A validation study of combined resection and ablation therapy for multiple hepatocellular carcinoma.

AIM: To validate the utility of hepatic resection combined with complementary radiofrequency ablation (RFA) compared with resection alone for patients with multiple hepatocellular carcinoma (HCC), and to compare these results with those of a previous report. MATERIALS AND METHODS: A total of 78 HCC patients with multiple (≤5) tumours who were initially treated with hepatic resection only (Resection group) or with combined hepatic resection and RFA (Combination group) were included. Overall and disease-free survival were analysed. RESULTS: There were 21 women and 57 men with a median age of 72.5 (64.3-76.8) years. Fifty-three patients were treated with resection alone and 25 received combination therapy. The 3-, 5-, and 7-year cumulative overall survival rates were 81.2%, 68.2%, and 57.1%, respectively, in the Resection group, and 81.3%, 59.6%, and 42.4%%, respectively, in the Combination group (hazard ratio [HR], 1.462; 95% confidence interval [CI], 0.682-3.136; p=0.329). The 1-, 3-, and 5-year cumulative disease-free survival rates were 61.4%, 45.7%, and 39.8%, respectively, in the Resection group, and 53.1%, 18.6%, and 0%, respectively, in the Combination group (HR, 2.080; 95% CI, 1.157-3.737; p=0.014). The overall survival rate was not significantly different between the Resection and Combination groups in patients within the up-to-seven HCC criteria (n=56; HR, 2.101; 95% CI, 0.805-5.486; p=0.130) or those beyond these criteria (n=22; HR, 0.804; 95% CI, 0.197-3.286; p=0.761). CONCLUSIONS: The combination of hepatic resection and RFA therapy may be an effective strategy for HCC patients with multiple tumours.

Adhesion and friction between glass and rubber in the dry state and in water: role of contact hydrophobicity.

We study the contact mechanics between 3 different tire tread compounds and a smooth glass surface in water. We study both adhesion and sliding friction at low-sliding speeds. For 2 of the compounds the rubber-glass contact in water is hydrophobic and we observe adhesion, and slip-stick sliding friction dynamics. For one compound the contact is hydrophilic, resulting in vanishing adhesion, and steady-state (or smooth) sliding dynamics. We also show the importance of dynamical scrape, both on the macroscopic level and at the asperity level, which reduces the water film thickness between the solids during slip. The experiments show that the fluid is removed much faster from the rubber-glass asperity contact regions for a hydrophobic contact than for a hydrophilic contact. We also study friction on sandblasted glass in water. In this case all the compounds behave similarly and we conclude that no dewetting occur in the asperity contact regions. We propose that this is due to the increased surface roughness which reduces the rubber-glass binding energy.

Mechanism of increased microbial autofluorescence by heat treatment.

The total direct count (TDC) microbial enumeration method is rapid and suitable for analysing environmental samples containing numerous un-culturable micro-organisms. Conventional TDC methods require the addition of a fluorescent stain and are thus unsuitable for automatic monitoring. We unexpectedly found that heated micro-organisms emit strong autofluorescence. This study was conducted to determine how heating enhances the autofluorescence of bacteria and fungi and to evaluate whether the phenomenon could be exploited to develop a new TDC method. Bacterial autofluorescence was augmented by heating cells at 200°C. ELISA results indicated that levels of advanced glycation end products (AGEs) increased in heated microbes. Catechin, an inhibitor of the Maillard reaction, disrupted the intensification of autofluorescence. These results suggest that the enhanced autofluorescence is associated with the formation of AGEs and that the reaction could be utilized as alternative probe in TDC methods. SIGNIFICANCE AND IMPACT OF THE STUDY: Autofluorescence of bacteria and fungi was prominently intensified by heat treatment at 200°C. This phenomenon was associated with advanced glycation end products formed in micro-organisms via the Maillard reaction. The fluorescence signal was strong enough to be utilized as an alternative probe for fluorescent dye in the total direct count method. This phenomenon could be incorporated in an automatic apparatus for microbial enumeration, as it does not require staining.

Differences in background characteristics of patients with chronic hepatitis C who achieved sustained virologic response with interferon-free versus interferon-based therapy and the risk of developing hepatocellular carcinoma after eradication of hepatitis C virus in Japan.

We compared the background characteristics of patients with chronic hepatitis C who achieved eradication of hepatitis C virus (HCV), that is sustained virologic response (SVR), with interferon (IFN)-based versus IFN-free antiviral therapy in Japan. In addition, we used a previously reported risk assessment model to compare the incidence of hepatocellular carcinoma (HCC) after SVR by treatment type. Pretreatment characteristics of 1533 patients who achieved SVR with IFN-based therapy and 1086 patients with IFN-free therapy from five institutions across Japan were compared. The risk of HCC after SVR was assessed based on pretreatment characteristics, and the incidence of HCC after SVR was estimated in both groups. Age and serum alpha-fetoprotein levels were higher, platelet count was lower, and liver fibrosis was more advanced in patients who achieved SVR with IFN-free therapy compared with IFN-based therapy. The incidence of HCC after SVR in the IFN-free group was estimated to be more than twofold higher than in the IFN-based therapy group (7.29% vs. 3.09%, and 6.23% vs. 3.01% when excluding patients who have underwent curative treatment for HCC). There are large differences in pretreatment characteristics between patients who achieved SVR with IFN-based and IFN-free therapies in Japan, which are associated with differential risk of HCC after SVR. These differences can influence the incidence of HCC after SVR and should be taken into consideration when comparing IFN-based and IFN-free therapies in terms of hepatocarcinogenesis suppression with HCV eradication.

Characterization and application of newly developed polymorphic microsatellite markers in the Ezo red fox (Vulpes vulpes schrencki).

The Ezo red fox (Vulpes vulpes schrencki), a subspecies endemic to Hokkaido island, Japan, is a known host species for the tapeworm Echinococcus multilocularis. To develop tools for molecular ecological studies, we isolated 28 microsatellite regions from the genome of Ezo red fox, and developed 18 polymorphic microsatellite markers. These markers were characterized using 7 individuals and 22 fecal samples of the Ezo red fox. The number of alleles for these markers ranged from 1 to 7, and the observed heterozygosity, estimated on the basis of the genotypes of 7 individuals, ranged from 0.29 to 1.00. All markers, except DvNok5, were in Hardy-Weinberg equilibrium (P > 0.05), and no linkage disequilibrium was detected among these loci, except between DvNok14 and DvNok28 (P = 0.01). Moreover, six microsatellite loci were successfully genotyped using feces-derived DNA from the Ezo red fox. The markers developed in our study might serve as a useful tool for molecular ecological studies of the Ezo red fox.

Utility of the FIB-4 Index for hepatocarcinogenesis in hepatitis C virus carriers with normal alanine aminotransferase levels.

The FIB-4 index is a simple formula using age, aspartate aminotransferase, alanine aminotransferase (ALT) and platelet count to evaluate liver fibrosis. We investigated the ability of the FIB-4 index for hepatocarcinogenesis in hepatitis C virus (HCV) carriers with normal ALT levels. A total of 516 patients with ALT levels persistently at or below 40 IU/L during an observation period of over 3 years were included. Factors associated with the development of HCC were determined. Hepatocellular carcinoma (HCC) developed in 60 of 516 patients (11.6%). The incidence rate of HCC at 5 and 10 years was 2.6% and 17.6%, respectively. When patients were categorized according to the FIB-4 index as ≤ 2.0 (n = 226), >2.0 and ≤ 4.0 (n = 169), and > 4.0 (n = 121), the cumulative incidence of HCC at 5 years was 0.5%, 1.3% and 8.0%, respectively, and 2.8%, 25.6% and 37.1% at 10 years, respectively. Patients with FIB-4 index >4.0 were at the highest risk (P < 0.001). Factors that were significantly associated with HCC in the multivariate analysis were FIB-4 index >2.0 (hazard ratio (HR), 7.690), FIB-4 index >4.0 (HR, 8.991), α-fetoprotein (AFP) >5 ng/mL (HR, 2.742), AFP >10 ng/mL (HR, 4.915) and total bilirubin >1.2 mg/dL (HR, 2.142). A scoring system for hepatocarcinogenesis that combines the FIB-4 index and AFP predicted patient outcomes with excellent discriminative ability. The FIB-4 index is strongly associated with the risk of HCC in HCV carriers with normal ALT levels.

Biomarker-based prognosis in hepatocellular carcinoma: validation and extension of the BALAD model.

BACKGROUND: The Japanese 'BALAD' model offers the first objective, biomarker-based, tool for assessment of prognosis in hepatocellular carcinoma, but relies on dichotomisation of the constituent data, has not been externally validated, and cannot be applied to the individual patients. METHODS: In this Japanese/UK collaboration, we replicated the original BALAD model on a UK cohort and then built a new model, BALAD-2, on the original raw Japanese data using variables in their continuous form. Regression analyses using flexible parametric models with fractional polynomials enabled fitting of appropriate baseline hazard functions and functional form of covariates. The resulting models were validated in the respective cohorts to measure the predictive performance. RESULTS: The key prognostic features were confirmed to be Bilirubin and Albumin together with the serological cancer biomarkers, AFP-L3, AFP, and DCP. With appropriate recalibration, the model offered clinically relevant discrimination of prognosis in both the Japanese and UK data sets and accurately predicted patient-level survival. CONCLUSIONS: The original BALAD model has been validated in an international setting. The refined BALAD-2 model permits estimation of patient-level survival in UK and Japanese cohorts.

A gender-specific analysis of association between hyperuricaemia and cardiovascular events in patients with coronary artery disease.

BACKGROUND AND AIMS: Gender-related differences in the association between hyperuricaemia and cardiovascular events remain poorly understood. The objective of this study was to assess gender-related differences in the association between hyperuricaemia and cardiovascular events in patients with coronary artery disease (CAD). METHODS AND RESULTS: This study included 13,273 patients with CAD. Hyperuricaemia was defined as a plasma uric acid >7.0mgdl(-1) in men and >5.7mgdl(-1) in women. The primary outcome was 1-year all-cause mortality. Hyperuricaemia was found in 3745 men (36.5%) and 1562 women (50.3%); odds ratio (OR)=1.76, 95% confidence interval (CI) 1.62-1.91; P<0.001. Women with hyperuricaemia were older, had higher proportions of patients with diabetes and arterial hypertension and had reduced renal function and higher C-reactive protein levels compared with men with hyperuricaemia. One-year all-cause mortality was 9.3% (n=143) in women with hyperuricaemia versus 6.9% (n = 252) in men with hyperuricaemia (P=0.002). After adjustment in multivariable Cox proportional hazards model, uric acid predicted 1-year mortality with an adjusted hazard ratio (HR)=1.17, 95% CI (1.03-1.31), P=0.012 in men and HR=1.25, 95% CI (1.06-1.48), P=0.007 in women, for each standard deviation increase in the natural logarithm. Uric acid predicted 1-year mortality with an area under the receiver-operating characteristic curve=0.625, 95% CI (0.594-0.656) in men and 0.676, 95% CI (0.635-0.717) in women (P=0.044, for women versus men). CONCLUSION: Hyperuricaemia predicts an increased risk of 1-year mortality in both genders with a stronger association in women. Differences in cardiovascular risk profile may explain the stronger association between hyperuricaemia and cardiovascular events in women.

Restenosis in bare metal and drug-eluting stents: distinct mechanistic insights from histopathology and optical intravascular imaging.

An increasing body of evidence points to the existence of important differences in the processes of restenosis following drug-eluting stent (DES) as compared to bare metal stent implantation. Preclinical investigation and human autopsy studies have shown that the high efficacy of DES in comparison with bare metal stents in preventing restenosis is achieved at the collateral cost of a delay in healing of the stented arterial segment. Moreover bare metal stent restenosis is typically characterised by a homogeneous tissue rich in smooth muscle cells; whereas DES restenosis is more often hypocellular and proteoglycan-rich. In addition, in-stent neoatherosclerosis appears to have an accelerated course in DES. Angiographic surveillance studies show that while neointimal formation peaks six months after bare metal stenting, neointimal formation after DES therapy is temporally right shifted and remains a dynamic ongoing process (late luminal loss creep) even out to five years. The widespread availability of high resolution optical coherence tomography (OCT) is affording better understanding of the pathophysiology of in-stent restenosis. While bare metal stent restenosis is characterized by predominantly homogenous high-signal tissue echogenicity, layered pattern or heterogeneous tissue composition is more common in DES restenosis. Moreover, preliminary data suggests that tissue attenuation may increase in a time-dependent manner. Nevertheless, the paucity of direct histopathological correlation studies means that the tissue composition of these lesions remains speculative. Data from specifically designed imaging-pathology correlation studies in suitable preclinical models of restenosis and in autopsy specimens is eagerly awaited. Furthermore, although long-term longitudinal clinical follow-up is necessary to define the clinical relevance of optical imaging findings, the nature of restenosis as a disease entity means that its natural history is often altered by a mandate for repeat intervention directly following data acquisition.

Atezolizumab plus bevacizumab versus lenvatinib or sorafenib in non-viral unresectable hepatocellular carcinoma: an international propensity score matching analysis.

BACKGROUND: A growing body of evidence suggests that non-viral hepatocellular carcinoma (HCC) might benefit less from immunotherapy. MATERIALS AND METHODS: We carried out a retrospective analysis of prospectively collected data from consecutive patients with non-viral advanced HCC, treated with atezolizumab plus bevacizumab, lenvatinib, or sorafenib, in 36 centers in 4 countries (Italy, Japan, Republic of Korea, and UK). The primary endpoint was overall survival (OS) with atezolizumab plus bevacizumab versus lenvatinib. Secondary endpoints were progression-free survival (PFS) with atezolizumab plus bevacizumab versus lenvatinib, and OS and PFS with atezolizumab plus bevacizumab versus sorafenib. For the primary and secondary endpoints, we carried out the analysis on the whole population first, and then we divided the cohort into two groups: non-alcoholic fatty liver disease (NAFLD)/non-alcoholic steatohepatitis (NASH) population and non-NAFLD/NASH population. RESULTS: One hundred and ninety patients received atezolizumab plus bevacizumab, 569 patients received lenvatinib, and 210 patients received sorafenib. In the whole population, multivariate analysis showed that treatment with lenvatinib was associated with a longer OS [hazard ratio (HR) 0.65; 95% confidence interval (CI) 0.44-0.95; P = 0.0268] and PFS (HR 0.67; 95% CI 0.51-0.86; P = 0.002) compared to atezolizumab plus bevacizumab. In the NAFLD/NASH population, multivariate analysis confirmed that lenvatinib treatment was associated with a longer OS (HR 0.46; 95% CI 0.26-0.84; P = 0.0110) and PFS (HR 0.55; 95% CI 0.38-0.82; P = 0.031) compared to atezolizumab plus bevacizumab. In the subgroup of non-NAFLD/NASH patients, no difference in OS or PFS was observed between patients treated with lenvatinib and those treated with atezolizumab plus bevacizumab. All these results were confirmed following propensity score matching analysis. By comparing patients receiving atezolizumab plus bevacizumab versus sorafenib, no statistically significant difference in survival was observed. CONCLUSIONS: The present analysis conducted on a large number of advanced non-viral HCC patients showed for the first time that treatment with lenvatinib is associated with a significant survival benefit compared to atezolizumab plus bevacizumab, in particular in patients with NAFLD/NASH-related HCC.

Rubber friction: comparison of theory with experiment.

We have measured the friction force acting on a rubber block slid on a concrete surface. We used both unfilled and filled (with carbon black) styrene butadiene (SB) rubber and have varied the temperature from -10 °C to 100 °C and the sliding velocity from 1 µm/s to 1000 µm/s. We find that the experimental data at different temperatures can be shifted into a smooth master-curve, using the temperature-frequency shifting factors obtained from measurements of the bulk viscoelastic modulus. The experimental data has been analyzed using a theory which takes into account the contributions to the friction from both the substrate asperity-induced viscoelastic deformations of the rubber, and from shearing the area of real contact. For filled SB rubber the frictional shear stress σ(f) in the area of real contact results mainly from the energy dissipation at the opening crack on the exit side of the rubber-asperity contact regions. For unfilled rubber we instead attribute σ(f) to shearing of a thin rubber smear film, which is deposited on the concrete surface during run in. We observe very different rubber wear processes for filled and unfilled SB rubber, which is consistent with the different frictional processes. Thus, the wear of filled SB rubber results in micrometer-sized rubber particles which accumulate as dry dust, which is easily removed by blowing air on the concrete surface. This wear process seams to occur at a steady rate. For unfilled rubber a smear film forms on the concrete surface, which cannot be removed even using a high-pressure air stream. In this case the wear rate appears to slow down after some run in time period.

Identification of lenvatinib prognostic index via recursive partitioning analysis in advanced hepatocellular carcinoma.

BACKGROUND: After the advent of new treatment options for advanced hepatocellular carcinoma (HCC), the identification of prognostic factors is crucial for the selection of the most appropriate therapy for each patient. PATIENTS AND METHODS: With the aim to fill this gap, we applied recursive partitioning analysis (RPA) to a cohort of 404 patients treated with lenvatinib. RESULTS: The application of RPA resulted in a classification based on five variables that originated a new prognostic score, the lenvatinib prognostic index (LEP) index, identifying three groups: low risk [patients with prognostic nutritional index (PNI) >43.3 and previous trans-arterial chemoembolization (TACE)]; medium risk [patients with PNI >43.3 but without previous TACE and patients with PNI <43.3, albumin-bilirubin (ALBI) grade 1 and Barcelona Clinic Liver Cancer stage B (BCLC-B)]; high risk [patients with PNI <43.3 and ALBI grade 2 and patients with PNI <43.3, albumin-bilirubin (ALBI) grade 1 and Barcelona Clinic Liver Cancer stage C (BCLC-C)]. Median overall survival was 29.8 months [95% confidence interval (CI) 22.8-29.8 months] in low risk patients (n = 128), 17.0 months (95% CI 15.0-24.0 months) in medium risk (n = 162) and 8.9 months (95% CI 8.0-10.7 months) in high risk (n = 114); low risk hazard ratio (HR) 1 (reference group), medium risk HR 1.95 (95% CI 1.38-2.74), high risk HR 4.84 (95% CI 3.16-7.43); P < 0.0001. The LEP index was validated in a cohort of 127 Italian patients treated with lenvatinib. While the same classification did not show a prognostic value in a cohort of 311 patients treated with sorafenib, we also show a possible predictive role in favor of lenvatinib in the low risk group. CONCLUSIONS: LEP index is a promising, easy-to-use tool that may be used to stratify patients undergoing systemic treatment of advanced HCC.

Nonalcoholic steatohepatitis in hepatocarcinoma: new insights about its prognostic role in patients treated with lenvatinib.

BACKGROUND: Hepatocellular carcinoma (HCC) treatment remains a big challenge in the field of oncology. The liver disease (viral or not viral) underlying HCC turned out to be crucial in determining the biologic behavior of the tumor, including its response to treatment. The aim of this analysis was to investigate the role of the etiology of the underlying liver disease in survival outcomes. PATIENTS AND METHODS: We conducted a multicenter retrospective study on a large cohort of patients treated with lenvatinib as first-line therapy for advanced HCC from both Eastern and Western institutions. Univariate and multivariate analyses were performed. RESULTS: Among the 1232 lenvatinib-treated HCC patients, 453 (36.8%) were hepatitis C virus positive, 268 hepatitis B virus positive (21.8%), 236 nonalcoholic steatohepatitis (NASH) correlate (19.2%) and 275 had other etiologies (22.3%). The median progression-free survival (mPFS) was 6.2 months [95% confidence interval (CI) 5.9-6.7 months] and the median overall survival (mOS) was 15.8 months (95% CI 14.9-17.2 months). In the univariate analysis for OS NASH-HCC was associated with longer mOS [22.2 versus 15.1 months; hazard ratio (HR) 0.69; 95% CI 0.56-0.85; P = 0.0006]. In the univariate analysis for PFS NASH-HCC was associated with longer mPFS (7.5 versus 6.5 months; HR 0.84; 95% CI 0.71-0.99; P = 0.0436). The multivariate analysis confirmed NASH-HCC (HR 0.64; 95% CI 0.48-0.86; P = 0.0028) as an independent prognostic factor for OS, along with albumin-bilirubin (ALBI) grade, extrahepatic spread, neutrophil-to-lymphocyte ratio, portal vein thrombosis, Eastern Cooperative Oncology Group (ECOG) performance status and alpha-fetoprotein. An interaction test was performed between sorafenib and lenvatinib cohorts and the results highlighted the positive predictive role of NASH in favor of the lenvatinib arm (P = 0.0047). CONCLUSION: NASH has been identified as an independent prognostic factor in a large cohort of patients with advanced HCC treated with lenvatinib, thereby suggesting the role of the etiology in the selection of patients for tyrosine kinase treatment. If validated, this result could provide new insights useful to improve the management of these patients.

Epitopes associated with the MHC restriction site of T cells. II. Somatic generation of Iat epitopes on T cells in radiation bone marrow chimeras.

We described in this paper systematic alterations in the expression of unique I region controlled epitopes on helper T cells (Th) in chimeras according to the changes in their H-2 restriction specificity. Taking advantage of the reactivity of monoclonal antibodies (anti-Iat) putatively specific for the epitopes indirectly controlled by I region and expressed in association with the Iak restriction site of Th, we examined the alterations of these epitopes on Th cells from various bone marrow chimeras. Iatk epitopes were physiologically expressed on Iak-restricted but not on Iab-restricted Th cells in (H-2k X H-2b)F1 mice. In the chimeric condition, the H-2k-restricted Th of B6----F1 chimera acquired the expression of Iatk even though B6 Th is unable to express Iatk when developed under the physiologic condition. Iatk are also found on Th of fully allogeneic chimera of B6----C3H, whereas Th cells of C3H----B6 completely lost the Iatk expression. These results indicate that Iat epitopes originally defined as unique I region-controlled determinants selectively expressed on T cells are not encoded by the I region genes but are associated with the T cell receptor that sees the self Ia. The epitopes undergo the adaptive alterations according to the acquisition of a new MHC restriction. This is the first example to demonstrate the epitope associated with T cell receptor which undergo the systematic adaptive differentiation.

Properties of antigen-specific suppressive T-cell factor in the regulation of antibody response of the mouse. I. In vivo activity and immunochemical characterization.

An antigen-specific suppressive T-cell factor was extracted from physically disrupted thymocytes and spleen cells of mice that had been immunized with soluble protein antigens. The factor, when inoculated into syngeneic normal mice, could induce a significant suppression of IgG antibody response against a hapten coupled to the carrier protein by which the donor of the suppressor factor was immunized. The suppressor factor was found only effective in suppressing the antibody response of syngeneic or H-2 histocompatible recipients. The suppressive T-cell factor was removed by absorption with immunoadsorbent composed of the relevant antigen, but not with any of those of anti-immunoglobulin antibodies. The factor was successfully removed by alloantibodies with specificity for the K end (H-2K, I-A and I-B) of the H-2 complex of the donor strain, but not by those for the D end (I-C, SsSlp, and H-2D). The activity was removed by absorption with a heterologous antithymocyte serum. The mol wt of the suppression T-cell factor was between 35,000 and 60,000 as determined by Sephadex G-200 gel filtration. The suppressive T-cell factor was found to be a heat-liable protein.

Selective roles of thymus-derived lymphocytes in the antibody response. II. Preferential suppression of high-affinity antibody-forming cells by carrier-primed suppressor T cells.

Passive transfer of thymocytes and spleen cells from donors primed with keyhole limpet hemocyanin (KLH) caused significant decrease in the average avidity of anti-DNP antibodies produced by direct and indirect PFC in the recipients in both primary and adoptive secondary antibody responses against DNP-KLH. The analysis of the avidity distribution of antibodies produced by plaque-forming cells (PFC) indicated that the observed decrease in the average avidity is primarily due to the selective loss of high avidity subpopulation of PFC leaving low avidity subpopulation relatively unaffected. The degree of suppression in antibody avidity did not correlate with the reduction in the number of PFC, and thus causing the "shift" of avidity distribution of PFC to the low avidity end. These results indicate that the "maturation" of antibody in the T-cell-dependent antibody response is influenced by the carrier-specific suppressor T cells with respect to the emergence and selection of B cells having high affinity receptors for hapten. It is suggested that B cells binding antigen with high affinity receptors would be more easily affected than those with low affinity receptors by specific suppressor T cells which are capable of reacting the carrier portion of the same antigen.

Dual regulatory role of the thymus in the maturation of immune response in the rabbit.

Rabbits thymectomized in early adulthood produced more antihapten antibody than sham-thymectomized controls after hyperimmunization with 2,4-dinitrophenyl bovine gamma globulin (DNP-BGG). The average associated constant of anti-DNP antibody produced by thymectomized animals was more than 10 times higher than that of the controls. Similar effects were obtained by extensive treatment of rabbits with antithymocyte serum (ATS) before and during the immunization with DNP-BGG. The results indicated that relative diminution of thymus-derived lymphocytes (T cells) resulted in a stimulation of antibody-forming cells with a higher affinity. On the other hand, preimmunization of rabbits with different doses of BGG caused either enhancement or suppression of the hapten-specific antibody response, depending on the priming dose of BGG. The suppressed antibody response was always associated with a marked decrease in the antibody affinity. If rabbits were partially tolerized with a large dose of soluble BGG, some of the animals produced little antibody against hapten (DNP) coupled to this carrier, and the affinity of produced antibody was low. However, other rabbits tolerized with BGG produced large amounts of anti-DNP antibody upon hyperimmunization with DNP-BGG, whose affinity was only slightly lower than that of the control. These results can be harmonized if it is assumed that the thymus plays an important role in the maturation of the immune response. It is postulated that T cells, in numbers ordinarily available, would first assist in the proliferation of antihapten antibody-forming cell precursors already selected by antigen, thus accounting for the rapid increase of antibody affinity in the early stage of immunization. However, after a larger number of carrier-specific T cells are made in response to continued immunization, these would suppress antibody-forming cells. The suppression would be greater for cells with higher affinity for antigen, resulting in a decrease in antibody affinity. This postulate explains preferential stimulation and suppression of cells having higher affinity receptors under circumstances in which T cell are relatively depleted or overstimulated, and further permits an explanation for the decrease of antibody affinity after long-term immunization.

Selective roles of thymus-derived lymphocytes in the antibody response. I. Differential suppressive effect of carrier-primed T cells on hapten-specific IgM and IgG antibody responses.

Passively transferred thymocytes and spleen cells from donors primed with keyhole limpet hemocyanin (KLH) exerted differential suppressive effect on IgM and IgG antibody responses of syngeneic recipients immunized with DNP-KLH depending primarily on the time when KLH-primed cells were transferred. This was demonstrated by the decrease in the numbers of DNP-specific direct and indirect PFC in the spleen of the recipients given KLH-primed cells at different times during primary and secondary immunization. Whereas the cell transfer simultaneously with or 2 days after the primary immunization produced only slight suppression of the peak IgM antibody response, it caused profound suppression of late IgM and IgG antibody responses. By contrast, the cell transfer 3 days after the immunization produced immediate suppression of the ongoing IgM antibody response resulting in its earlier termination, while being unable to prevent the induction of IgG antibody response. KLH-primed cells could moderately suppress the secondary anti-DNP antibody response, in which IgG antibody response was found to be slightly more sensitive than IgM antibody response to the suppressive influence of KLH-primed cells. The suppressive effect of the KLH-primed spleen cells was completely eliminated by the in vitro treatment of the cells with anti-theta and C before cell transfer, indicating that cells responsible for the suppression are, in fact, T cells. The suppression of DNP-specific antibody response by KLH-primed T cells was achieved only if the recipients were immunized with DNP-KLH but not with DNP-heterologous carrier, suggesting that direct interaction between T and B cells is necessary for the suppression of the antibody response. It is concluded that susceptibility of B cells to the specific suppressive influence of T cells is inherently different depending on the differentiation stage of B cells and on the immunoglobulin class they are destined to produce.

Properties of the antigen-specific suppressive T-cell factor in the regulation of antibody response of the mouse. III. Dual gene control of the T-cell-mediated suppression of the antibody response.

The antigen-specific suppressive T-cell factor of mice, which had previously been shown to be an I region gene product, could effectively suppress the in vitro secondary antibody response of spleen cells from syngeneic or H-2 compatible mouse strains but not that of H-2 incompatible strains. The identities among genes in the left side half (K, I-A, and I-B) of the H-2 complex between the donor and recipient strains were found to be both necessary and sufficient for the induction of suppression. This suggests that the acceptor site for the suppressive T-cell factor is also determined by the gene present in the left side half of the H-2 complex. The cell type which expresses the acceptor site was found to be a subset of T cell. In general, the suppressive T-cell factor obtained from F1 mice could suppress the responses of both parental strains, and the parental factors could suppress the response of F1 mice. The results indicate that both suppressor and acceptor molecules are codominantly expressed on F1 T cells. There were found two types of defects in the expression of suppressor and acceptor molecules among mouse strains: A/J mice could not produce the suppressive T-cell factor despite that they could accept the factor produced by other H-2 compatible mouse strains. In contrast, all the B10 congeneic lines could produce the T-cell factor, but could not accept the factor produced by syngeneic and H-2 compatible non-B10 congeneic lines. The F1 hybrid of A/J and B10. A could both produce and accept the T-cell factor, and thus the expressions of suppressor and acceptor molecules were found to be dominant traits. These results indicate that the antigen-specific T-cell-mediated suppression is regulated by at least two genes both present in the H-2 complex, and that the complementation of these two genes is required for the induction of suppression.