C. Scheibenbogen

Elevation of serum interleukin-6 concentration precedes acute-phase response and reflects severity in acute pancreatitis

Experimental studies have shown that interleukin-6 induces all major acute-phase proteins in the liver, including C-reactive protein. In 50 patients with acute pancreatitis, the serum concentrations of interleukin-6 and C-reactive protein were determined daily during the first week of hospitalization. Patients were divided into three groups according to clinical criteria: mild pancreatitis (less than or equal to 1 complication; n = 25), severe pancreatitis (greater than or equal to 2 complications; n = 15), and lethal outcome (n = 10). Patients with mild disease showed initially slightly elevated levels of interleukin-6 (22.0 +/- 9.8 U/mL) that decreased to low levels within 4 days (5.0 +/- 1.0 U/mL). In patients with severe pancreatitis, serum concentrations of interleukin-6 were initially clearly elevated (35.0 +/- 7.5 U/mL) and remained slightly elevated until day 7 (13.0 +/- 2.0 U/mL). Patients with lethal outcome had markedly elevated initial interleukin-6 concentrations (61.0 +/- 15.0 U/mL) that decreased but were still elevated at day 7 (26.0 +/- 2.5 U/mL). In all three groups, C-reactive protein concentrations followed the course of interleukin-6 concentrations by 1 day. There was a positive correlation between maximal interleukin 6 concentrations and maximal increases in the serum concentrations of C-reactive protein (r = 0.66). At days 1 and 2, increased (greater than 15 U/mL) interleukin-6 concentrations (positive predictive value, 91%; negative predictive value, 82%) predicted a severe or lethal course of the disease more accurately than elevated [greater than 0.10 g/L (greater than 10 mg/dL)] C-reactive protein concentrations (positive predictive value, 67%; negative predictive value, 79%). In conclusion, elevated serum concentrations of interleukin-6 followed by increased levels of C-reactive protein reflect the severity of acute pancreatitis.

Surface Phenotype Analysis of Human Monocyte to Macrophage Maturation

Cells of the mononuclear phagocyte system arise from circulating blood monocytes. Upon emigration from the vasculature, monocytes differentiate into macrophages, a process that monocytes similarly undergo in vitro. We have established primary cultures from elutriated or adherence‐purified blood monocytes and analyzed the antigenic modulation during monocyte to macrophage transformation, which could be followed by the expression of specific antigens and which required as yet unknown inducer signals present in the serum. It is shown that in the absence of serum monocytes only survive in vitro when cultured adherent to plastic but rapidly die in suspension culture. Starting at 0.5%, serum induced maturation dose‐dependently, with the optimal concentration being 2 to 5%. Of those antigens not present on monocyte, the low‐affinity Fc receptor (CD16), the α‐chain of the vitronectin receptor (CD51), gp65‐MAX.1, and gp68‐MAX.3 were expressed only upon serum‐induced macrophage differentiation, whereas the transferrin receptor (CD71), MAX.26, and to some degree also gp65‐MAX.11 appeared to be independent of maturation and were also found on primary cultures of adherent monocytes under serum‐free conditions. In addition, the rapid induction of HLA class II antigens (within 24 hr) was similar with and without serum, as was the continued high‐density expression in long‐term culture. The monocyte‐specific CD14 antigen was down‐regulated in the absence of serum but kept its level of expression on differentiated macrophages. In comparison, alveolar and peritoneal macrophages, respectively, differed in their antigenic phenotype: Alveolar macrophages expressed high HLA class II antigens but low CD14, whereas for peritoneal macrophages the opposite was found. Both interferon‐γ and ‐α suppressed macrophage maturation in vitro but had contrary effects on HLA class II and CD16 expression: Interferon‐γ up‐regulated the two types of antigens, which, in contrast, were down‐regulated by interferon‐α.

Interferon-gamma-induced expression of tissue factor activity during human monocyte to macrophage maturation

The expression of tissue factor (TF) during differentiation of human monocytes (MO) to macrophages (MAC) in vitro is investigated in this study. In MO, TF activity can be induced by the addition of lipopolysaccharides (LPS) as detected by Northern blot analysis and measured functionally as procoagulant activity (PCA), while IFN gamma alone has only marginal stimulatory activity. During in vitro differentiation of MO into MAC, however, there is a steady increase in IFN gamma-induced PCA with a maximum on day 7. While MO during the first 2 days in culture are more responsive to LPS, IFN gamma becomes the prominent stimulus for mature MAC. The response to IFN gamma is rapid with a peak within 6-8 h and a subsequent downregulation to baseline activity within 24 h. Our results demonstrate that IFN gamma can effectively induce TF in human MAC and that its expression is developmentally regulated during MO to MAC maturation in vitro.

Intrahepatic adoptive immunotherapy with autologous tumorcytotoxic macrophages in patients with cancer

Adoptive transfer of cytotoxic macrophages (MAC) may be able to correct for a defective generation of competent effector cells in patients with cancer. Here we report on a Phase I trial of adoptive transfer of autologous MAC by hepatic artery infusion in seven patients with metastatic liver disease. Clinical side effects were mild and consisted of fever and flu-like symptoms. Serum levels of C-reactive protein (CRP) increased within hours after MAC transfer and rose further in the course of repeated therapies. An increase of thrombin-anti-thrombin III complexes occurred in 31% of therapies. Serum neopterin, interleukin (IL)-6, and IL-8 did not change during therapy. In vivo tracing of 111 indium-labeled MAC revealed that on average, 43% of whole-body activity remained in the liver for 7 days. Evidence for tumor response could not be demonstrated. In conclusion, isolated liver perfusion with autologous MAC is well tolerated and induces a profound biological response in the recipient. Regional adoptive immunotherapy might be able to built up, in proximity to metastatic lesions, a potent cytotoxic cell infiltrate that could then be triggered within the patient using exogenous stimuli like endotoxin, cytokines, or other MAC activators.

The interleukin-2 receptor in human monocytes and macrophages: regulation of expression and release of the α and β chains (p55 and p75)

Human monocytes constitutively express the intermediate-affinity interleukin-2 receptor (IL2R) p75, while freshly isolated monocytes lack the low-affinity IL2R p55 (Tac antigen, CD25). Lipopolysaccharide (LPS) upregulates expression of p75 and effectively induces surface expression of CD25 on human monocytes within 18 h, as detected by two-colour FACS analysis on 59.5 +/- 7.6% of cells. IL2-binding studies using biotinylated IL2 reveal the presence of a functional high-affinity receptor on LPS-activated monocytes. Soluble CD25 (sCD25) is not released into supernatants of elutriation-purified monocytes cultured for 24 h with 100 ng/ml LPS. When these monocytes are cultured for up to 7 days in the presence of serum to induce differentiation into macrophages, increasing amounts of sCD25 can be measured in the 24-h supernatants induced with LPS (173 +/- 86 U/ml at day 7), whereas the percentage of CD25+ cells (14.8 +/- 14.1% at day 7) is significantly lower than in monocytes. Thus, the cell surface expression and release of CD25 is differentially regulated in activated monocytes and macrophages.

Regulation of Neopterin Secretion during Human Monocyte to Macrophage Differentiation in Vitro

Human mononuclear phagocytes (MP) can release neopterin upon induction of indoleamine 2,3-dioxygenase and subsequent degradation of L-tryptophan (1). While this pathway can be induced in a variety of other normal and neoplastic cells, MP are the only cell type able to release neopterin in significant amounts (2). They do so in response to various stimuli of which interferon-gamma (IFNg) is the most potent one. Thus, neopterin secretion is regarded to sensitively indicate a successful activation of MP through T -lymphocyte mediated immune response (3) and neopterin has indeed found increasing attention as a marker of clinical disease activity in cell-mediated immunity (4). As the functional competence of MP is regulated both by activating and differentiation-inducing signals we were interested in studying the ability of MP at defined stages of differentiation to respond to activation by releasing neopterin. Peripheral blood monocytes (MO) represent only short-lived precursor cells able to differentiate into inflammatory or resident macrophages (MAC) upon migration from the vasculature to the various tissues (5). This MO to MAC differentiation can be studied in vitro where blood MO transform into exudate-type MAC under appropriate conditions in the presence of serum (6). It is shown that for both the IFNgand LPS-induced secretion of neopterin maturation of MO is required.

Secretion of Colony-Stimulating Factor for Macrophages (M-CSF) and Granulocyte/Macrophages (GM-CSF) is Developmentally Regulated in Human Macrophages*

Cells of the mononuclear phagocyte system (MPS) are involved in the immune surveillance against microbial pathogens and malignant cells but are also important regulator cells in hematopoiesis [1, 2]. They are able to secrete a variety of factors that suppress or sitmulate the proliferation and differentiation of hematopoietic progenitor cells. Of these, macrophage colony-stimulating factor (M-CSF) and granulocyte-CSF have been shown to be released from monocytes [3], whereas the synthesis of GM-CSF is disputed [3, 4]. However, monocytes have to undergo maturation into macrophages to acquire the functional competence which is significant in vivo [5–7].

Adoptive Transfer of Autologous Cytotoxic Macrophages Grown from Blood Monocytes. A New Approach to Cancer Immunotherapy

Clinical trials to evaluate the potential of adoptive immunotherapy in cancer patients have been restricted to the use of lymphoid effector cells [1,2]. Of the other probably even more important host defense system against tumor growth, the mononuclear phagocyte system [3], only monocytes (mo) have been reinfused [4] which, however, represent immature precursor cells and acquire full functional competence only upon further maturation. This might at least in part be due to the many technical problems associated with the generation of human mature macrophages (MO).