Therapy with interferon alfa and ribavirin in patients with chronic hepatitis C and normal levels of alanine aminotransferase

The aim of the study was to evaluate the efficacy of combination therapy with interferon-alpha (IFN-alpha) and ribavirin in patients with chronic hepatitis C and normal alanine aminotransferase (ALT) values. In this retrospective study, 12 HCV-RNA positive patients (7 males and 5 females, mean age 38.1 years), treated between 1998 and 2001, with normal or near normal ALT values on three consecutive occasions and histologically mild disease were identified. During the induction period of four weeks they received 56 MU IFN-alpha 2b and ribavirin 1000 mg daily. During the next 44 weeks they received 3 MU IFN-alpha 2b three times a week with ribavirin 1000 mg daily. Seven out of 12 (58%) patients were HCV-RNA negative at the end of the therapy (end-of-treatment-response) and 5 of 12 (42%) showed sustained virologic response at 6 months. No significant elevation of aminotransferase values was recorded during therapy. Patients with mild chronic hepatitis C and normal ALT levels respond well to combination therapy with interferon and ribavirin, similar to those with elevated ALT levels. As long as the natural history and long-term outcome of these patients are not completely known, this might be a beneficial treatment option.     

比较α-干扰素不同联合治疗方案对儿童HBeAg阳性慢性乙型肝炎的疗效

目的评估两种不同的α-干扰素联合治疗对儿童HBeAg阳性慢性乙型肝炎的临床疗效。方法选择HBeAg阳性慢性乙型肝炎儿童120例,随机分为3组,每组各40例:第1组(A组)为α-干扰素(IFN-α)组;第2组(B组)为IFN-α 拉米夫定(LAM)组。第3组(C组)为α-干扰素(IFN-α) 乙肝疫苗组。其中干扰素疗程6个月,拉米夫定疗程6个月,所有病例均观察至12个月。结果治疗结束时丙氨酸转氨酶(ALT)复常率3组无差异。治疗6个月和12个月时B组HBeAg阴转率和HBV DNA的阴转率明显高于A组和B组,差异有统计学意义(P<0.05)。结论α-干扰素与拉米夫定联合治疗对HBeAg阳性慢性乙型肝炎儿童的病毒学应答(VR)疗效明显优于单用α-干扰素组和α-干扰素 乙肝疫苗组。     

Modulation of the IL-12/IFN-gamma axis by IFN-alpha therapy for hepatitis C

Although IFN-alpha forms the foundation of therapy for chronic hepatitis C, only a minority of patients has a sustained response to IFN-alpha alone. The antiviral activities of IFN-alpha formed the rationale for its use in viral hepatitis. However, IFN-alpha and the other Type I IFNs are also pleiotropic immune regulators. Type I IFNs can promote IFN-gamma production by activating STAT4 but can also inhibit production of IL-12, a potent activator of STAT4 and IFN-gamma production. The efficacy of IFN-alpha in the treatment of hepatitis C may therefore depend in part on the balance of IFN-gamma-inducing and IL-12-suppressing effects. We characterized the effects of pegylated IFN-alpha therapy for hepatitis C on the capacity of patients' PBMC to produce IL-12 and IFN-gamma ex vivo. Cells from patients with a sustained virological response to therapy had significantly greater levels of IFN-alpha-driven IFN-gamma production prior to treatment than those from nonresponding patients. No differences in pretreatment IL-12 productive capacity were seen between patient groups. However, therapy with IFN-alpha led to suppression of inducible IL-12 production throughout the course of therapy in both groups of patients.     

Efficacy and long-term follow up of combination therapy with interferon alpha and ribavirin for chronic hepatitis C in Korea

Combination therapy with interferon alpha (IFN-alpha) and ribavirin for 24 or 48 weeks according to HCV genotype has improved the overall sustained virological response (SVR) rates to approximately 40%. The aim of this study was to investigate the long-term efficacy of combination therapy with IFN-alpha and ribavirin for chronic hepatitis C in Koreans. One hundred thirty-eight patients with chronic hepatitis C who received this combination therapy between 1995 and 2003 were analyzed retrospectively. All patients were treated with IFN-alpha 3-6 million units three times weekly in combination with 900-1200 mg/day of ribavirin for 24 weeks. The overall SVR rate was 41.3%. Patients were followed up for a median of 41 months (range, 12-105 months) after completion of therapy. In all of the SVR patients (57 patients), SVR was conserved during the follow-up period. None of the patients progressed to decompensated liver disease or hepatocellular carcinoma (HCC). However, 5 of the 81 non-SVR patients (6.2%) progressed to decompensated liver disease or HCC. In conclusion, combination therapy with IFN-alpha and ribavirin shows good long-term efficacy in patients with chronic hepatitis C in Korea, one of the highest endemic areas of hepatitis B virus (HBV) infection.     

Recombinant interferon alfa therapy for chronic hepatitis C. A randomized, double-blind, placebo-controlled trial

Infection with the hepatitis C virus may result in chronic liver disease for which no effective therapy is now available. We studied the effects of recombinant human interferon alfa in a prospective, randomized, double-blind, placebo-controlled trial in patients with well-documented chronic hepatitis C. Forty-one patients were enrolled in the trial, 37 of whom were later found to have antibody to hepatitis C virus. Twenty-one patients received interferon alfa (2 million units) subcutaneously three times weekly for six months, and 20 received placebo. The mean serum aminotransferase levels and the histologic features of the liver improved significantly in the patients treated with interferon but not in the patients given placebo. Ten patients treated with interferon (48 percent) had a complete response, defined as a decline in mean serum aminotransferase levels to the normal range during therapy; three others had a decrease in mean aminotransferase levels of more than 50 percent. After treatment ended, however, serum aminotransferases usually returned to pretreatment levels; 6 to 12 months after the discontinuation of interferon therapy, only two patients (10 percent) still had normal values. We conclude that interferon alfa therapy is beneficial in reducing disease activity in chronic hepatitis C; however, the beneficial responses are often transient.     

Efficacy of long-term interferon therapy in chronic hepatitis B patients with HBV genotype C

Infection with Hepatitis B virus (HBV) genotype C predominates in Japan. We analyzed the efficacy of interferon (IFN) alpha or beta in the treatment of chronic hepatitis B patients with HBV genotype C and the clinical predictors for therapeutic response. Forty-three genotype C-infected, chronic hepatitis B e antigen (HBeAg)-positive patients (32 men and 11 women with a mean age of 35.6+/-10.1 years) who had been treated with IFN therapy were retrospectively studied. The patients were classified into two treatment groups. Short-term therapy group was administered a 5-6 MU dose three times weekly for 4 weeks, and the long-term therapy group for 24 weeks. At the end of the follow-up period, 4 (15%) of 27 short-term therapy group patients and 6 (38%) of 16 long-term therapy group patients had normalized serum ALT levels and seroconversion of HBeAg to anti-HBe (p=0.137). Multivariate analysis for parameters most important for the efficacy of IFN therapy was performed using Cox proportional hazard models in order to investigate the association between baseline characteristics of patients and the response to IFN treatment. As a result, the p-values of IFN treatment group and sex were <0.05, and both factors can be recognized as independent significant factors (relative risk, 2.93 and 2.53; p=0.027 and 0.040, respectively). Furthermore, the cumulative rates of seroconversion of HBeAg to anti-HBe analyzed by the Kaplan-Meier method was significantly higher in the female group (p=0.015) and in the long-term IFN therapy group (p=0.0046). In summary, long-term IFN therapy may be more effective than short-term IFN therapy for patients with chronic HBV genotype C infection.     

Interferon response heterogeneity: activation of a pro-inflammatory response by interferon alpha and beta. A possible basis for diverse responses to interferon beta in MS

Interferon gamma (IFN-gamma) stimulates the (pro-inflammatory) type II interferon receptor and is known to exacerbate multiple sclerosis (MS). In contrast, IFN-alpha and IFN-beta are ligands for the (anti-inflammatory) type I interferon receptor and are beneficial in some (but not all) patients with MS. Should IFN-beta elicit a type-II-like pro-inflammatory response, the beneficial effects might be attenuated. These studies were undertaken to test this possibility with the use of quinolinic acid (QUIN) formation as a measure of type II receptor activation. In normal human macrophage cultures, IFN-gamma was the most potent stimulus for QUIN formation. Generally, IFN-beta and IFN-alpha were less potent. However, an unexpected inter-patient variability was observed. In some subjects, IFN-alpha was more potent than IFN-beta. In other subjects, IFN-beta was more potent than IFN-alpha. The present data demonstrate an inter-subject variability for QUIN production following exposure to the interferons. MS patients who demonstrate a pro-inflammatory response to IFN-beta (e.g., increased QUIN) may be less likely to benefit from this therapy.     

Serum interleukin-6 and interferon-gamma levels in patients with hepatitis B-associated chronic liver disease

Hepatitis B virus (HBV) infection can elicit a variety of clinical sequelae ranging from acute self-limited hepatitis to hepatocellular carcinoma, which are not attributable to a direct cytopathic effect of the virus but rather to the individual host's immune response. Cytokines, low-molecular-weight proteins with a broad range of activity, have been shown to be involved in the regulation of hepatocyte functions, as well as in the pathogenesis leading to liver damage. In the present study, we investigated the correlation between serum interleukin 6 (IL-6) and interferon gamma (IFN-gamma) in altogether 75 patients chronically infected with HBV. They comprised 15 asymptomatic carriers, 15 chronic persistent hepatitis (CPH) and 15 chronic active hepatitis (CAH) patients, 15 cases of cirrhosis and 15 patients with hepatocellular carcinoma (HCC) previously diagnosed by serology and histology, respectively. IL-6 and IFN-gamma levels in their sera were determined using a commercially available kit. Our results showed various concentrations of serum IL-6 detectable in 6.7% of asymptomatic carriers, 13.3% of patients with CPH, 20% of patients with CAH, 33.3% in cirrhotic patients and 66.7% in HCC. In contrast, serum IFN-gamma was only found in 13.3% of asymptomatic carriers and CAH, but could not be detected in the other groups. Our data demonstrated a positive correlation between serum IL-6 and clinical severity of chronic HBV infection, whereas the IFN-gamma levels appeared not to be correlated. From this we conclude that among chronic hepatitis patients IFN-gamma is mostly not expressed at a level detectable by serology, whereas according to other authors it is involved in the immediate immune response triggered by acute hepatitis. IL-6 on the other hand, might rather be responsible for liver inflammation and regeneration in chronic liver disease.     

Effectiveness of lamivudine and interferon-alpha combination therapy versus interferon-alpha monotherapy for the treatment of HBeAg-negative chronic hepatitis B patients: a randomized clinical trial.

Results comparing the effectiveness of lamivudine used as monotherapy or in combination with interferon-alpha (IFN-alpha) in the treatment of chronic hepatitis B are not conclusive. This study compared the effects of IFN-alpha alone or in combination with lamivudine for the treatment of hepatitis B e antigen (HBeAg)-negative patients with chronic hepatitis B. Participation of patients in the IFN-alpha monotherapy and combination groups was randomized to a 1:1 ratio. Twenty seven HBeAg-negative patients with chronic hepatitis B received IFN-alpha (13 patients) at 9 million units 3 times weekly for 24 weeks or IFN-alpha at 9 million units 3 times weekly for 24 weeks plus lamivudine 100 mg/day (14 patients) daily for 1 year. Hepatitis B virus (HBV) DNA was measured quantitatively by real-time polymerase chain reaction at 0, 6, 12 and 18 months after the start of treatment. Sustained virologic response was defined as non-detectable serum HBV DNA 72 weeks after starting treatment. Sustained biochemical response was defined as normalization of alanine aminotransferase (ALT) values 72 weeks after starting treatment. The baseline characteristics of the 2 treatment groups were similar with respect to age, gender, ALT, HBV DNA levels and histologic diagnosis. Sustained biochemical responses were found at week 72 in 7 patients in each group (54% with IFN-alpha monotherapy and 50% with combination therapy) [p>0.05]. Sustained virologic responses were found at week 72 in 5 patients (38%) in the monotherapy and 7 patients (50%) in the combination therapy group (p>0.05). Combination therapy was not superior to IFN-alpha alone for the treatment of chronic hepatitis B. Combination treatment was associated with some disadvantages, such as additional cost. Lamivudine, on the other hand, may be more suitable for patients with cirrhosis, non-responders to IFN-alpha or in cases with contraindication for IFN-alpha.     

Production of interferon alpha and interferon gamma by peripheral blood leukocytes from patients with chronic hepatitis B virus infection

Peripheral blood leukocytes from patients with chronic hepatitis B virus (HBV) infection were studied for their capacity to produce interferon (IFN) alpha or IFN gamma. Yields of IFN alpha in leukocyte cultures stimulated with influenza A virus or human leukemic cells were significantly lower than those obtained from healthy controls. Production of IFN gamma in response to induction with protein A of Staphylococcus aureus was also significantly diminished. Defects of IFN production in leukocyte cultures showed no correlation with active viral replication or the degree of severity of HBV-associated liver disease. The demonstration of partial defects of endogenous IFN production provides a rationale for using IFN replacement therapy in patients with chronic HBV infection.     

Multicenter randomized study comparing initial daily induction with high dose lymphoblastoid interferon vs. standard interferon treatment for chronic hepatitis C

One hundred fifty-five chronic hepatitis C patients were assigned at random to receive natural lymphoblastoid interferon (IFN)alpha-n1, s.c., for 13 months in one of three treatment regimens: initial daily induction with 10 million units (MU) followed (group 1, n = 50) or not (group 2, n = 52) by 1 month of rest and then three times weekly 10 MU (2 months), 5 MU (2 months), and 3 MU (8 months); group 3 (n = 53) received tiw 5 MU (2 months) followed by 3 MU (11 months). By intention-to-treat analysis, ALT normalization at completion of treatment was greater in patients who received continuous IFNalpha-n1 therapy with initial daily induction (group 2: 24/52, 46%) compared with those given intermittent therapy with initial daily induction (group 1: 17/50, 34%) and those who received standard IFNalpha-n1 therapy (group 3, 18/53, 34%; P not significant). The sustained ALT response was 26%, 27% and 21% and the sustained virological response was 20%, 27%, and 19%, in groups 1, 2, and 3, respectively. A trend was observed towards a higher biochemical and virological end-of-treatment response in patients given induction therapy (17%) compared with standard therapy (6%, P = 0.053). Sustained biochemical and virological responses were 20%, 27%, and 17% in groups 1, 2, and 3, respectively. Platelet and leukocyte counts decreased following daily high-dose treatment and remained low until therapy cessation (P < 0.001). The data suggest that daily s.c. induction with 10 MU IFNalpha-n1 followed by intermittent or continuous maintenance therapy for 1 year does not improve the results achieved with the standard 1-year IFNalpha course in the treatment of chronic hepatitis C patients.     

High-level induction of gamma interferon with various mitogens in mice pretreated with Propionibacterium acnes.

Various T-cell mitogens induced high levels of circulating gamma interferon (IFN-gamma) in mice that had been pretreated with Propionibacterium acnes. Administration of lipopolysaccharide, a B-cell mitogen, to these mice also caused pronounced production of IFN-gamma in addition to IFN-alpha and IFN-beta. The enhanced induction was most marked at about 1 week after the pretreatment.     

A randomized controlled trial of high-dose maintenance interferon therapy in chronic hepatitis C

In chronic hepatitis C virus (HCV) infection, the rate of sustained response to interferon is low. We evaluated, in patients responding to a 26-week course of interferon, the effect of high-dose maintenance therapy in preventing relapse. Three hundred and ten patients with chronic HCV infection (38.3% with cirrhosis, 80.6% with HCV type 1) received interferon alfa-2b for 26 weeks (10 MU tiw for 8 weeks, then 5 MU tiw for 18 weeks). One hundred and twenty-four subjects (40%) normalized aminotransferases, and were allocated randomly either to continue on 5 MU tiw for a further 26 weeks (prolonged therapy group: 60 patients) or to stop interferon (brief therapy group: 64 patients). Fifty-two weeks after stopping interferon the overall sustained biochemical response rate was 13.2% (41/310). The number of patients with normal aminotransferases was comparable between the prolonged and brief therapy groups (30% vs. 35.9%, P = n.s.), and the rate of HCV-RNA clearance was similar (48.8% vs. 42.4%, P = n.s.). The timing of posttreatment relapse was not influenced by the duration of therapy. Fifty-nine patients (19%) did not complete therapy due to adverse effects. Multivariate analysis identified four features predicting sustained biochemical response in subjects normalizing aminotransferases under therapy: negative HCV-RNA at end of therapy, normal aminotransferases at 4 weeks of therapy, high baseline aminotransferases, and high baseline platelets. Infection with HCV type 1 was not a significant predictor of response, due to its high prevalence in our population (80.6%). It is concluded that in patients with chronic hepatitis C mostly infected by HCV type 1, a prolonged high-dose interferon course (900 MU over 52 weeks) did not increase the rate of sustained biochemical response and of HCV-RNA clearance in comparison to a brief course (510 MU over 26 weeks). J Med Virol 51:17–24, 1997. © 1997 Wiley-Liss, Inc.     

Co-infection by serologically-silent hepatitis B virus may contribute to poor interferon response in patients with chronic hepatitis C by down-regulation of type-I interferon receptor gene expression in the liver

Intrahepatic mRNA levels of type-I interferon (IFN) receptor genes have been shown to correlate with the clinical efficacy of IFN therapy in patients with chronic hepatitis C. Recently, co-infection by serologically-silent hepatitis B virus (HBV) has been assumed to be associated with the poor IFN response in patients with chronic hepatitis C. The aim of this study was to investigate the relationship between the co-infection of serologically-silent HBV and type-I IFN receptor gene expression in the liver of patients with chronic hepatitis C. The intrahepatic mRNA levels of IFNAR2, one of the two subunits of the type-I IFN receptor, were quantified and compared with both the prevalence of HBV DNA and the hepatitis C virus (HCV) genotype in 45 patients with chronic hepatitis C, who were negative for hepatitis B surface antigen. Co-infection, as evaluated by a nested polymerase chain reaction, was present in 22 patients (48.9%), with dominance of the HCV genotype 1b (65.2%) over genotype 2a (31.8%). Co-infection was associated with lower IFNAR2 mRNA levels, higher levels of serum HCV RNA, and a poor IFN response, regardless of the HCV genotype. The findings suggest the possibility that co-infection by serologically-silent HBV is one of the factors that can lead to an unfavorable IFN response in chronic hepatitis C by down-regulation of IFN receptor gene expression in the liver.     

Impaired response to alpha interferon in patients with an inapparent hepatitis B and hepatitis C virus coinfection

Summary.  The possibility of hepatitis B virus (HBV) infection in HBsAg-negative patients has been shown. However, an “inapparent” coinfection by HBV in hepatitis C virus (HCV)-positive patients generally is not taken into account in clinical practice. Mechanisms responsible for resistance to interferon (IFN) have not been completely clarified. The aim of this study was to investigate whether an “inapparent” coinfection by HBV in anti-HCV-positive chronic liver disease patients may influence IFN response. Fourteen anti-HCV positive, HBsAg-negative but serum HBV DNA-positive patients by PCR and 111 anti-HCV-positive, HBsAg-negative and HBV DNA (PCR)-negative patients with chronic hepatitis were treated with 3 MU of recombinant α-2a IFN 3 times weekly for 12 months. Serum HBV DNA and HCV RNA were determined before treatment, after 6–12 months and in coincidence with ALT flare-up by PCR. HBV PCR was performed using primers specific for the S region of the HBV genome and HCV PCR with primers localised in the 5′NC region of HCV genome. IgM anti-HBc was tested using IMx Core-M Abbott assay. By the end of treatment, ALT values had become normal in 4/14 HBV DNA-positive patients (28%), but all “responders” (4/4) relapsed between 2 and 5 months after therapy. All but one patient were HCV RNA-positive before treatment, 6 were also both HBV DNA and HCV RNA-positive during ALT flare-ups. In 5 patients, only HBV DNA and in 3 patients, only HCV RNA was detected when transaminase values increased. All patients remained HBsAg-negative and anti-HCV-positive. IgM anti-HBc was detected both before treatment and during ALT elevation in 3 patients and only during ALT relapse in 3 others. Of the 111 anti-HCV positive, HBsAg-negative and HBV DNA (PCR)-negative patients with chronic hepatitis, a biochemical response to IFN treatment was observed in 54% of the cases. Relapse of ALT values was observed in 47% of the cases during a follow-up of 1 year after treatment. “Inapparent” HBV/HCV coinfection may be implicated in cases of resistance to IFN treatment. In addition, HBV replication may persist in patients in whom HCV replication was inhibited by IFN treatment. The pathogenic role of HBV in liver disease was confirmed by detection of IgM anti-HBc in some cases; the appearance of these antibodies only after IFN treatment suggests that IFN may exert a selective role in favour of HBV. Further studies will show the effect of different treatment schedules. HBV DNA and/or IgM anti-HBc detection with very sensitive methods may be important both as a prognostic factor and as a tool for better understanding interviral relationships and mechanisms involved in multiple hepatitis virus infections.     

Analysis of hepatitis B virus genotypes and pre-core region variability during interferon treatment of HBe antigen negative chronic hepatitis B

The clinical importance of hepatitis B virus (HBV) genome variability has been reported recently. One example is the occurrence of hepatitis B virus pre-core mutants, which arise during spontaneous or interferon-induced seroconversion from HBeAg to anti-HBe and are thought to be selected by immune pressure. A survey of HBV pre-core mutants and viral genotypes in 35 HBeAg negative patients during interferon therapy was carried out to understand viral pathogenesis in this form of chronic hepatitis B. Seventeen patients responded to interferon therapy as assessed by the sustained normalization of serum ALT levels and the significant decrease of viremia levels. The response rate to interferon was independent of both initial serum viral DNA level and interferon doses. During interferon therapy, a significant decrease of M0 (wild-type pre-core sequence at pos. 1887–1908), M1 (TGG to TAG at pos. 1896) or M2 (TGG to TAG at pos. 1896, and GGC to GAC at pos. 1899) positive viral genomes was found in 48%, 42%, and 33% of patients, respectively. A higher response rate to interferon therapy was observed in patients infected with HBV genotype A (70%) or M0 positive strains (75%) as compared to patients infected with genotype D/E (40%) or M1/M2 positive strains (44%). The data support the hypothesis that pre-core defective HBV represent viral mutants with an increased capacity to resist exogenous alpha interferon. These findings emphasize that characterization of HBV genome variability prior to interferon therapy may help to predict antiviral response in HBeAg negative patients. © 1996 Wiley-Liss, Inc.     

TT virus infection in patients with chronic hepatitis B or C: influence on clinical, histological and virological features

Concomitant infection with TT virus and hepatitis B virus (HBV) or hepatitis C virus (HCV) is common. However, the effect of TTV infection on chronic hepatitis B or C is unknown. The prevalence of TTV infection, the effect of TTV infection on the clinical, histological and virological features of patients with chronic hepatitis B or C, and the influence of TTV infection on the HCV response to interferon alfa therapy were studied. A total of 100 asymptomatic hepatitis B surface antigen carriers, 220 patients with HBV-related chronic liver diseases, and 110 patients with chronic hepatitis C treated with interferon alfa (3 million units subcutaneously three times a week for 24 weeks) were enrolled. Serum HCV RNA and serum TTV DNA were detected by the polymerase chain reaction (PCR). Serum HBV DNA and serum HCV RNA level were quantified by branched DNA assays. Infection with TTV was detected in 21.5% of HBV carriers and 37% of HCV carriers. TTV infection had little effect on the clinicopathological course of chronic HBV infection. In chronic hepatitis C, clinical features, histological severity, serum HCV RNA levels, and the response to interferon alfa therapy did not differ between those with and without TTV infection. The loss of serum TTV DNA did not correlate with the biochemical response as did in the loss of serum HCV RNA. In conclusion, TTV infection is found frequently in patients with chronic hepatitis B or C in Taiwan; however, coinfection with TTV does not affect the clinicopathological course of chronic hepatitis B or C and the response to interferon alfa therapy.     

Human interferon alfa therapy and hepatitis B virus markers in the serum of patients with chronic course of illness

Dynamics of serum levels of HBsAg, HBeAg and anti HBc were followed during human interferon alpha (Hu IFN alpha) therapy of patients with chronic active or chronic persistent hepatitis B. More or less expressed oscillations of HBsAg serum levels seen in two out of our six treated patients seemed to occur due to IFN effect. Little and seldom changes were observed in HBeAg and anti HBc serum levels. The profiles of HBsAg serum levels of interferon-treated patients compared with the profiles of "conventionally" treated patients disclosed occurrence of spontaneous or perhaps interferon-induced cyclic elevations and depressions of HBsAg blood levels. The possible significance of this phenomenon is discussed.     

Evaluation of the natural killer cell-interferon system in patients with mid-gut carcinoid tumours treated with leucocyte interferon.

Nine patients with mid-gut carcinoid tumours received leucocyte interferon (IFN) i.m. daily for 90 days. Six patients clearly ameliorated in symptoms typical of the carcinoid syndrome (flushing, diarrhoea, asthma) which correlated with reduced serum levels of tumour related polypeptides and urinary output of 5-hydroxyindole acetic acid (5-HIAA). Before IFN treatment, peripheral blood mononuclear leucocytes (PBLs) from carcinoid patients showed markedly deficient production of pH 2 labile IFN-alpha in response to Staphylococcus aureus Cowan I (SACoI) in vitro. In contrast, IFN-alpha responses to the inducers Sendai virus and beta-haemolytic streptococcus group G and IFN-gamma responses to Lens culinaris lectin and concanavalin A were normal. Also, basal and in vitro IFN enhanced natural killer (NK) cell activity and T cell mitogen-induced cell proliferation were similar in patients and controls. During 90 days of IFN therapy, SACoI-induced IFN responses became entirely undetectable. There were transient declines at 1 and 30 days in IFN responses to the other IFN inducers, of mitogen-induced lymphocyte proliferation and of basal NK activities. The increments of NK cell activities after in vitro IFN exposure were clearly decreased in IFN treated patients, suggesting in vivo activation of these cells. Thus, the results demonstrate one remarkable abnormality in carcinoid patients: a deficient IFN response to SACoI and a clear influence of IFN therapy on several parameters of the IFN-NK system.