Long-term effects of mass screening for neuroblastoma in infancy

Eighty-four neuroblastoma patients were treated at the Department of Pediatrics, Kyoto Prefectural University of Medicine, during the 27 years from 1962 to 1988. They were divided into three groups: 35 cases in phase 1, the 12 years before mass screening from 1962 to 1974; 22 in phase 2, the 8 years after the onset of mass screening by a qualitative vanillylmandelic acid (VMA) test from 1974 to 1982; and 27 in phase 3, the recent 6 years from 1983 to 1988, after the introduction of mass screening by quantitative assay for VMA and homovanillic acid using high performance liquid chromatography. The clinical findings of these patients were compared for each phase. In Kyoto, the number of annual neuroblastoma cases diagnosed under 1 year of age increased from 0.58 in phase 1 to 1.50 in phase 2 and 3.17 in phase 3. The number of cases over 2 years of age decreased from 2.00 in phase 1 to 0.88 in phase 2 and 1.00 in phase 3. Survival rates increased from 17.1% (six of 35) in phase 1 to 54.5% (12 of 22) in phase 2 and 85.2% (23 of 27) in phase 3. The annual number of neuroblastoma deaths decreased from 2.42 in phase 1 to 1.25 in phase 2 and 0.67 in phase 3. Mass screening for neuroblastoma in infancy has increased the long-term survival rates of neuroblastoma cases treated at this hospital.

[A mechanical study on new ceramic crowns and bridges for clinical use]

By the recent development of new ceramics, i.e. castable glass ceramics and high strength porcelain, the clinical use of all-ceramic bridges as well as all-ceramic crowns have been expected. The purpose of this study was to evaluate the mechanical properties of new ceramics and to analyze the stress distributions in new ceramic crowns and bridges. The Young's modulus, flexural strength and diametral tensile strength of four types of new ceramics (DICOR, BIORAM-C, OPTEC, and HI-CERAM) were measured, and the fracture loads of new ceramic anterior crowns and bridges on the metal abutments were evaluated. Three dimensional finite element analyses of new ceramic anterior crowns and bridges were also carried out to investigate the effects of various mechanical factors; locations of loading point, types of ceramics, thickness of crowns, luting materials, core materials, and designs of fixed joints. In each experiment, the loading forces were applied at 45 degree to the tooth axis. The results were summarized as follow; 1) DICOR showed the highest flexural strength. HI-CERAM hard core porcelain showed the highest Young's modulus and tensile strength. 2) HI-CERAM crowns showed the highest fracture load among the new ceramic crowns. DICOR bridges were significantly stronger than BIORAM-C bridges. The stress analyses of the experimental cases indicated that the fractures of crowns and bridges occurred by the concentration of tensile stresses. 3) By the load at the incisal edge, the highest tensile stresses were caused in the crown. In the crown with 0.5 mm thickness at axial wall, high tensile stresses were observed at more wide regions of palatal side than in the crown with 0.75 mm or 1 mm thickness. However, in the case with an enamel layer remained on the surface of the abutment tooth, the stresses were reduced in spite of the crown thickness. When the abutment tooth was restored with a metal post and core, the stresses of the crown decreased in comparison with the natural abutment tooth. 4) In case of bridges, high tensile stresses concentrated at the fixed joints under any loading point. The stresses tended to rise slightly according to the increase of the Young's modulus of bridges. The aluminous core material which had high Young's modulus was effective for the reduction of the stresses at the surface of the bridge. Those tensile stresses were reduced remarkably by increasing the thickness of the fixed joints toward the labial and vertical side.(ABSTRACT TRUNCATED AT 400 WORDS)

[Evaluation of mica crystal glass ceramic crown marginal fitness]

The purpose of this study is to investigate the influence of three marginal shape of abutment teeth (Flat, Moderate and Steep) on the fitness of castable glass ceramics (DICOR) crown clinically. The following results were obtained: 1. The change of width of three marginal shapes showed the same tendency on each firing procedure. 2. The vertical change of three marginal shapes showed the most constant on Flat and decreased on Steep. 3. On the marginal edge, the Labiopalatal gaps were larger than Mesiodistal gaps. 4. On Labiopalatal section, the gaps of Steep were larger than those of Flat and Moderate especially as cast. 5. The gaps Flat were almost same on Labial, Palatal, Mesial and Distal parts.

Purification of staphylococcal exfoliative toxin by high pressure liquid chromatography

Exfoliative toxin (ET) isolated from a clinical strain of Staphylococcus aureus was purified to homogeneity, using a 3-step HPLC system. NH2-terminal 20 amino residues of purified ET was found to be identical with ETA of S. aureus TA (7), S. aureus TC16 (9) and S. aureus ZM (10), but stability of purified ET was completely different from that of ETA. This purification system gave a high yield of pure ET, which exhibited higher purity than specimens purified by more complicated and time-consuming procedures. It is useful for small-scale purification for the comparative study of ET and easy to scale up for preparative purification.

Particle design of tolbutamide by the spherical crystallization technique. III. Micromeritic properties and dissolution rate of tolbutamide spherical agglomerates prepared by the quasi-emulsion solvent diffusion method and the solvent change method

With the objective of modifying the micromeritic properties of tolbutamide (i.e., to manufacture a highly functional powder form), particle design was attempted using a quasi-emulsion solvent diffusion (QESD) method, and the micromeritic properties and dissolution rate of the obtained spherical agglomerates were evaluated by comparison with agglomerates prepared by the solvent change (SC) method. For the production of tolbutamide agglomerates by the QESD method, a necessary condition was the addition of a sucrose fatty acid ester to the system as an emulsifying agent. The particle diameter of the agglomerates obtained by the QESD method depended on the size of the initially formed quasi-emulsion droplets, which in turn depended on the viscosity of the solution. In addition, the agglomerates were nearly perfectly spherical in shape. In the QESD method, the quasi-emulsion droplets crystallized instantaneously from the droplet surface inward. The resultant agglomerates were dense, had great mechanical strength and showed excellent flowability due to their perfect spherical shape. On the other hand, the agglomerates produced by the SC method were conglomerates of primary crystals, and fine, needle-like crystals formed on their surface. As a result, these agglomerates had a large specific surface area, and they therefore showed greater solubility than the agglomerates prepared by the QESD method.

Epithelial regeneration in collagen-coated and uncoated patch grafts implanted into dog tracheas

The paper compares ultrastructural regeneration of the tracheal epithelium on patch grafts coated or not coated with collagen. A longitudinal patch window 2 x 1 cm (four cartilaginous rings in cephalocaudal extent) was made on the ventral wall of the cervical trachea in dogs, and replaced by a polypropylene Malex mesh graft. Grafts coated with collagen allowed normal connective tissue ingrowth and subsequent epithelial spreading. From the cut edge, flat, stratified, poorly differentiated cells migrated and spread on the newly formed stroma. Six weeks after the operation, the prosthesis was thoroughly covered by pseudostratified ciliated columnar epithelium with a newly formed basal lamina. On uncoated grafts, in contrast, some regenerated ciliated cells formed compound cilia or irregular microvilli and dilated endoplasmic reticulum. At 6 weeks, no normal basal cells differentiated, although some bizarre flat cells with extremely extended cytoplasm were located in the basal area of the epithelium. The basal lamina was thick and discontinuous. The underlying stroma included abnormally elongated fibroblasts with condensed cytoplasm and curved, randomly dispersed collagen fibrils. These ultrastructural results indicate that (1) regenerated epithelial cells were derived from poorly differentiated cells; (2) a plastic implant may lead to abnormal regeneration in the connective tissues and epithelium; and (3) collagen coating of the graft may allow fibroblasts to produce normal connective tissue substances.

Insolubilization of apatite-collagen composites by UV irradiation

The physico-chemical properties and biocompatibility of insolubilized apatite-collagen composites were examined. A carbonate-containing hydroxyapatite with chemical composition and crystallinity similar to that of bone was synthesized at pH 7.4 and 60 degrees C. The apatite powder was mixed with collagen solution, whose antigenicity had been removed by enzymatic treatment and formed into apatite-collagen pellets. After insolubilization by UV irradiation for 4 h, the composites showed remarkably reduced disintegration and showed good biocompatibility when implanted into rat abdomen.

Diverse responses to retinoid in morphological differentiation, tumorigenesis and N-myc expression in human neuroblastoma sublines

We established the subline RT-BMV-C6 from the parent human neuroblastoma cell line RT-BM by a process that required repeated subculture of cells, which were prone to disaggregation. RT-BMV-C6 and the parent cloned line, RT-BM-1, had an identical marker chromosome, confirming that both lines were derived from a common progenitor. In the analysis of surface antigen expression, RT-BMV-C6 did not react with UJ-127-11, Leu7 or KP-NAC2 MAbs to which RT-BM-1 showed positive binding. The levels of both N-myc amplification and expression in RT-BMV-C6 were twice as high as the level obtained in RT-BM-1. Colony-forming efficiency in soft agar was 2.0 +/- 0.8% for RT-BMV-C6 and 3 times greater than that for RT-BM-1 (0.6 +/- 0.1%). When 100 x 10(6) cells of RT-BM-1 and RT-BMV-C6 were inoculated into nude mice, tumor incidence was significantly higher for RT-BMV-C6 (6/6; 100%) than for RT-BM-1 (0/6; 0%). Our data show that N-myc is closely related to tumorigenicity in NB. When RT-BM-1 and RT-BMV-C6 were co-cultured with a new synthetic retinoid, polyprenoic acid (E5166), and dibutyryl cyclic AMP, RT-BM-1 was induced to neuronal differentiation, defined by the formation of neuronal processes and expression of neurofilaments, whereas RT-BMV-C6 was not. However, when exposed to E5166, N-myc expression of RT-BMV-C6 was more strongly reduced than that of RT-BM-1, and colony formation of RT-BMV-C6 was significantly inhibited as compared to RT-BM-1. These findings suggest that the reduction of N-myc expression might closely correlate with growth inhibition accompanying neuronal differentiation of neuroblastoma cells.

[Development of ultrasound laryngography and its phonetic significance]

A new laryngeal imaging system, namely, ultrasound laryngography, has been developed. Vocal fold vibration in M-mode image can be obtained by adjusting the cursor line to the desired level of the vocal fold in B-mode image. In addition, waveforms obtained by M-mode, variant M-mode, pulse transmission and other method can be recorded simultaneously. (1) Simultaneous recording of M-mode, variant M-mode and pulse transmission method during phonation. Seven male adults of unknown vocal pathology were asked to phonate the vowel /e/ and vocal fold vibration was recorded by ultrasound laryngography. Two types of M-mode image of the free margin were obtained. In one type, M-mode image recorded at the upper part of the vocal fold was found to be bright in the closed and opening phase and was displayed as ascending lines from the closed to opening phase. In the other type, M-mode image recorded at the lower part was bright in the closing and closed phase and was displayed as convex curves. Open quotients were measured by pulse transmission method at the upper, middle and lower part of the vocal fold, respectively. The mean value at the middle part was the smallest among the three parts. In waveforms obtained by variant M-mode method of the upper and lower part of the vocal fold, a negative peak was found in the closing and opening phase, respectively. (2) Observation of vocal attack. Vibration mode of three types of vocal attack was investigated by ultrasound laryngography with simultaneous recording of air flow rate using a constant-temperature, hot wire anemometer. i) Hard attack: by M-mode and pulse transmission method, the glottis remained closed until vocal fold vibration is initiated. Air leakage was not observed before the beginning of vocal fold vibration. ii) Soft attack: the glottis was slightly open and air flow rate was gradually increasing before vocal fold vibration is initiated. iii) Breathy attack: the glottis was widely open and a considerable air leakage was observed prior to the initiation of vocal fold vibration. iv) Among all vocal attacks investigated, changes in the variant M-mode waves were observed before the beginning of phonation, suggesting that minute movements of the surface are initiated before the onset of vocal fold vibration.

Nipradilol, a beta-adrenoceptor antagonist having a vasodilatory action, attenuates myocardial acidosis induced by coronary artery occlusion in dogs

In dogs anesthetized with pentobarbital, the anterior descending coronary artery (LAD) was partially occluded to reduce LAD flow to about half of the original flow (partial occlusion). Myocardial pH (MpH) was measured by the use of a micro glass pH electrode. MpH decreased from 7.5-7.63 to 6.82-6.86 30 min after partial occlusion of the LAD. Nipradilol (0.3 mg/kg) was injected intravenously 30 min after partial occlusion, which continued for a further 60 min after nipradilol injection. Nipradilol decreased blood pressure and heart rate, and significantly increased myocardial pH which had been decreased by partial occlusion, within 60 min after injection. Nipradilol-induced restoration of the myocardial [H+] (calculated from the pH data), that had been increased by partial occlusion, was 48.5%. Bradycardia induced by nipradilol was not a determinant factor in the pH effect of nipradilol, because even in the paced heart, nipradilol restored the myocardial [H+] that had been increased by partial occlusion. These results indicate that nipradilol attenuates ischemia-induced myocardial acidosis, suggesting the favorable effect of nipradilol on ischemic myocardium. The favorable effect of nipradilol may be due to the beta-adrenoceptor antagonistic effect rather than the vasodilating effect.

[Disintegration of visible light-cured composite resins caused by long-term water immersion]

The purpose of this study is to clarify a cause of disintegration of composite resins by long-term immersion in distilled water. Three kinds of visible light-cured composite resins (Heliosit, Plurafil Super and Visio Dispers) and one conventional composite resin (Clearfil F II) were prepared as the specimens with a 20 mm diameter and 1 mm thickness. These specimens were immersed in distilled water at 37 +/- 1 degree C for 3 years. These specimens were analysed and observed by a comprehensive multi analyzer and scanning electron microscope. The other hand residues in distilled water were analysed by infrared (IR) and nuclear magnetic resonance (NMR) spectrometers. The surface layer of all four composite resins showed signs of disintegration. The composite resins with abundant dissolved substances had disintegrated markedly, and such disintegration occurred deep inside the specimens. In IR and 1H-NMR spectra of dissolved substances, two visible light-cured composite resins (Heliosit and Plurafil Super) could be detected unreacted monomers, but one visible light-cured composite resin (Visio Dispers) and one conventional composite resin (Clearfil F II) could not be detected them. In 1H-NMR spectra of dissolved substances of all four composite resins, new signals not composed originally were observed. The progress of disintegration were demonstrated clearly. The dissolved substances were shown as the disintegrated substance between resin matrixs and silane coupling agents. It is suggested that the disintegration of composite resins by long-term water immersion is derived from hydrolysis.

Differential susceptibility of HLA class II antigens induced by gamma-interferon in human neuroblastoma cell lines

Five neuroblastoma cell lines have been examined for the induction of HLA class II antigens by a recombinant gamma-interferon. The expression of HLA-DR and -DP was induced on up to 80% of cells in two of five neuroblastoma cell lines examined (KP-N-SI and KP-N-RT). Low expression of HLA-DR and -DP was induced on the SK-N-DZ line in the presence of recombinant gamma-interferon for 10 days. In contrast HLA-DQ was not induced on any of five neuroblastoma cell lines studied. HLA-DR and -DP antigen induction was reversible, falling to nondetectable levels when interferon was removed from the culture medium. The reinduction of interferon to the culture medium again induced HLA-DR and -DP antigen expression in a fashion similar to that originally observed. These results were confirmed by Northern blot analysis using a probe to HLA-DR alpha mRNA. Recombinant interferon appears to induce HLA class II expression at the level of gene transcription or posttranscription. The results also indicate that HLA-DR, -DP, and -DQ antigens are independently regulated. Treatment of neuroblastoma cell lines with gamma-interferon results in the induction of a differentiated phenotype. Although the cytokine gamma-interferon induces neurofilament expression in some of the cell lines, this was not the case for all lines studied. Thus no correlation could be established between the morphological differentiation and either HLA class II or neurofilament expression. In addition, no correlation between response to recombinant interferon and N-myc amplification was noted. The biological significance of HLA class II expression on neuroblastoma cell lines by gamma-interferon may be related to the differentiation stage of neuroblastoma cells or may enable gamma-interferon-treated neuroblastoma cells to be recognized by cytotoxic T-cells.

Attenuation of ischaemia-induced regional myocardial acidosis by bevantolol, a beta 1-adrenoceptor antagonist, in dogs

In dogs anaesthetized with pentobarbital, the left anterior descending coronary artery (LAD) was occluded for 90 min. so that about 1/2 of the original flow was allowed to flow (partial occlusion). Bevantolol (a beta 1-adrenoceptor antagonist) or propranolol (a reference drug) was injected intravenously 30 min. after partial occlusion. Regional myocardial pH was measured by a micro glass pH electrode inserted in the LAD area. Partial occlusion decreased myocardial pH by 0.62 to 0.74. Bevantolol (1.0 mg/kg) or propranolol (1.0 mg/kg) significantly increased myocardial pH, that had been decreased by partial occlusion, within 60 min. after the injection. Restoration of myocardial [H+] (defined as return towards a lower [H+] to the preocclusion level) (calculated from the pH data) induced by bevantolol and that induced by propranolol were 64.0 and 66.4% (measured 60 min. after the injection), respectively. Bevantolol or propranolol decreased heart rate also. Even in the paced heart, bevantolol restored the myocardial [H+] that had been increased by partial occlusion. These results suggest that bevantolol has a favorable effect on the ischaemic myocardium as has propranolol, and that the pH effect of bevantolol is not primarily due to a decrease in heart rate.

Application of a local drug delivery system to periodontal therapy: I. Development of collagen preparations with immobilized tetracycline

For the purpose of applying a local drug delivery system to periodontal therapy, atelocollagen preparations with immobilized tetracycline (TC) were prepared by modifying the form of the collagen, the concentration of the immobilized TC, and the time of the cross-link process with glutaraldehyde. The course of the TC release from the collagen preparations into an aqueous solution was determined in relation to time. The preparations were also inserted into periodontal pockets, and the amount of TC remaining in the pocket was determined daily. The results obtained were as follows: 1) The degree of drug release could be controlled to some extent by adjusting the TC concentration and the time of the cross-link process; and 2) an amount of TC exceeding the effective dose in the gingival crevicular fluid was present in the periodontal pocket even 10 days after the insertion of TC fixed in the cross-linked processed collagen film in the periodontal pockets.

[Effects of cibenzoline on myocardial ischemia]

The effect of cibenzoline, an antiarrhythmic drug, on myocardial ischemia was studied in the anesthetized open-chest dog. Ischemia was induced by completely ligating or partially occluding the left anterior descending coronary artery. The levels of ATP and creatine-phosphate decreased, and the ADP and AMP levels increased during ischemia. The level of glycogen was also decreased, and that of lactate was increased by ischemia, resulting in myocardial acidosis. Pretreatment with either 2 mg/kg or 8 mg/kg of cibenzoline prevented the decrease in ATP level and the increase in lactate level. These results suggest that cibenzoline reduces the influence of ischemia on the myocardium.

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.

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.

Schwannian cell differentiation of human neuroblastoma cell lines in vitro induced by bromodeoxyuridine

In normal development the neural crest gives rise to sympathetic neuroblasts, sensory and autonomic ganglia, as well as Schwann cells. One tumor arising from this tissue is the neuroblastoma (NB), a malignancy of the adrenergic component of the sympathetic nervous system. Recent histological studies have shown that neuroblastomas can present with a schwannian cell component, rich in S100 protein. We have investigated the differentiation of NB cell lines, GOTO and RT-LN-1, into a schwannian cell phenotype using bromodeoxyuridine (BrdU). This agent induced morphological changes in these cell lines. Flat-epithelial cells were identified in the GOTO cell line and both flat-epithelial and neuronal phenotypes were found in the RT-LN-1 cell line. S100 protein (beta-Subunit) was induced in both cell lines after 18-25 days of BrdU treatment as determined by enzyme-linked immunoassay. In addition increase in the beta-subunit of S100 protein was identified in BrdU-treated flat-epithelial cells by indirect immunofluorescence using a monoclonal antibody specific for the beta-subunit of the protein. Cyclic nucleotide phosphodiesterase activity significantly increased in both BrdU-treated NB cell lines, as compared with nontreated cells. However no significant increase of glial fibrillary acidic protein in BrdU-treated cells was found either by enzyme-linked immunoassay or indirect immunofluorescence using a monoclonal antibody to glial fibrillary acidic protein. Thus, cells with Schwann cell characteristics can clearly be identified in the neuroblastoma cell lines after BrdU treatment. Fluorescence-activated cell sorting analysis revealed no quantitative changes in cell membrane antigens recognized by monoclonal antibodies UJ-13A (neuroectodermal associated antigen) and anti-Thy-1 (Thy-1) on BrdU treatment. In contrast, UJ-127-11 (neuroectodermal associated) decreased, and W6/32 and BB7.7 (HLA-ABC) and BBM.1 (beta 2-microglobulin) markedly increased in both BrdU-treated cell lines. No induction of L243 (HLA-DR), B7/21 (HLA-DP), and Genox 3.55 (HLA-DQ) was noted. The increased HLA-ABC (HLA class I) antigen may enable BrdU-treated NB cells to be recognized by cytotoxic T-cells. This may be related to the pathological evidence that NB patients whose tumors are rich in S100 protein have a better prognosis. Further studies on the potential of differentiation agents to induce a phenotypic change, that is associated with an improved prognosis for NB patients, are required.

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.

Cytotoxic T lymphocyte response to minor H-43a alloantigen in H-43b mice. Privileged H-2Kb restriction to the response is not due to immunodominance or epistatic effect but due to Ir gene function of H-2Kb itself

Previous study demonstrated that anti-H-43a cytotoxic T lymphocyte (CTL) response of H-43b CWB (H-2b) stain carrying non-major histocompatability complex (MHC) genes of C3H and F1 strains raised by crossing CWB with various H-43b strains was restricted exclusively by self H-2Kb (Kb). In the present study, newly produced C3W strain (H-2k, H-43b), which is H-43-congenic to C3H/HeN (H-2k, H-43a), was used as H-43b mice, and possibility of immunodominance of Kb was examined. No anti-H-43a CTL response could be induced in C3W strain and F1 strains raised by crossing C3W with other H-43b strains not carrying Kb. Thus, the possibility of immunodominance of Kb over the other MHC class I alleles could not be supported. We also examined possibility of epistatic effect of I region genes and non-MHC genes on the Kb restriction. (C3W x C57BL/6)F1(I-Ak/b) and (C3W x B6.CH-2bm12)F1(I-Ak/bm12)mice showed equally anti-H-43a CTL response restricted exclusively by self Kb, and (C3W x B10.MBR)F1(Ik/k) mice also showed anti-H-43a CTL response restricted solely by self Kb. Cold target competition experiments demonstrated that H-43b C57BL/10 or A.BY mice, which do not have non-MHC genes of C3H mounted anti-H-43a CTL response restricted solely by self Kb. Thus, no relation of I region genes or non-MHC genes to the Kb restriction was shown. All the results indicate that H-43b mouse strains, including F1, can not achieve anti-H-43a CTL response unless they carry Kb allele. Notably, (C3W x C57BL/6)F1 mice mounted self Kb-restricted anti-H-43a CTL response, whereas (C3W x B6.CH-2bm1)F1 mice carrying mutated Kb could not mount anti-H-43a CTL response at all. These findings indicate strongly that Kb itself is classical Ir gene of anti-H-43a CTL response and directs self Kb restriction of the response.