Amino acid position 11 of HLA-DRß1 is a major determinant of chromosome 6p association with ulcerative colitis.

The major histocompatibility complex (MHC) on chromosome 6p is an established risk locus for ulcerative colitis (UC) and Crohn's disease (CD). We aimed to better define MHC association signals in UC and CD by combining data from dense single-nucleotide polymorphism (SNP) genotyping and from imputation of classical human leukocyte antigen (HLA) types, their constituent SNPs and corresponding amino acids in 562 UC, 611 CD and 1428 control subjects. Univariate and multivariate association analyses were performed, controlling for ancestry. In univariate analyses, absence of the rs9269955 C allele was strongly associated with risk for UC (P = 2.67 × 10(-13)). rs9269955 is a SNP in the codon for amino acid position 11 of HLA-DRß1, located in the P6 pocket of the HLA-DR antigen binding cleft. This amino acid position was also the most significantly UC-associated amino acid in omnibus tests (P = 2.68 × 10(-13)). Multivariate modeling identified rs9269955-C and 13 other variants in best predicting UC vs control status. In contrast, there was only suggestive association evidence between the MHC and CD. Taken together, these data demonstrate that variation at HLA-DRß1, amino acid 11 in the P6 pocket of the HLA-DR complex antigen binding cleft is a major determinant of chromosome 6p association with UC.

Interleukin-18 system plays an important role in keloid pathogenesis via epithelial-mesenchymal interactions.

BACKGROUND: Keloid scarring is a dermal fibroproliferative disorder characterized by increased fibroblast proliferation and excessive production of collagen and extracellular matrix (ECM) components. To date, the role of cytokines in keloid pathogenesis has not been completely unravelled. Interleukin (IL)-18 is a pro-inflammatory cytokine that plays important roles in wound healing, fibrogenesis and carcinogenesis. OBJECTIVES: Our aim was to study the role of the IL-18 system in keloid pathogenesis. MATERIALS AND METHODS: Expression and localization of IL-18 and its receptor (IL-18R) were investigated in normal skin and keloid tissues using Western blot and immunohistochemistry. We further studied the expression of the IL-18 system in normal and keloid-derived cell lines in a coculture model. RESULTS: Results from Western blot and immunohistochemistry revealed that IL-18, IL-18Rα and IL-18Rß expression was elevated in keloid tissue compared with normal skin tissue. Studies on the expression of IL-18 and its antagonist, IL-18 binding protein (IL-18BP), using a coculture model demonstrated severe IL-18/IL-18BP imbalance in keloid keratinocyte/keloid fibroblast (KK/KF) cocultures with significant elevation of bioactive IL-18 whereas IL-18BP levels remained the same. This overproduction of bioactive IL-18 in keloid cocultures could be due to increased caspase-1 and decreased caspase-3 expression in keloid tissue, as well as decreased soluble IL-10 levels observed in keloid cocultures. The important inductive effects of IL-18 on KFs were further underscored by the observation that exposure of KF to IL-18 resulted in increased collagen and ECM component synthesis, and increased secretion of profibrotic cytokines such as IL-6 and IL-8. Finally, the addition of phosphatidylinositol 3-kinase (PI3K), mitogen activation protein kinase (MAPK), specificity protein 1 (Sp1) and mammalian target of rapamycin (mTOR) inhibitors inhibited IL-18 secretion in keloid cocultures. CONCLUSIONS: The present study has proven that the IL-18 system plays an important role in keloid pathogenesis via epithelial-mesenchymal interactions. It also suggests a therapeutic potential of PI3K, MAPK, Sp1 and mTOR inhibitors in the treatment of keloid scarring.

The expression of TSLP receptor in chronic rhinosinusitis with and without nasal polyps.

Chronic Rhinosinusitis with or without Nasal Polyps (CRSwNP and CRSsNP) may be characterized by different cytokine profiles. Generally, Th2 cytokines and eosinophilic infiltration have been reported to be more specific of CRSwNP compared to CRSsNP, where neutrophils seem to play a major role. The epithelial cell-derived thymic stromal lymphopoietin (TSLP) has been recently identified as a key factor in Th2-inflammatory response. The aim of this study is to investigate the expression of TSLP Receptor (TSLP R) in surgical specimens obtained from patients affected by CRSwNP (n=10) and CRSsNP (n=5) by immunohistochemical techniques (immunostaining score, IS). TSLP R expression was significantly higher in the inflammatory infiltrate and in the epithelial cells of CRSwNP, CRSsNP patients compared to the control group (IS 4.5±0.68, 4.4±1.44 and 0.43±0.3 respectively, p=0.0024 for inflammatory infiltrate and IS 5.8±0.92, 7.8±2.06 and 0.86±0.55 respectively, p=0.0018 for epithelial cells). No significant difference was observed in IS of inflammatory infiltrate and epithelial cells in CRSwNP compared to CRSsNP. Very low IS for TSLP R was found in connective tissue of all the samples, with no difference among the groups. TSLP receptor is highly expressed in CRS compared to controls and independently from the polyps suggesting an early common inflammatory pathway in the two CRS phenotypes.

Exhaled nitric oxide and nitric oxide synthase expression in Hodgkin's disease.

Hodgkin's disease (HD) is a malignant lymphoma with frequent mediastinal involvement, characterized by a significant inflammatory infiltration. Exhaled nitric oxide (FENO), is present in healthy humans, and has been proven to be increased in eosinophilic diseases such as allergic asthma. We investigated whether FENO is increased in mediastinal HD and whether NO is produced by lymphoma tissue. To this aim FENO was measured in 56 HD patients, 17 with and 39 without bulky mediastinal involvement, in the period from January 2007 to December 2008. Thirty-seven patients were reassessed after remission. Lymph node biopsies of 10 patients were evaluated for inducible (iNOS) and constitutive (eNOS) nitric oxide synthase expression by immunohistochemistry. FENO resulted significantly related to the mediastinal mass maximum diameter (p=0.009) and was significantly higher in patients with as compared to those without bulky mediastinal disease (38.7 ppb, CI 95% 19.3-58.0, versus 20.7 ppb, CI 95% 16.6-24.7; p=0.009). iNOS and eNOS immunoreactivity was observed in tumour and inflammatory cells (eosinophils and histiocytes). Only in patients with bulky mediastinal HD there was a significant decrease in FENO (from 50.4 ppb CI 95% 18.0-82.8 to 11.1 ppb CI 95% 4.4-17.8, p=0.011). In conclusion, high FENO and NOS expression in lymph-nodes indicate that NO is a component of the inflammatory network of HD. FENO may be proposed for the assessment and follow up of bulky mediastinal HD patients.

Osteo-promoting activity of OSTEOPLANT ANGIOSTAD in vitro.

AIM: There is an increasing need for an appropriate and readily-available material to reconstruct large bone defects, one of the most significant problems in the dental and maxillo-facial fields. The in vitro study examines the effects of OSTEOPLANT ANGIOSTAD, a product developed to increase osteoinductivity. METHODS: The product's biological properties were assessed by examining: the viability of cultured bone-marrow mesenchymal stem cells (MSC) through the methylthiazol tetrazolium assay; transforming growth factor (TGF)-b release by these cells through the enzyme-linked immunosorbent assay (ELISA) and the migration capacity of MSC and endothelial cells, by the in vitro wound closure test and transwell-migration assay, respectively. RESULTS: OSTEOPLANT ANGIOSTAD preserved MSC's viability and improved their capacity to release TGF-b1. It also increased in vitro wound healing by MSC and migration of endothelial cells. CONCLUSION: The results show that, since it increases the production by MSC of proangiogenic factors such as TGF-beta and promotes endothelial cell migration, OSTEOPLANT ANGIOSTAD may be an appropriate adjunct to accelerate the osteointegration of bone substitutes.

Increased intrathecal TGF-beta1, but not IL-12, IFN-gamma and IL-10 levels in Alzheimer's disease patients.

An inflammatory response has been hypothesised to be involved in the pathogenesis of primary dementias, above all Alzheimer's disease (AD). This study was aimed at evaluating interleukin (IL)-12 and a panel of related cytokine levels in paired CSF and sera of demented patients. IL-12 (p70 heterodimer and total IL-12 p40 chain), interferon (IFN)-gamma, IL-10 and transforming growth factor (TGF)-beta1 levels were measured in 30 patients with probable Alzheimer's disease (PrAD), 57 patients with other dementing disorders, including probable vascular dementia (PrVD), Parkinson's disease (PD) and normal pressure hydrocephalus (NPH), and 25 cognitively normal control subjects. In the presence of unchanged concentrations of IL-12, IFN-gamma and IL-10, the mean CSF level of TGF-beta1 and the correspondent TGF-beta1 index, but not the serum level, were significantly increased in PrAD compared to controls and PrVD, whereas no difference was found vs. NPH and PD. Our results support the pathophysiological role of TGF-beta1 system in AD.

[Biological aspects of pancreatic cancer]. / Aspetti bbiologici del carcinoma pancreatico.

Pancreatic ductal carcinoma still is an aggressive disease with a fatal prognosis due to late diagnosis and resistance to pharmacological and surgical treatments. Molecular investigations of pancreatic cancer are complicated by the restricted accessibility of the organ for biopsies. However, recent studies have indicated that pancreatic cancer is a multi-stage process resulting from the accumulation of genetic changes in the somatic DNA of normal cells. These molecular alterations, including overexpression of receptor-ligand systems, oncogene activation and loss of tumour suppressor genes, leads to a profound disturbance in cell cycle regulation and continuous growth. The molecular findings are now integrated in a pancreatic tumour progression model, with genetically and morphological defined precursor lesions. However, it remains unclear whether the initial target cells of this cancer develop from ductal or acinar cells. This review will present recent emerging questions on the biology of pancreatic cancer with particular emphasis on the cell origin and tumour microenvironment.

Interstitial cells of Cajal, enteric nerves, and glial cells in colonic diverticular disease.

BACKGROUND: Colonic diverticular disease (diverticulosis) is a common disorder in Western countries. Although its pathogenesis is probably multifactorial, motor abnormalities of the large bowel are thought to play an important role. However, little is known about the basic mechanism that may underlie abnormal colon motility in diverticulosis. AIMS: To investigate the interstitial cells of Cajal (the gut pacemaker cells), together with myenteric and submucosal ganglion and glial cells, in patients with diverticulosis. PATIENTS: Full thickness colonic samples were obtained from 39 patients undergoing surgery for diverticulosis. Specimens from tumour free areas of the colon in 10 age matched subjects undergoing surgery for colorectal cancer served as controls. METHODS: Interstitial cells of Cajal were assessed using anti-Kit antibodies; submucosal and myenteric plexus neurones and glial cells were assessed by means of anti-PGP 9.5 and anti-S-100 monoclonal antibodies, respectively. RESULTS: Patients with diverticulosis had normal numbers of myenteric and submucosal plexus neurones compared with controls (p = 0.103 and p = 0.516, respectively). All subtypes of interstitial cells of Cajal were significantly (p = 0.0003) reduced compared with controls, as were glial cells (p = 0.0041). CONCLUSIONS: Interstitial cells of Cajal and glial cells are decreased in colonic diverticular disease, whereas enteric neurones appear to be normally represented. This finding might explain some of the large bowel motor abnormalities reported to occur in this condition.

Phase II study of cisplatin, gemcitabine and 5-fluorouracil in advanced pancreatic cancer.

BACKGROUND: The aim of this study was to determine the activity of the combination of cisplatin, gemcitabine and 5-fluorouracil (5-FU) as therapy for metastatic or locally advanced inoperable pancreatic adenocarcinoma. PATIENTS AND METHODS: Patients with histologically proven advanced or metastatic pancreatic adenocarcinoma received first-line chemotherapy comprising cisplatin (20 mg/m2 on days 1, 8, 15, 22, 29 and 36), gemcitabine (1000 mg/m2 on days 1, 8, 29 and 36) and 5-FU (200 mg/m2 as continuous infusion on days 1-42) every 56 days. RESULTS: A total of 34 patients were studied. Eighty courses were administered (median two courses per patient). Among 32 patients evaluable for response, two patients had a complete response and four a partial response for an overall response rate of 19% (95% confidence interval 7% to 36%). Thirteen patients had stable disease (40%) and 13 progressed. Median progression-free survival was 4.7 months, median survival 9.0 months and 26% of patients achieved 1-year survival. Ten of 25 patients (40%) with pain at presentation had a sustained reduction of analgesic consumption. The principal grade 3/4 toxicities were neutropenia, thrombocytopenia, anaemia and mucositis, occurring in 24%, 21%, 9% and 3% of patients. CONCLUSION: This schedule seems well tolerated and active in pancreatic cancer and worthwhile of further evaluation.

Transforming growth factor-beta and interleukin 10 in oral implant sites in humans.

Cross-talk between cells and cytokines in peri-implant tissue is largely unknown. The immune response in the gingival mucosa appears to favor implant integration over rejection, since titanium-implant-retained overdentures show long-term success. This study evaluates pro-inflammatory (interleukin [IL]-2, interferon [IFN]-gamma, IL-12) and anti-inflammatory (IL-4, IL-10, transforming growth factor [TGF]-beta1) cytokine mRNA expression and tissue morphometry in peri-implant soft tissue from patients before and during treatment with Brånemark titanium implants. Immediately after treatment with endosseous implant and overdenture, TGF-beta1 mRNA increased in peri-implant mucosa specimens; transcript accumulation for IL-10 was elevated at 4 months and decreased dramatically thereafter. Transcripts for IL-2, IFN-gamma, IL-12, and IL-4 were absent. Healthy osseointegrated implants showed no histological inflammation in most patients. These findings suggest that newly classified TGF-beta and/or IL-10 secreting T regulatory (r)/T helper (h)-3 cells may populate implant insertion sites.

Expression of transforming growth factor-beta isoforms in the skin, kidney, pancreas and bladder in a German shepherd dog affected by renal cystadenocarcinoma and nodular dermatofibrosis.

The present study was performed to assess the expression of isoforms 1, 2 and 3 of transforming growth factor (TGF)-beta in skin nodular dermatofibrosis lesions, kidney, bladder and pancreas from a 10-year-old female German shepherd dog (GSD) affected by renal cystadenocarcinoma and nodular dermatofibrosis (RCND) compared with normal GSDs (n = 2). Formalin-fixed, paraffin-embedded tissues obtained from the dog affected by RCND, diagnosed by renal ultrasonography and histopathological examination were analysed by immunohistochemistry using polyclonal antibodies to TGF-beta1, 2 and 3, and evaluated semiquantitatively using an immunoreactivity score. Similar expression of TGF-beta2 and TGF-beta3 was observed in all tissue specimens in both the RCND-affected animal and normal dogs. In contrast, TGF-beta1 immunoreactivity was increased in the derma of the RCND canine. Comparable TGF-beta1 serum levels were found between the diseased and normal animals. The increased local cutaneous production of TGF-beta1 in the RCND dog, compared with the normal animals, suggests that this cytokine may play an important role in the induction of nodular dermatofibrosis associated with renal cystadenocarcinoma.

[The pro-apoptotic factors Fas Ligand and Trail. Molecular mechanisms, physiopathological role and therapeutic potential]. / I fattori pro-apoptotici Fas Ligando e Trail. Meccanismi molecolari, ruolo fisiopatologico e potenzialità terapeutiche.

Programmed cell death, also known as apoptosis, is a normal physiologic process which occurs during embryonic development as well as in maintenance of tissue homeostasis. Increasing evidence suggests that alterations in cell death contribute to the pathogenesis of a number of human diseases, including cancer, viral infections, autoimmune diseases and acquired immunodeficiency syndrome (AIDS). The extraordinary research activity of the past few years has resulted in the characterization of the principal proteins involved in the apoptosis machinery. An area of particular interest has been the induction of apoptosis by two death receptor/ligand pairs, Fas/Fas Ligand and DR4-DR5/TRAIL. The identification of these molecules with the recruited signaling pathways could clarify their physiopathological implications, having a significant impact upon potential therapeutic interventions in diseases associated with cell survival alterations.

Aberrant activation of c-kit protects colon carcinoma cells against apoptosis and enhances their invasive potential.

Multiple genetic aberrations contribute to the development of biologically aggressive, clinically malignant colorectal carcinomas (CRCs). Some of these have been linked to inappropriate signaling through the tyrosine kinase moieties of growth factor receptors. We have described previously (G. Bellone et al., J. Cell. Physiol., 172: 1-11, 1997) that human CRCs overexpress both the receptor tyrosine kinase c-kit and its ligand, stem cell factor (SCF), relative to normal mucosa cells, thus establishing an autocrine c-kit-mediated loop. In addition, we noted that exogenous SCF contributes to anchorage-independent growth of HT-29 colon carcinoma cells in semisolid medium. Here, we investigated possible roles of the c-kit/SCF autocrine/paracrine system in survival and invasive capacity of DLD-1 colon carcinoma cells. We report that SCF was required for migration and invasion of DLD-1 cells through reconstituted basement membranes (Matrigel) and up-regulated gelatinase (matrix metalloproteinase-9) activity in DLD-1 cells. Furthermore, we describe that SCF supported survival of DLD-1 cells in growth factor-deprived conditions. These results suggest multiple roles of c-kit activation in support of the malignant phenotype of DLD-1 cells related to growth, survival, migration, and invasive potential.

Differential expression of transforming growth factors-beta1, -beta2 and -beta3 in human colon carcinoma.

Transforming growth factor (TGF)-beta is a protein family which affects multiple cellular functions including survival, proliferation, differentiation and adhesion. Among the three known isoforms, TGF-beta1 is commonly overexpressed in solid malignancies. Recent studies in knock-out mice demonstrated non-redundant roles of different TGF-beta isoforms in development. The present study was performed to assess tumour-associated expression of the three TGF-beta isoforms in colon carcinoma. We report that colon carcinoma progression is associated with gradual and significant increases in expression of TGF-beta1 and TGF-beta2 mRNA and proteins. By contrast, TGF-beta3 expression was detected in normal colonic mucosa and, at slightly higher levels, in tumour tissues. In addition, plasma levels of both TGF-beta1 and TGF-beta2 were significantly higher in cancer patients when compared with unaffected individuals. Taken together, our results indicate distinct expression patterns of the three TGF-beta isoforms in colon carcinoma cells and possible systemic effects of TGF-beta1 and TGF-beta2 in tumour patients.

In vitro effect of transforming growth factor-beta on adhesion molecule expression by human gingival fibroblasts cultured in the presence of a titanium abutment.

BACKGROUND: There is little information in the literature on the structural basis mediating gingival cell adhesion to the surface of titanium abutments. We cultured gingival fibroblasts on a titanium abutment creating as closely as possible the in vivo state. We analyzed the constitutive and transforming growth factor (TGF) beta-induced expression of the adhesion molecules CD44, CD49b, CD49c, CD51, CD54, and CD61 and extracellular matrix (ECM) components fibronectin, laminin and collagen IV. METHODS: Three totally edentulous patients underwent implant treatment to anchor the mandibular denture on 2 implants. Gingival mucosa cell specimens were collected from the mandible during the first surgical stage and the gingival fibroblast cultures were prepared. Cells were cultured for 48 hours with or without isoforms TGF-beta1, TGF-beta2, and TGF-beta3. The expression of adhesion molecules and ECM components was analyzed by immunofluorescence staining and flow cytometry. RESULTS: The addition of TGF-beta isoforms to the cell culture over the incubation period had little effect on cell growth rate, but significantly influenced cell orientation, which changed from a sun-burst pattern in control conditions to a more elongated organization and perpendicular to abutment surface. In all fibroblast preparations, a marked expression of CD44 and a moderate positivity for anti-CD49b and CD49c were found. By contrast, CD51, CD54, and CD61 expressions were negligible. When fibroblasts were cultured for 48 hours in the presence of TGF-beta, the expression of most of the receptor molecules increased. The cells expressed constitutively moderate levels of laminin and fibronectin and low amounts of collagen IV. By contrast, treatment with any one of the 3 TGF-beta isoforms greatly enhanced the expression levels of fibronectin, laminin, and, especially, collagen IV. CONCLUSIONS: TGF-beta not only seems to affect the orientation of the cultured gingival fibroblasts, but also to induce a clear-cut modification of their adhesion molecule expression.

Cytokine production and bone remodeling in patients wearing overdentures on oral implants.

The stability of titanium dental implants is determined by osseointegration. Bone is a dynamic tissue continuously remodeled through resorption and formation, processes controlled by local cytokine production. This study investigated osseotropic cytokine expression in gingival mucosa, in the intraforamina and inferior first molar zones, during rehabilitation with implant-retained overdentures. Specimens were taken from six patients prior to placement of implants in the intraforamina bone; at connection of healing abutments; and 4, 8, and 12 months after prosthetic anchorage. Through semi-quantitative reverse-transcriptase polymerase chain-reaction, the following constitutively expressed cytokines were found at first surgical stage: interleukin-1, -6, and -8; small amounts of interleukin-11; stem cell factor; and transforming growth factor-beta1, -beta2, and -beta3. From the connection of healing abutments to 12 months after prosthetic anchorage, transforming growth factor-beta1, -beta2, and -beta3 were markedly higher than initial values. Expression of interleukin-6 and -8 decreased 8 months after prosthetic anchorage, while that of interleukin-1 increased at 12 months. In cultured gingival fibroblasts, modulation of cytokine secretion was also time-dependent. Cell culture supernatants influenced osteoclast-like multinucleated cell formation in long-term human marrow culture or osteoblast function, depending on the cytokine profile produced. These results are consistent with functional contributions of cytokines to osseointegration and minimization of posterior edentulous zone bone resorption.

Production and pro-apoptotic activity of soluble CD95 ligand in pancreatic carcinoma.

We report here that the progression of pancreatic carcinomas in tumor patients is associated with increased serum levels of both the soluble forms of CD95 ligand (CD95L/FasL) and its receptor, CD95 (Fas). Shedding of proteolytically processed soluble CD95L was also observed in pancreatic carcinoma cells in vitro, thus identifying one possible source of CD95L in patients' sera. Because the secreted forms of both CD95 and CD95L have been implicated previously in protection of cells from CD95-mediated cell death, we assessed the effect of soluble CD95L in supernatants of pancreatic carcinoma cells on viability of Jurkat T lymphocytes. We describe that (a) supernatants derived from cultured pancreatic carcinoma cells caused apoptosis of Jurkat cells; (b) soluble tumor-derived CD95L contributed significantly to this effect; and (c) in comparison to Jurkat cells, pancreatic carcinoma cells themselves revealed increased resistance to apoptosis induction by autocrine soluble CD95L. These results are consistent with the notion that in the microenvironment of pancreatic tumors, tumor-derived shed CD95L exerts paracrine pro-apoptotic effects. In addition, because it is released at high levels into the bloodstream, soluble CD95L may have systemic effects in tumor patients that reach beyond the microenvironment of the tumor site.

Association between elevated prolactin levels and circulating erythroid precursors in dialyzed patients.

The prolactin (PRL) receptor (R), a member of the cytokine hemopoietin receptor superfamily, has been shown to activate early differentiation steps along the erythroid pathway. In particular PRL, a product of bone marrow stroma, induces functional erythropoietin (EPO)-R on CD34+ hemopoietic progenitors. In this study, expression of EPO-R mRNA and responsiveness to EPO were assessed on enriched hemopoietic progenitor cells (HPC) from seven hyperprolactinemic and three normoprolactinemic patients and two normal subjects. Expression of EPO-R mRNA by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) was found in HPC of four out of seven hyperprolactinemic patients but not in normoprolactinemic patients or normal donors. Development of EPO-dependent Colony Forming Unit-Erythroid (CFU-E) colonies in semi-solid medium was observed only in hyperprolactinemic patients (six out of seven). A much higher number of CFU-E colonies was observed in the four patients with a positive EPO-R message. We conclude from these data that abnormally high levels of PRL may increase the number of EPO-responsive hemopoietic precursors in vivo as they do in vitro. Since hyperprolactinemia associates in these patients with depressed EPO production, it may be regarded as a compensatory mechanism for the reduced availability of the hemopoietic factor.

Up-modulation of interferon-gamma mediates the enhancement of spontanous cytotoxicity in prolactin-activated natural killer cells.

Prolactin (PRL) has been shown to participate in lymphocyte activation. In particular, the constitutive natural killer (NK) and the lymphokine-activated killer (LAK) cytotoxicity of CD56+ CD16+ cells is increased by its physiological to supraphysiological concentrations. As PRL has been shown to up-regulate the production of interferon-gamma (IFN-gamma) by peripheral blood mononuclear cells, we studied its effect on IFN-gamma production by NK cells as a possible mechanism of autocrine activation of cytotoxicity. Released and intracellular IFN-gamma, as well as IFN-gamma mRNA expression, were increased by pituitary and recombinant human PRL, which stimulated optimal NK and LAK cytotoxicity. Treatment with blocking anti-IFN-gamma monoclonal antibody (mAb) selectively affected PRL-increased killing of K562 targets, demonstrating that PRL-mediated enhancement of spontaneous cytotoxicity depends, at least in part, on up-regulation of IFN-gamma.