Cytokine regulation of the myeloid glycoprotein CD14

Monocyte membrane CD14 (mCD14) antigen expression was measured in normal human monocytes and blood monocyte-derived macrophages. Seven-day culture of monocytes in serum-containing medium lead to an increase in mCD14. Addition of interferon-gamma (IFN gamma) or interleukin-4 (IL-4) to monocytes caused a dose-dependent reduction in mCD14 within 3 or 45 h respectively. These effects were strong in monocytes, weak in macrophages, and they were blocked by anti-IFN gamma and anti-IL-4 antibodies, respectively. Interleukin-2 and interferon-alpha produced a decrease in mCD14 in mononuclear leukocyte cultures but not in purified monocytes. Their effect was abolished in the presence of anti-IFN gamma. Other cytokines (TFN alpha, Ill beta, IL-6, IL-3, IL-5, GM-CSF, TGF beta 1) did not change mCD14. In conclusion, IFN gamma and IL-4 are revealed to be the only cytokines which directly affect monocyte CD14 expression.

Priming the macrophage respiratory burst with IL-4: enhancement with TNF-alpha but inhibition by IFN-gamma

Pre-exposure to bacterial lipopolysaccharide (LPS) or certain cytokines is known to enhance the ability of murine macrophages to generate a respiratory burst in response to subsequent stimulation, a phenomenon referred to as 'priming'. We report here that the cytokine interleukin-4 (IL-4) can prime murine macrophages. Pretreatment of murine bone marrow-derived macrophages (BMM) with 10 U/ml murine IL-4 for 48 hr was found to enhance the respiratory burst following subsequent stimulation with phorbol myristate acetate (PMA) (10(-6) M) or zymosan (1 mg/ml). Human tumour necrosis factor-alpha (TNF-alpha) (10(-9) M) can also prime BMM for an enhanced respiratory burst and the combination of TNF-alpha and IL-4 resulted in an enhanced (greater than additive) priming effect. In contrast, interferon-gamma (IFN-gamma) (100 U/ml), although by itself capable of priming the BMM respiratory burst, was found to antagonize the priming effects of IL-4. These results demonstrate that IL-4 can be added to the growing list of cytokines capable of modulating the respiratory burst response of macrophages, suggesting a possible role for this cytokine in inflammation and in the host response to infection. The opposing effects of TNF-alpha and IFN-gamma when interacting with IL-4 highlight the difficulties in predicting the effect of a given cytokine in vivo, where potential interactions with other cytokines must be considered.

B-cell growth factor-induced and alpha-interferon-inhibited proliferation of hairy cells coincides with modulation of cell surface antigens

alpha-Interferon (IFN-alpha) induced unique ultrastructural alterations in peripheral blood and splenic hairy cell leukemia (HCL) cells (14 of 20 cases) treated in vitro. To further investigate the effects of B-cell growth factor (BCGF) and IFN-alpha on target hairy cells (HCs), we utilized immunogold labeling in conjunction with scanning electron microscopy. This methodology, in contrast to other immunological methods, facilitated direct view of the expression, density, and rearrangement of selected antigens/receptors on individual cells before and after BCGF or IFN-alpha treatment. In addition to inducing proliferation of HCL cells, BCGF enhanced the expression of interleukin 2 receptors (CD25; T-activated cell antigen) with no change in the expression of class I and class II human leukocyte antigen. On the other hand, IFN-alpha did not exert a noticeable proliferative effect on HCL cells but rather inhibited the proliferation of BCGF-treated cells. In addition, IFN-alpha treatment revealed an enhanced expression of class I (4 of 9) and class II (12 of 15) human leukocyte antigen on target HCs. Two-day exposure of HCs to IFN-alpha resulted in enhanced expression of CD25 (11 of 14), whereas a decrease in CD25 expression was recorded in 4 of 5 cases treated with IFN-alpha for 3 days. Also, no significant change in the expression of two other HCL-related surface antigens, CD22 (S-HCL-1; Leu-14) and CD11c(S-HCL-3; Leu-M5), was recorded following up to 3 days of IFN-alpha or BCGF treatment. However, a 5-day exposure to IFN-alpha resulted in a significant decrease in expression of CD11c on treated HCs. Finally, the IFN-alpha-induced immunoultrastructural changes in target HCs were primarily encountered in cells from HCL cases classified as responders to in vivo IFN-alpha therapy. Our data add support to the concept that the effect of IFN-alpha in HCL is mediated by impairment of the response to B-cell growth factors and induction of further differentiation of the target cells.

A soluble, high-affinity, interleukin-4-binding protein is present in the biological fluids of mice

Cytokines such as interleukin 4 (IL-4) play a key role in the regulation of immune responses, but little is known about how their multiple activities are regulated in vivo. In this report, we demonstrated that an IL-4-binding protein (IL-4BP) is constitutively present in the biological fluids of mice (serum, ascites, fluid, and urine). Binding of 125I-labeled IL-4 to the IL-4BP is specific and saturable and can be inhibited by an excess of unlabeled IL-4 but not IL-2. The IL-4BP binds IL-4 with an affinity similar to that reported for the cellular IL-4 receptor (Kd approximately 7 x 10(-11) M) and has a molecular mass of 30-40 kDa and pI values of 3.6-4.8. IL-4BP-containing biological fluids or purified IL-4BP competitively inhibit the binding of 125I-labeled IL-4 to mouse T or B cells and inhibit the biological activity of IL-4 but not IL-2. The serum levels of IL-4BP in severe combined immunodeficiency (SCID) mice are lower than those of normal mice. The above findings suggest that IL-4BP plays an important immunoregulatory role in vivo.

Influence of interleukin-4 and platelet-activating factor on the Fc epsilon RII/CD23 expression on human monocytes

Human recombinant interleukin-4 (IL-4) induces the expression of the low-affinity receptor for IgE (Fc epsilon RII/CD23) on human normal monocytes as assessed by flow cytometry. Also, platelet-activating factor (PAF) induces a time- and dose-dependent increase in Fc epsilon RII/CD23 expression, which is maximal with 1 microM PAF and after a 24-h incubation period. Under similar experimental conditions, lyso-PAF (1 microM) has no effect on Fc epsilon RII/CD23 expression. The PAF-induced Fc epsilon RII/CD23 expression on human monocytes is inhibited by two unrelated antagonists of the mediator, namely BN 52021 and BN 50730, but is not significantly affected when the cells are incubated in the presence of a rabbit anti-IL-4 antiserum. The IL-4-induced Fc epsilon RII/CD23 is abolished in the presence of the anti-IL-4 antiserum and slightly (not significantly) reduced when BN 52021 or BN 50730 is added to the incubation medium. These results suggest that PAF regulates Fc epsilon RII/CD23 expression and may indicate a new role for this autacoid in allergic diseases.

Distinct mechanisms of suppression of murine T cell activation by the related macrolides FK-506 and rapamycin

FK-506 and the structurally related macrolide rapamycin (RAP) were investigated in comparison with cyclosporin A (CsA) for their immunosuppressive effects on murine T cells. All three agents suppressed the proliferation of splenic T cells triggered by lectins or antibodies to CD3 and Ly-6C. FK-506 or CsA also inhibited proliferation, IL-2 production, and IL-2R expression in splenic T cells activated with ionomycin + PMA. However, RAP minimally affected IL-2 production and IL-2R expression in these cells, although it reduced proliferation. Similarly, FK-506 and CsA, but not RAP, suppressed IL-2 production by activated DO.11.10 T hybridoma cells. In such a system, as well as in normal T cells stimulated with high ionomycin concentrations, FK-506 and CsA enhanced proliferation, indicating that they both abrogate negative signals associated with T cell activation. On the contrary, RAP diminished the autonomous proliferation of hybridoma cells, whereas FK-506 and CsA had little effect. The proliferative response induced in D10.G4 cells by IL-1 + ionomycin but not that induced by IL-1 + PMA was sensitive to inhibition by FK-506 and CsA. In contrast, RAP inhibited equally well both types of stimulation. Finally, T cell proliferation driven by IL-2 or IL-4 was found to be relatively resistant to FK-506 or CsA but sensitive to RAP. Altogether, these data demonstrate that FK-506 and CsA alter similar calcium-associated events of T cell activation and block T cell proliferation primarily by suppressing lymphokine production. RAP interferes with a different set of events and inhibits T cells by impairing their response to growth-promoting lymphokines.