1, IL-4, or IL-1 plus IL-4 affects the AML progenitor cell directly or indirectly by the release of endogenous factors, supernatants of stimulated AML cells (n = 6) were analyzed for GM-CSF, IL-6, and tumor necrosis factor-alpha (TNF) production. IL-1 induced the endogenous secretion of GM-CSF, IL-6, and TNF in most cases. In contrast, no secretion of growth factors was induced by IL-4, whereas in 2 cases IL-4 suppressed the IL-1-induced secretion of GM-CSF, TNF, and IL-6. This was associated with a decline in the proliferative response to IL-1 measured in a clonogenic assay. In addition it was shown that exogenous supplied GM-CSF and TNF could raise the suppressive effects of IL-4 on the IL-1-supported proliferation. In summary these data indicate that the IL-4-supported proliferation is not caused by the endogenous secretion of GM-CSF, IL-6, and TNF. Furthermore the suppressive effect of IL-4 on the IL-1-induced proliferation in some cases may be caused by a reduced secretion of GM-CSF, TNF, and IL-6.

Expression and regulation of IL-4 receptors on human monocytes and acute myeloblastic leukemic cells.

Evidence is presented that human monocytes and acute myeloblastic leukemic (AML) cells contain both high and low affinity binding sites for interleukin-4 (IL-4). On monocytes 183 +/- 132 high affinity binding sites per cell with a Kd of 60 +/- 29 pM and 1500 +/- 600 low affinity receptors with a Kd of 2.3 +/- 0.4 nM (X +/- S.D., n = 6) could be demonstrated. On AML cells (n = 11) a comparable number and binding affinity of IL-4 receptors were observed (77 +/- 36 high affinity receptors with Kd 72 +/- 31 pM and 2400 +/- 1000 low affinity receptors with Kd of 2.2 +/- 0.7 nM). In addition, no cross-competition was shown between radiolabeled IL-4 and IL-1-alpha, IL-3, IL-6, IL-7, G-CSF, and GM-CSF. Both types of receptors on monocytes as well as on leukemic blasts could be down-modulated in a similar fashion by IL-4 and activators of protein kinase C (PKC), but not by the calcium ionophore A23187. The down-modulation by PKC activators was caused by an increased internalization, degradation and release of radiolabeled IL-4 in the medium. Finally, the functionality of the IL-4 receptors were tested on AML cells with a 3H-thymidine proliferation assay. In 8/11 cases IL-4 affected AML proliferation. These data demonstrate two different binding sites for IL-4 on normal and leukemic cells, which can be modulated by external activation signals in an analogous way.