Hepatitis B surface antigen reduction by switching from long-term nucleoside/nucleotide analogue administration to pegylated interferon.

Hepatitis B surface antigen (HBsAg) reduction during nucleoside/nucleotide analogue (NA) therapy is slow and an alternative strategy for patients receiving ongoing NA to facilitate HBsAg reduction is required. We investigated whether switching to pegylated interferon (PEG-IFN) after long-term NA administration enhances HBsAg reduction. Forty-nine patients who switched from long-term NA to 48 weeks of PEG-IFN alfa-2a were studied. The mean duration of previous NA was 48 months (sequential group). A total of 147 patients who continued NA and matched for baseline characteristics were analysed for comparison (NA continuation group). The treatment response was defined as HBsAg reduction ≥1.0 logIU/mL at the end of PEG-IFN. HBsAg reduction at week 48 was 0.81±1.1 logIU/mL in the sequential group, which was significantly higher than that in the NA continuation group (0.11±0.3 logIU/mL, P < .001). The treatment response was achieved in 29% and 2% of the sequential group and NA continuation group (P < .001), and the odds ratio of sequential therapy for the treatment response was 19 compared with the NA continuation (P < .001). In patients tested positive for hepatitis B e antigen (HBeAg), HBeAg seroconversion was higher in the sequential group (44% vs 8%, P < .001). In HBeAg-negative patients, only patients in the sequential group achieved HBsAg loss. No patient needed to resume NA administration because of HBV DNA increase accompanied by alanine aminotransferase flares. In summary, sequential therapy with PEG-IFN after long-term NA enhances the reduction of HBsAg and may represent a treatment option to promote HBsAg loss.

ITPA genetic variants influence efficacy of PEG-IFN/RBV therapy in older patients infected with HCV genotype 1 and favourable IL28B type.

Inosine triphosphatase (ITPA) genetic variants are strongly associated with ribavirin (RBV)-induced anaemia during pegylated interferon (PEG-IFN) plus RBV therapy. However, the treatment efficacy of ITPA genetic variants has not been fully explored. We enrolled 309 individuals infected with hepatitis C virus genotype 1, who were treated with PEG-IFN plus RBV for 48 weeks. The ITPA SNP: rs1127354 and IL28B SNP: rs8099917 were genotyped. We examined the risk factors for severe anaemia up to week 12 after the start of treatment and treatment efficacy. The incidence of severe anaemia, ≥ 3 g/dL reduction or <10 g/dL of haemoglobin (Hb) up to week 12, was more frequent in patients with CC at rs1127354 [65% (145/224), 33% (73/224)] than in those with CA/AA [25% (21/85), 6% (8/85)] (P < 0.0001). ITPA genotype, pretreatment Hb level and age were independent predictive factors for severe anaemia: Hb < 10 g/dL. In IL28B favourable type, the sustained virologic response rate was higher in ≥ 60-year-old patients with CA/AA than in those with CC [71% (22/31) vs 40% (26/65), P = 0.005], although there was no significant difference in treatment efficacy according to ITPA genetic variants in the <60-year-old patients. The proportion of patients administered ≥ 80% of the dosage of RBV was significantly higher in the patients with CA/AA than in those with CC (P = 0.025), resulting in a lower relapse rate. In conclusion, ITPA genetic variants were associated with severe RBV-induced anaemia and could influence the efficacy of PEG-IFN plus RBV treatment among elderly patients with IL28B favourable type.

Mechanism of the dependence of hepatitis B virus genotype G on co-infection with other genotypes for viral replication.

Hepatitis B virus (HBV) is classified into several genotypes. Genotype G (HBV/G) is characterised by worldwide dispersion, low intragenotypic diversity and a peculiar sequence of the precore and core region (stop codon and 36-nucleotide insertion). As a rule, HBV/G is detected in co-infection with another genotype, most frequently HBV/A2. In a previous in vivo study, viral replication of HBV/G was significantly enhanced by co-infection with HBV/A2. However, the mechanism by which co-infection with HBV/A2 enhances HBV/G replication is not fully understood. In this study, we employed 1.24-fold HBV/A2 clones that selectively expressed each viral protein and revealed that the core protein expressing construct significantly enhanced the replication of HBV/G in Huh7 cells. The introduction of the HBV/A2 core promoter or core protein or both genomic regions into the HBV/G genome showed that both the core promoter and core protein are required for efficient HBV/G replication. The effect of genotype on the interaction between foreign core protein and HBV/G showed that HBV/A2 was the strongest enhancer of HBV/G replication. Furthermore, Western blot analysis of Dane particles isolated from cultures of Huh7 cells co-transfected by HBV/G and a cytomegalovirus (CMV) promoter-driven HBV/A2 core protein expression construct indicated that HBV/G employed HBV/A2 core protein during particle assembly. In conclusion, HBV/G could take advantage of core proteins from other genotypes during co-infection to replicate efficiently and to effectively package HBV DNA into virions.

Biochemical response to interferon therapy correlates with interferon sensitivity-determining region in hepatitis C virus genotype 1b infection.

Biochemical responders maintain normal alanine aminotransferase levels after interferon (IFN) therapy despite persistent presence of hepatitis C virus (HCV) RNA in their sera. There have been few reports on predictive factors for biochemical response. A region associated with sensitivity to IFN was identified in the nonstructural protein 5 A of genotype 1b [aa 2209-2248; IFN sensitivity-determining region (ISDR)]. The substitutions in ISDR correlate with sustained response to IFN. In this report, we assessed the association of ISDR with biochemical response. The sequences of ISDR were determined in 62 patients with HCV genotype 1b treated by IFN in two randomized controlled trials. 30 patients had wild ISDR (identical to HCV-J), 20 intermediate ISDR (1-3 amino acid substitutions compared with HCV-J), and 12 mutant ISDR (four or more amino acid substitutions). All 12 patients with mutant ISDR had a sustained response, while only one of those with wild or intermediate ISDR had a sustained response (P < 0.0001). In the 49 patients other than sustained responders, the patients with intermediate ISDR obtained biochemical response significantly more frequently (52.6%, 10/19) than those with wild-type ISDR (20.0%, 6/30) (P < 0.05). Multivariate analysis indicated the number of substitutions in ISDR as the most important predictor for biochemical response (discriminant coefficient=1.08, P < 0.05) and sustained response (discriminant coefficient=6.13, P < 0.0001). In phylogenetic analysis, clustering of sustained responders and biochemical responders was observed. These results demonstrate that the substitutions in ISDR are the most important predictor for biochemical response to IFN in patients infected with genotype 1b as well as for sustained response.

Randomized controlled trial of twice-a-day administration of natural interferon beta for chronic hepatitis C.

We conducted a randomized controlled trial to assess the efficacy of twice-a-day administration of natural interferon beta (IFNbeta) as an induction of IFN therapy for chronic hepatitis C. Seventy-one patients with chronic hepatitis C were enrolled into the trial and randomly assigned into three treatment groups. Six million units (MU) of IFNbeta were administered once-a-day for the first 4 weeks, and then thrice weekly for 12 weeks in 20 patients (once-a-day group). Three milion units of IFNbeta were administered twice-a-day for the first 2 weeks, 6 MU once-a-day for the next 2 weeks, and then thrice weekly for 12 weeks in 23 patients (twice-a-day+beta group), or 6 MU of lymphoblastoid IFNalpha were administered thrice weekly for the last 12 weeks instead of IFNbeta in 28 patients (twice-a-day+alpha group). Four patients in once-a-day group (20%), 9 in twice-a-day+beta group (39%), and 12 in twice-a-day+alpha group (43%) obtained sustained response. Sustained response rate in twice-a-day groups was higher than in once-a-day group, although there was no statistical significance. The present study suggested the possible superiority of twice-a-day administration of IFNbeta as an induction therapy to once-a-day administration, but further studies are needed to confirm this regimen.

Temporal expression of urokinase plasminogen activator, plasminogen activator inhibitor and gelatinase-B in chronic wound fluid switches from a chronic to acute wound profile with progression to healing.

The plasminogen activator/plasmin system is known to initiate a proteolytic cascade resulting in the activation of matrix metalloproteinases in vitro leading to the degradation of extracellular matrix. To investigate whether or not this cascade is present during delayed wound healing and contributes to the pathophysiological basis of impaired healing we examined the temporal expression of urokinase plasminogen activator, plasminogen activator inhibitor-1 and gelatinase-B in fluid collected from chronic venous leg ulcers compared to acute surgical mastectomy wounds. Using a chromogenic substrate assay, levels of active urokinase plasminogen activator in chronic wounds were found to be about five fold higher compared to sera and two fold higher compared to mastectomy wounds. Levels of active plasminogen activator inhibitor-1 in chronic wounds were four times higher than those found in sera and two times higher than those found in mastectomy wound fluid. Using a fibrin overlay system and reverse zymography, we found that when the wound was not healing, the expression of urokinase plasminogen activator in chronic wound fluid was initially detected in the active forms (50 and 33 kDa), but that as the wound healed and decreased in size, was detected as an inhibitor- bound urokinase plasminogen activator-plasminogen activator inhibitor-1 complex ( congruent with 80-116 kDa). When the expression of active urokinase plasminogen activator was highest, no plasminogen activator inhibitor-1 was detectable. In contrast, urokinase plasminogen activator was always detected in the inhibitor bound form as a urokinase plasminogen activator-plasminogen activator inhibitor-1 complex in blood- and plasma-derived serum and mastectomy wound fluid. Plasminogen activator inhibitor-1 was detected in blood-derived serum and mastectomy wound fluid but not in plasma derived serum. Expression of matrix metalloproteinase-9 in chronic wound fluids, analyzed by gelatin zymography, showed that when urokinase plasminogen activator was detected in the active forms, matrix metalloproteinase-9 was overexpressed by approximately twice that found in mastectomy wounds and approximately 30 times that detected in blood-derived sera. When urokinase plasminogen activator appeared almost entirely as an enzyme- inhibitor complex, the level of expression of matrix metalloproteinase-9 was similar to that seen in mastectomy wound fluid. We conclude that the switch in urokinase plasminogen activator expression from an active to inhibitor bound form correlates with the decrease seen in matrix metalloproteinase-9 expression suggesting the presence of a proteolytic cascade initiated by the plasminogen activator/plasmin system during wound healing leading to the activation of matrix metalloproteinase-9. In addition, expression of urokinase plasminogen activator and matrix metalloproteinase-9 appear to be useful biomarkers to determine clinical wound healing status.

Randomized controlled trial of lymphoblastoid interferon alpha for chronic hepatitis C (comparison of 9-MU and 6-MU doses). IFN Treatment Group of Affiliated Hospitals of the Third Department of Internal Medicine at Nagoya University School of Medicine.

OBJECTIVE: We conducted a randomized controlled trial to compare the efficacy of two different dosages of lymphoblastoid interferon alpha (IFN) for the treatment of chronic hepatitis C. METHODS: Eighty-four patients with chronic hepatitis C were enrolled and randomly assigned into the two groups; group A was treated with 6 million units (MU) and group B with 9 MU daily for the first 2 wk, and then thrice weekly for an additional 14 or 22 wk. RESULTS: Eighty patients were evaluated (39 patients in group A and 41 in group B); 14 patients in group A (35.9%) and 15 in group B (36.6%) obtained sustained response. The percentages of patients who became negative for HCV RNA at the end of the second wk differed slightly between the groups, without statistical significance (56.4% and 68.3%). When assessed in detail, patients with genotype 1 and < 1 Meq/ml of viral load became negative for HCV RNA significantly more frequently in group B (eight of eight) than in group A (three of seven) (p < 0.05) at the end of the second week, whereas the sustained response rate was similar between the groups (five of eight and four of seven). Predictors of sustained response by multivariate analysis were low viral load (< 1.0 Meq/ml) and negativity of HCV RNA at the end of the second wk of IFN. CONCLUSIONS: The results indicated that there was no difference in sustained response rate between the 6-MU and 9-MU doses. The earlier disappearance of HCV RNA, at the end of the second wk or at least by the end of the fourth week, is an essential condition for sustained response.

Percutaneous transhepatic balloon dilation for papillary stenosis.

In this study, a case of primary common bile duct stone due to papillary stenosis is reported. The patient was a 68-year-old man with complaints of epigastric pain and fever who had undergone gastrectomy at age 55 and cholecystectomy with choledocholithotomy at age 62. Laboratory data revealed elevation of the transaminases acid biliary enzymes. Both abdominal ultrasonography and CT scan revealed dilatation of the common bile duct with stones. Since endoscopic retrograde cholangiopancreatography could not visualize the bile duct, percutaneous transhepatic biliary drainage was carried out. After lithotripsy by percutaneous transhepatic cholangioscopy a diagnosis of papillary stenosis was made following percutaneous transhepatic manometry of the sphincter of Oddi, and balloon dilatation through the PTBD fistula was successfully performed. In this case report, emphasis is placed on the diagnosis and treatment of papillary stenosis.

Changes in serum hepatitis C virus RNA titer and response to interferon therapy in patients with chronic hepatitis C.

Response to interferon (IFN) therapy for chronic hepatitis C has been determined by the alteration of serum alanine aminotransferase (ALT) values. However, eradication of hepatitis C virus (HCV) could be another aim of the therapy. Thus, we serially measured serum HCV RNA levels during therapy and for at least 12 months after cessation of therapy in 65 patients with chronic hepatitis C who received IFN-alpha (49 cases) or -beta (16 cases). The presence of HCV and its amount were measured by the combination of nested and competitive PCR. Twenty-seven patients, who were categorized as complete responders, showed sustained normalization of ALT values for more than six months posttreatment. The viral RNA titers at pretreatment were significantly lower in complete responders (logarithmic copy numbers/ml: 5.4 +/- 1.3, P < 0.001) than in partial and nonresponders. Complete response rate was significantly higher in patients with HCV genotype III (68.4%, P < 0.01) than those with type II (23.6%). Among 27 complete responders, HCV RNA became undetectable in only 13 patients six months after completion of therapy, and 11 still had low levels of viremia; however, none experienced relapse of the disease during follow-up of 12-24 months. Three complete responders showed lasting high-titered viremia, and their ALT values rose again during follow-up. Our data suggest that IFN treatment of chronic hepatitis C is often ineffective in eradicating HCV infection even in responders, and long-term follow-up study is necessary to determine the sustained beneficial effect of IFN.

Interferon-gamma production specific for hepatitis B virus antigen by intrahepatic T lymphocytes in patients with acute and chronic hepatitis B.

OBJECTIVES: Studies were undertaken to determine whether intrahepatic lymphocytes have a greater cellular immune response specific for hepatitis B virus (HBV) antigen than peripheral blood lymphocytes in HBV-infected man. METHODS: HB nucleocapsid antigen-stimulated interferon-gamma (IFN-gamma) production of lymphocytes was measured in acute self-limited hepatitis (AH) (eight cases) and chronic hepatitis (CH) (14 cases). RESULTS: In both patient groups, basal IFN-gamma levels without any stimulation were higher in the hepatic T cells than in the peripheral T cells. The values in cultures from blood and liver were larger in AH than in CH. Alternatively, IFN-gamma response to HBcAg and HBeAg was less in hepatic T cells than in the corresponding blood cultures; T cell response was HLA class II restricted. Cell flow cytometry study showed that in all patient groups, percentages of CD3+, CD8+, and HLA-DR+ cells were significantly greater in liver than in peripheral blood, whereas the proportion of hepatic CD4+ cells was decreased, compared with that in peripheral CD4+ cells. CONCLUSIONS: These findings suggest that liver infiltrates are already activated in vivo to produce IFN-gamma, particularly in patients with AH. The changes in the proportion of lymphocyte subsets may be responsible for the altered IFN-gamma response of hepatic T cells.

Long-term carriage of hepatitis C virus with normal aminotransferase after interferon treatment in patients with chronic hepatitis C.

Studies were undertaken to investigate whether interferon therapy could induce hepatitis C virus (HCV) carriage with normal serum alanine aminotransferase (ALT) values using an assay that combined reverse transcription and polymerase chain reaction. The subjects studied were 53 patients with chronic active hepatitis C who received interferon (alpha, 33 cases; beta, 20 cases) therapy. All were seropositive for HCV RNA prior to therapy. In all 22 complete responders, whose ALT levels fell to normal during therapy and for at least 24 weeks after therapy, HCV RNA became persistently negative except in two cases. The two had sustained viremia on treatment and for 1.0-1.5 years of follow-up, although their biochemical tests were normal. In 15 patients with a transient response in whom the disease recurred when interferon was stopped, HCV RNA was undetectable in 80% of the cases at the end of therapy, but the virus reappeared with subsequent elevation of ALT in all patients. However, 3 patients in this group had normal enzyme levels with viremia for 2.1-2.8 years of follow-up after acute deterioration of illness. In 16 patients who did not respond to interferon, HCV RNA was persistently positive during and after therapy. These findings suggest that interferon therapy induces a long-term carrier state of HCV infection with normal ALT levels in some patients.

Effects of interferon-alpha treatment on hepatitis B virus antigen-specific immunologic responses in patients with chronic hepatitis B.

Studies were undertaken to evaluate the relationship between the immune responses and the effectiveness of interferon-alpha treatment in 21 patients with HBeAg-positive chronic active hepatitis. Peripheral blood mononuclear cells (PBMC), obtained on four occasions during an 8-week course of IFN-alpha therapy, were cultured with recombinant HBcAg, purified HBeAg or pokeweed mitogen (PWM). During follow-up for 6 months after therapy, clearance of serum HBeAg was observed in eight patients designated as responders. Immunological responses of PBMC obtained before treatment did not differ between responders and non-responders. In responders, IFN-gamma and anti-HBc production was depressed during therapy, but recovered to above the pretreatment level at the end of and/or after cessation of therapy, while lymphocyte proliferation was enhanced during therapy with a subsequent decline to baseline value. In non-responders, such changes were modest throughout the study, and anti-HBc response remained decreased even after cessation of therapy. These results indicate that PBMC of responders have immunologically different responses to IFN-alpha therapy when compared with non-responders.

Localisation of intrahepatic interleukin 6 in patients with acute and chronic liver disease.

AIM: To evaluate the role of local interleukin 6 (IL-6) in the pathogenesis of acute and chronic liver disease. METHODS: The cellular site of IL-6 in cryostat sections of liver from 31 patients with liver disease was examined using indirect immunofluorescence with a monoclonal antibody. RESULTS: IL-6 staining in sinusoidal endothelial cells was very noticeable and diffusely distributed in the lobules of specimens of acute viral hepatitis. IL-6 expression in endothelial cells, particularly in necrotic areas of hepatocytes, was increased and was accompanied by enhanced expression in Kupffer cells. In contrast, IL-6 staining in infiltrating mononuclear cells was prominent in portal tracts, and the numbers of cytokine positive cells were greater in specimens of chronic active hepatitis compared with chronic persistent hepatitis. In non-specific reactive hepatitis intrahepatic expression of IL-6 was minimal, while in alcoholic liver fibrosis the cytokine distribution in the lobules was similar to that of acute viral hepatitis. CONCLUSIONS: These results indicate that locally produced IL-6 contributes to the inflammatory process and immunological response in acute and chronic liver disease.

Comparisons of peripheral blood and hepatic lymphocyte subpopulations and interferon production in chronic viral hepatitis.

Studies were undertaken to clarify the immunological mechanism in patients with chronic hepatitis C compared with chronic hepatitis B. Phenotypic study by flow cytometry showed that CD8+ T cells and HLA-DR+ cells isolated from liver biopsy specimen were significantly increased in their proportions as compared with those in peripheral blood, while intrahepatic CD4+ T cells were significantly lower than peripheral blood CD4+ T cells in both types of patients with chronic active hepatitis (CAH). Furthermore two-color analysis revealed that CD8+ CD11- and CD3+ HLA-DR+ cells were significantly elevated in liver tissue than in peripheral blood in both patients groups. In in vitro tests, mononuclear cells obtained from the liver of type B and type C CAH had a reduced capacity to produce IFN-gamma in response to pokeweed mitogen, while they produced equal amounts of IFN-alpha under stimulation with Newcastle disease virus as compared with control peripheral blood mononuclear cells. In contrast, spontaneous productions of both IFNs were greater in liver infiltrates of the two patients groups. These results indicate that functionally activated T cells are distributed in a similar manner in the liver of both chronic hepatitis B and C, suggesting that cytotoxic T cell plays a major role in the hepatocellular injury of both groups of patients.

Recombinant human alpha-interferon therapy for chronic non-A, non-B hepatitis: second report.

Four million units per day of recombinant human alpha-interferon were administered three times weekly for 16 wk to 26 patients with chronic non-A, non-B hepatitis. The efficacy of therapy was assessed by comparing it with the results in the nontreated patients, or with our previous study in which we administered 2 million units per day of interferon. The treatment was discontinued in four patients 8 wk after start of therapy because there was no improvement in serum aminotransferase levels. The remaining 22 patients completed the treatment schedule, and their aminotransferase values showed significant decreases throughout the therapy and during the follow-up period, compared with their baseline levels or the nontreated group. After 3 months of follow-up, normal aminotransferase activities were seen in eight treated patients. In four of these patients, liver histology showed a marked improvement in inflammation and parenchymal cell necrosis. Percent change from pretreatment level of serum 2',5'-oligoadenylate synthetase activity was significantly higher in the aminotransferase-normalized group than in the nonnormalized group during therapy. The present study suggested that a higher dose of alpha-interferon could control the disease activity more effectively in patients with chronic non-A, non-B hepatitis.

Pilot study of recombinant human alpha-interferon for chronic non-A, non-B hepatitis.

Recombinant human alpha-interferon was administered to 15 patients with chronic non-A, non-B hepatitis as a part of a pilot study. Patients received injections of 2 million units per day of interferon three times weekly for 16 wk. The treatment schedule was completed in all but one, whose serum aminotransferase levels were continuously elevated during treatment. In seven of the 15 patients, elevated serum aminotransferase levels decreased rapidly during therapy and eventually fell into the normal or nearly normal range. However, once the therapy was stopped, a prompt return of aminotransferase levels to pretreatment values usually was observed. After 3 months of follow-up, aminotransferase activities remained normal in only two patients in whom liver histology showed marked improvement in intralobular degeneration and focal necrosis of hepatocytes. Anti-interferon antibody was detected in four patients at the end of therapy, and decreased 2',5'-oligoadenylate synthetase activity occurred in two patients and in another with relapsed aminotransferase level. Whether alpha-interferon therapy could control the disease activity in patients with chronic non-A, non-B hepatitis deserves further evaluation in a prospective controlled trial.

Cytotoxic T lymphocyte responses to minor H-43 alloantigens in H-43a and H-43b mice. Both anti-H-43b and anti-H-43a CTL activities are generated exclusively in the context of the same H-2Kb restriction element.

We have previously demonstrated that anti-H-43a CTL response of H-43b responder mice was exclusively restricted by self H-2Kb (Kb) but not by the other nine self MHC class I alleles from independent origins, i.e., Kbml,d,k,s and Db,d,k,q,s. In the present study, we verified that Kf,q,r and Df,r alleles could also not serve as restricting class I elements in the CTL response to H-43a alloantigen. Another notable observation made in the earlier study was the fact that, in H-43 incompatibility of the alternative combination, H-43a mice were incapable of generating CTL activity against H-43b alloantigen. However, by means of employing new in vivo immunization procedures, we discovered that some but not all genetically identical H-43a responder mice could mount anti-H-43b CTL response restricted by self Kb. Again, no anti-H-43b CTL activity could be generated in the context of self Kk, Kj, Db or Dk molecules. Although the number of class I alleles we examined is still limited, these results indicate that antigenic fragments derived from the processed H-43a and H-43b alloantigens possess an indistinguishable epitope (agretope), and that such agretope either interacts only with the privileged Kb molecules or allows to bestow the immunogenic conformation of allodeterminants on the fragments solely in the context of the restricting Kb element.

Effector mechanism in rejection of allografts expressing an isolated minor histocompatibility disparity. Importance of cytotoxic T lymphocytes in the rejection of H-43a allografts by H-43b mice.

To explore effector mechanisms in allograft rejection, we transplanted skin grafts (SG) across a single minor histocompatibility locus (H-43) using mouse strains carrying the H-43b allele as SG recipients and those carrying the H-43a allele as SG donors. Recipients' spleen cells (SC) were assayed at various intervals for 200 days for anti-H-43a cytotoxic T lymphocyte (CTL) responsiveness, as well as delayed-type hypersensitivity (DTH) responsiveness. When H-43a SG from C3H.SW mice were transplanted to H-43b CWB mice, two thirds of the recipients rejected the SG, and recipients' SC showed marked self-H-2Kb-restricted anti-H-43a CTL responsiveness until the end of the observation period. In contrast,H-43aSG transplanted to H-43b (B10.BRxCWB)F1 (BWF1) mice survived in almost all of the BWF1 recipients. The anti-H-43a CTL responsiveness of the recipients' SC was evident until day 40 but thereafter started to wane and eventually disappeared. Notably, BWF1 mice whose self-H-2Kb-restricted anti-H-43a CTL precursors had been primed by prior injection with H-43a SC rejected H-2Kb-bearing H-43a CSW SG but not H-2k, H-43a C3H/HeN SG. In contrast, an anti-H-43a DTH response was not induced in any of the CWB and BWF1 recipients, including CWB recipients who rejected the H-43a SG. Since it has been well documented that anti-H-43a CTL are restricted solely by self-H-2Kb, the results in this study indicate that self-H-2Kb-restricted anti-H-43a CTL are responsible for rejection of H-43a allografts by H-43b recipient mice.