Comparison of somatic mutation frequency among immunoglobulin genes

We analyzed the frequency of somatic mutation in immunoglobulin genes from hybridomas that secrete anti-(4-hydroxy-3-nitrophenyl)acetyl (NP) monoclonal antibodies. A high frequency of mutation (3.3-4.4%) was observed in both the rearranged VH186.2 and V lambda 1 genes, indicating that somatic mutation occurs with similar frequency in these genes in spite of the absence of an intron enhancer in lambda 1 chain genes. In contrast to the high frequency in J-C introns, only two nucleotide substitutions occurred at positions -462 and -555 in the 5' noncoding region in one of the lambda 1-chain genes and in none of the other three so far studied. Since a similar low frequency of somatic mutation was observed in the 5' noncoding region of inactive lambda 2-chain genes rendered inactive because of incorrect rearrangement, this region may not be a target or alternatively, may be protected from the mutator system. We observed a low frequency of nucleotide substitution in unrearranged V lambda 1 genes (approximately 1/15 that of rearranged genes). Together with previous results (Azuma T., N. Motoyama, L. Fields, and D. Loh, 1993. Int. Immunol. 5:121), these findings suggest that the 5' noncoding region, which contains the promoter element, provides a signal for the somatic mutator system and that rearrangement, which brings the promoter into close proximity to the enhancer element, should increase mutation efficiency.

High prevalence of neutralizing activity to Helicobacter pylori cytotoxin in serum of gastric-carcinoma patients

Helicobacter pylori infection is causally related to chronic type-B gastritis, and may also be associated with an increased risk of gastric carcinoma. Vacuolating cytotoxin, which is an 87-kDa protein secreted by H. pylori, induces eukaryotic cell vacuolation in vitro. To determine whether there is an association between H. pylori vacuolating cytotoxin and gastric carcinoma, we investigated several characteristics of H. pylori infection, i.e., isolation of H. pylori from gastric biopsies, antibodies specific for H. pylori, detection of neutralizing activity to vacuolating cytotoxin in serum and immunological detection of cytotoxin by serum. Out of 6 sera from gastric-carcinoma patients, all showed the neutralizing activity to vacuolating cytotoxin, in contrast to 3 of 5 sera from peptic-ulcer patients. Normal individuals showed no neutralizing activity. All sera possessing the neutralizing activity recognized an 87-kDa protein band by Western blot analysis. Our results confirmed that cytotoxin-neutralizing activity in human sera was associated with immunodetection of an 87-kDa protein. To further evaluate neutralizing activity in serum from gastric-carcinoma patients, we retrospectively analyzed frozen-stocked serum samples from 22 gastric-carcinoma patients. Sera from 21 of these 22 patients exhibited neutralizing activity. These sera were also checked for antibodies to H. pylori, using an ELISA; 16 sera showed positive results. Our results indicate that detection of cytotoxin-neutralizing activity in sera is strongly associated with H. pylori infection, and probably with gastric carcinoma, and is also of interest in the diagnosis of H. pylori infection.

Histological studies on the rheumatoid synovial membrane irradiated with a low energy laser

The beneficial effects of low energy laser irradiation on rheumatoid arthritis (RA) joints have been reported, but the mechanisms of action of low energy lasers in RA are unclear. The synovial membrane in cases of RA was studied histologically to observe the effects of low energy laser irradiation. Fourteen knee joints of RA cases, which had been scheduled for arthroplasty, were irradiated with a gallium-aluminium-arsenide (Ga-Al-As) laser (790 nm in wavelength and 10 mW of output power) prior to the surgical operation, at six points of the external aspect of the knee joint for 80 seconds at each points once a day for 6 days. On the day following the last irradiation, pieces of synovial membrane from the lateral irradiated area and from the median nonirradiated area as a control were resected during the arthroplasty. The histological findings of the irradiated synovial membrane showed flattening of epithelial cells, decreased villous proliferation, narrowed vascular lumen, and less infiltration of inflammatory cells compared with those of nonirradiated synovia. The evaluation of slides was done in a blinded manner, and significant differences was seen by Wilcoxon's t-test (P < 0.01). Histological findings suggested that the low energy laser irradiation induced suppression of inflammation in the synovial membrane of RA.

Purification of Gnathostoma spinigerum larval antigens by monoclonal antibody affinity chromatography

An immunoaffinity column was prepared by coupling a partially purified Gnathostoma spinigerum-specific IgG1, MAb SK-6C4 (5 mg/ml) to CNBr-activated Sepharose 4B. Ten milliliters of approximately 0.3 mg/ml of crude soluble G. spinigerum larval antigens (GsAL3) were loaded onto the affinity column at a flow rate of about 5 ml/hour. Elution of the bound antigens was accomplished using 50 mM diethylamine-HCI containing 0.15 M NaCL, pH 11.5. The average amount of eluted antigens obtained by one passage of crude GsAL3 (1-4 mg) through 4 to 8 ml of column matrix was 143 micrograms (range, 67 - 414 micrograms). The minimal amount of purified GsAL3 detectable by ELISA using MAb SK - 6C4 (100 micrograms/ml) was 50 ng/ml. The SK - 6C4 affinity-purified GsAL3 was found to be relatively pure and immunologically specific as determined by SDS-PAGE and Western blotting, respectively.

Neurosteroids in cerebrospinal fluid in neurologic disorders

In order to investigate the role of "neurosteroids" in the central nervous system (CNS), cerebrospinal fluid (CSF) levels of dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS) were determined by radioimmunoassay in 57 patients with various neurologic disorders and 26 patients with non-neurologic disorders. The content of CSF DHEA and DHEAS in patients with Guillain-Barré syndrome (GBS), and the content of CSF DHEAS in patients with carcinomatous meningitis were significantly higher as compared to non-neurological control patients. These changes may be explained by the breakdown of blood-nerve barrier in these disorders. A significant positive correlation was observed between DHEAS and total protein in CSF. In males but not females, a negative correlation was observed between CSF DHEAS and aging. The level of CSF DHEAS, but not DHEA, was significantly higher in males than in females.

Specific IgG autoantibodies are potent inhibitors of autoreactive T cell response to phytohemagglutinin-activated T cells

PHA-activated human T cells express MHC class II molecules and have been shown to stimulate autoreactive T cells in autologous mixed lymphocyte reaction (T-T AMLR). We now demonstrate that normal human serum can dramatically suppress the proliferative response in T-T AMLR. The inhibitory factor was detected in the IgG fraction, and the activity was found to be mediated through the F(ab')2 portion of the IgG molecule, implying that the inhibitor could be specific. All homologous as well as autologous sera tested contained the inhibitory activity. Human serum was also found to suppress allogenic MLR stimulated by PHA-activated T lymphocytes but not allogenic MLR stimulated by nonactivated PBMC, indicating that the mechanism of inhibition is related to PHA activation of the stimulator cells. Moreover, pretreatment of the PHA-activated T lymphocytes with human serum resulted in a significant inhibition of T-T AMLR, as opposed to pretreatment of nonactivated PBMC, indicating that PHA-activated stimulators are functionally involved in the inhibition. Cytofluorometric analysis revealed that autologous IgG specifically binds to PHA-activated T lymphocytes and not to nonactivated CD3+ T cells. Furthermore, serum absorbed by PHA-activated T lymphocytes substantially lost its inhibitory activity whereas serum absorbed by nonactivated PBMC did not, suggesting that a surface molecule(s) expressed during activation of the stimulator cells is involved in the inhibition. The addition of human serum later in the culture period (&gt; 3 days) resulted in a marked decrease in inhibition, implying that the presence of IgG in the early recognition phase of T-T AMLR is essential for maximum inhibitory effect. These results raise the possibility that natural autoantibodies present in normal human IgG may play an important role in regulating immune response mediated by autoreactive T cells.

Specific IgG autoantibodies are potent inhibitors of autoreactive T cell response to phytohemagglutinin-activated T cells

PHA-activated human T cells express MHC class II molecules and have been shown to stimulate autoreactive T cells in autologous mixed lymphocyte reaction (T-T AMLR). We now demonstrate that normal human serum can dramatically suppress the proliferative response in T-T AMLR. The inhibitory factor was detected in the IgG fraction, and the activity was found to be mediated through the F(ab')2 portion of the IgG molecule, implying that the inhibitor could be specific. All homologous as well as autologous sera tested contained the inhibitory activity. Human serum was also found to suppress allogenic MLR stimulated by PHA-activated T lymphocytes but not allogenic MLR stimulated by nonactivated PBMC, indicating that the mechanism of inhibition is related to PHA activation of the stimulator cells. Moreover, pretreatment of the PHA-activated T lymphocytes with human serum resulted in a significant inhibition of T-T AMLR, as opposed to pretreatment of nonactivated PBMC, indicating that PHA-activated stimulators are functionally involved in the inhibition. Cytofluorometric analysis revealed that autologous IgG specifically binds to PHA-activated T lymphocytes and not to nonactivated CD3+ T cells. Furthermore, serum absorbed by PHA-activated T lymphocytes substantially lost its inhibitory activity whereas serum absorbed by nonactivated PBMC did not, suggesting that a surface molecule(s) expressed during activation of the stimulator cells is involved in the inhibition. The addition of human serum later in the culture period (> 3 days) resulted in a marked decrease in inhibition, implying that the presence of IgG in the early recognition phase of T-T AMLR is essential for maximum inhibitory effect. These results raise the possibility that natural autoantibodies present in normal human IgG may play an important role in regulating immune response mediated by autoreactive T cells.

Elimination of HIV-infected cells by lymphocytes armed with a bifunctional antibody to gp120 of HIV and CD3

The T-cell receptor (TCR) can acquire a new antigen binding site by treatment with a bifunctional antibody (BFA) prepared with mAb against a specified antigen and an epitope of the TCR. Lymphocytes armed with BFA directed to CD3 and an HIV antigen were able to eliminate all HIV antigen-positive cells during incubation with a mixture of HIV-infected and uninfected cells. HIV antigen-positive cells even from persistently infected cells were undetectable with immunofluorescence staining although HIV genes were detectable by polymerase chain reaction (PCR) amplification indicating that only dormantly infected or low producer cells, if any, survived. This suggests that HIV antigen-positive cells could be eliminated by administration of BFA-armed lymphocytes leaving HIV patients with only dormantly infected or low producer cells.

Anterior sagittal anorectoplasty as a redo operation for imperforate anus

Based on the idea of transsphincteric approach by Peña, we applied anterior sagittal anorectoplasty (ASARP) as a redo operation in 10 patients, who present moderate to severe fecal incontinence postoperatively. Those patients exhibited anal opening located anteriorly to the center of contraction of external sphincter muscles. Operation is begun with making a circumferential skin incision in the mucocutaneous junction around the anal opening, extending posteriorly along the median line to the center of the external sphincter muscles. Upon confirming the vertical muscle and the external sphincter muscles, the rectal tube, being dissected free, is mobilized backward to be placed at the center of the vertical muscles and enclosed by the muscle. After the operation, an improvement was noted in either clinical symptoms or scores, being particularly marked for incontinence and staining scores. Anorectal manometry and barium enema studies also showed a significant improvement. These results provide ample justification of ASARP as a redo operation for imperforate anus being worthwhile trying in properly selected patients with poor anorectal function following the primary operation.

[Allergic granulomatosis and angiitis associated with intestinal perforation and eye movement disorder]

A perforation in the small intestine and one and a half syndrome were observed in 45-year-old male with allergic granulomatosis and angiitis (AGA). The patient was first admitted to our hospital in 1988 with complaints of bronchial asthma and an abnormal density on his chest X ray. The diagnosis of PIE syndrome was made based on marked peripheral blood eosinophilia. He was successfully treated with prednisolone and had been well on the maintenance therapy of small doses of it. In May 1990, peripheral neuropathy occurred in his bilateral lower legs and it was followed by nausea and vomiting. The laboratory findings on admission showed leukocytosis (19,300/mm3) with 43% eosinophilia and elevated blood level of IgE (3000 IU/ml). On the tenth day of admission, ileus symptom and subsequently a perforation of the small intestine were observed. The mesenterial specimens obtained during the emergency operation showed the findings compatible with AGA. Remission of AGA was induced by the treatment with 60 mg prednisolone and 100 mg cyclophosphamide per day following methylprednisolone pulse therapy. He was well on maintenance prednisolone until June 1991, when he suddenly developed one and a half syndrome. Although cranial CT scan and MRI showed no abnormal findings, cyclophosphamide therapy was resumed and prednisolone was increased because microangiopathy due to AGA was thought to be the cause of this central nervous system symptom. The one and a half syndrome improved with this therapy. This case suggests that the long term treatment with prednisolone and cyclophosphamide would be indicated in the severe AGA with close monitoring of the symptoms and peripheral blood eosinophilia.

Isolation and characterization of recombinant human cathepsin E expressed in Chinese hamster ovary cells

The cDNA sequence encoding precursor forms of human cathepsin E (CE), an intracellular aspartic proteinase, was expressed in Chinese hamster ovary cells using an SV40 promotor-driven expression vector. By immunoelectron microscopic studies using an anti-human CE antibody and by Percoll density gradient fractionation, the expressed CE was found to be in two different intracellular fractions; the cytosolic compartment and the vacuolar system. The CEs in both the cytosolic and the vacuolar fractions were highly purified by a simple method involving Percoll density gradient fractionation, chromatography on concanavalin A-Sepharose, Mono Q, and TSK-GelG2000SW, and termed s-CE and v-CE, respectively. The v-CE was further separated into a major (v-CE1) and a minor (v-CE2) form by Mono Q chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting revealed that the s-CE and v-CE1 consists of two polypeptides of 90 and 84 kDa, whereas v-CE2 is composed of 84- and 82-kDa polypeptides. The NH2-terminal amino acid sequence analyses showed that the 90- and 84-kDa proteins from both s-CE and v-CE started with Ser3 and Lys30 of the sequence of human gastric CE predicted from its cDNA sequence, respectively, and that the NH2 terminus of the 82-kDa protein of v-CE2 is the Ile37. Upon acid treatment at pH 3.5 and 37 degrees C for 5 min, the 90- and 84-kDa forms are rapidly converted to the 82-kDa form, indicating that the 90-, 84- and 82-kDa proteins are the pro-CE, the intermediate form, and the mature CE, respectively. All the forms of CE are N-glycosylated with high-mannose-type oligosaccharides. The catalytic properties of s-CE and v-CE are comparable to those of natural human CE. These results suggest that the recombinant CE is initially synthesized on membrane-bound ribosomes as a N-glycosylated preproenzyme and that, after cleavage of the signal segment, the 90-kDa proenzyme is proteolytically processed to the intermediate (84 kDa) and mature (82 kDa) forms by the transport system.

[A case of advanced gastric cancer responding to an FAP (5-FU, ADM, platinum compounds) combined chemotherapy]

An experience with an advanced gastric cancer patient with metastases to bilateral breasts, uterus, abdominal lymph nodes, bilateral axillary and supraclavicular lymph nodes, and bone marrow, responded extremely well to an FAP combined chemotherapy as reported here. The patients received four courses of 5-FU (370 mg/m2/day, for five days, continuous infusion), ADM (30 mg/m2 on day 1, i.v.) and CDDP (55 mg/m2 on day 1, i.v.) every 3 weeks in our hospital. This was followed by 7 months of outpatient therapy with 5-FU (550 mg/m2 on day 1, i.v.), ADM (30 mg/m2 on day 1, i.v.) and CBDCA (330 mg/m2 on day 1, i.v.) for every 4 weeks. The complete remission of the primary and metastatic lesions, that was confirmed by the histological examinations, was obtained after 10 months since the initial treatment started. The toxicity was generally moderate, however, the alopecia was severe. The patient has been living for 6 months without any signs of the recurrence after the complete remission obtained.

Pepsinogen C gene polymorphisms associated with gastric body ulcer

This study was aimed to investigate the association of restriction fragment length polymorphisms (RFLPs) for pepsinogen genes with peptic ulcer disease. Eighty unrelated controls, 61 patients with gastric ulcer, and 57 patients with duodenal ulcer were studied. No genetic polymorphisms for pepsinogen A were detected by EcoRI digestion in Japanese subjects but a 100 base pairs insertion-deletion RFLP for the pepsinogen C gene was observed. The allele frequencies of the large (3.6 kilobase EcoRI fragment) and the small fragment (3.5 kilobase EcoRI fragment) were 80.6% and 19.4% respectively in controls, 55.4% and 44.6% in patients with gastric body ulcer, 79.4% and 20.6% in patients with gastric angular ulcer, 71.4% and 28.6% in patients with gastric antral ulcer, and 75.4% and 24.6% in patients with duodenal ulcer. The allele frequency of the small fragment was significantly higher in patients with gastric body ulcer than in controls and in patients with gastric angular or antral ulcer. The genotypes which possessed the small fragment were significantly more frequent in patients with gastric body ulcer (78.4%) than in controls (33.8%) and in patients with gastric angular or antral ulcer (37.5%). These results suggest that there is a significant association between the genetic polymorphism at the pepsinogen C gene locus and gastric body ulcer, and that the pepsinogen C RFLP is a useful marker of the genetic predisposition to this disorder. These results also indicate genetic heterogeneity of gastric ulcer disease, and suggest that the pepsinogen C RFLP may be a useful subclinical marker to explain the differences in genetic aetiologies of gastric body ulcer and gastric angular or antral ulcer.

Mutations of the chloramphenicol acetyl transferase transgene driven by the immunoglobulin promoter and intron enhancer

Transgenic mice containing the chloramphenicol acetyl transferase (CAT) gene driven by the immunoglobulin (Ig) VH promoter and the heavy chain intron enhancer were prepared to increase our understanding of the mechanism responsible for somatic mutation. The transgene showed similar tissue specificity in terms of expression as endogenous Ig genes. Hybridomas were prepared after multiple immunization of a transgenic mouse with (4-hydroxy-3-nitrophenyl)acetyl-chicken gammaglobulin, a thymus-dependent antigen. We analyzed mutations in the CAT coding region as well as in the region 5' upstream of the promoter after amplification of DNA using the PCR followed by sequencing of cloned DNA. Mutation detection enhancement gel electrophoresis was also used to detect mutations. Only a single band was observed in PCR products from the region 5' upstream of the promoter and from the enhancer, whereas in those from the CAT coding region, three out of 11 hybridomas showed multiple bands. In DNA sequences of the CAT coding region from these three hybridomas, a total of six nucleotide substitutions were observed, but none in the region 5' to the promoter. The results of DNA sequencing and the electrophoresis were in good agreement, suggesting that mutation occurred only in the CAT gene but not in the region 5' to the promoter or the enhancer. The rate of mutation in the CAT gene was estimated to be 1.6 x 10(-5) per base pair per cell division, which was a lower limit of the rate for somatic mutation reported for Ig genes. Location and distribution of mutations were similar to that of the Ig gene, suggesting that (i) mutation in the CAT gene was induced by a mechanism similar to that occurring in the Ig gene and (ii) the mutator mechanism can operate in a non-Ig gene provided it is flanked by the VH promoter and heavy chain intron enhancer.

Influence of glucose infusion on levels of phosphomonoesters and adenosine triphosphate as detected by magnetic resonance spectroscopy in a new model of core-cooling of the rat liver in situ

This preliminary study was undertaken to ascertain whether our newly developed model of the cold ischemic rat liver in situ is applicable to studies designed to assess the metabolism of nutrients. Ischemia of the whole liver of 12 Wistar rats was induced by clamping all supply and drainage vessels. The ischemic liver was perfused in situ. The duration of ischemia of the liver was 20 minutes. Saline was infused into six rats throughout the experiment (group A). An intravenous infusion of glucose at a rate of 0.75 g/h per rat was begun immediately after the induction of blood-reflow to the liver (group B, n = 6). Six rats (group C) did not undergo the procedure for induction of hepatic ischemia and received glucose at the same rate as rats in group B. Changes in hepatic levels of sugar phosphates (phosphomonoesters [PMEs]), inorganic phosphorus, and beta-positioned phosphorus in adenosine triphosphate (beta-ATP) were monitored by 31P magnetic resonance spectroscopy. Ischemia caused a significant increase in levels of PMEs and a decrease in levels of beta-ATP. The infusion of glucose caused a further increase in levels of PMEs and a further decrease in levels of beta-ATP in group B. In contrast, in group C such infusion did not induce any changes in levels of PMEs or beta-ATP. In group A, PMEs and beta-ATP returned to basal levels 5 hours after the induction of blood-reflow to the liver. The changes in levels of PMEs were similar to those in levels of inorganic phosphorus in all groups.(ABSTRACT TRUNCATED AT 250 WORDS)

A spigelian hernia in an infant

The case of a two-month old Japanese girl with a left side Spigelian hernia that developed during the course of recovery from the surgical treatment of a meningomyelocele and ventriculo-peritoneal shunting (V-P shunting) is reported on. At this time, to our knowledge, 20 cases involving infants and children have been reported on in world-wide medical literature. Of these cases, 4 cases were caused by trauma, 1 by abdominal surgery, and the others had no evident causes. Our patient had a meningomyelocele, and underwent a V-P shunting. However, a cause and effect relationship between the Spigelian hernia and the treatment of the meningomyelocele followed by V-P shunting is inconceivable. We doubt any relationship between the preceding neurosurgery and the development of the hernia. This is the first case of infantile Spigelian hernia reported on in Japan.

Isolation of a gramicidin S hyperproducing strain of Bacillus brevis by use of a fluorescence activated cell sorting system

A gramicidin S (GS) hyperproducing mutant of Bacillus brevis was isolated by using a protein-staining fluorescence dye (fluorescein isothiocyanate, FITC), and a fluorescence-activated cell sorting system (FACS). By flow cytometry (FCM) analysis after staining with FITC, higher producing cells of the wild-type had higher fluorescence signals than cells with low productivity or cells from a GS non-producing mutant. Staining with FITC did not affect the viability of cells under the conditions chosen for FCM analysis. This enabled us to recover viable cells after sorting. After wild-type cells were mutagenized with N-methyl-N'-nitro-N-nitrosoguanidine, mutants with higher fluorescence than the parental strain were obtained by cell sorting. Among them, strain 18 was chosen as a GS hyperproducer; it produced 590 micrograms GS/ml compared to 350 micrograms/ml by the wild-type strain. This method has the advantage of being able to screen large numbers of cells in a short time. Furthermore, use of the fluorescence dye technique will expand the use of FACS to the improvement of other cultures that produce metabolites that do not have a specific fluorescence or strong enough fluorescence for normal cell sorting.

Membrane region of surface IgM is not sufficient for transducing growth inhibitory signals in an immature B cell line WEHI-231

The murine B lymphoma line WEHI-231 is representative of immature B cells. Like normal immature B cells, WEHI-231 is susceptible to growth arrest following cross-linking of surface IgM (sIgM). Previously, we have shown using a WEHI-231 immunoglobulin (Ig) delta-transfectant that sIgD cross-linking failed to initiate growth arrest, in contrast to sIgM. In this report, we extend our research to investigate the structural requirement of Ig mu chain for regulating growth inhibition. Recombinant, chimeric Ig molecules delta/mu m and mu/delta m consisting of exons encoding extracellular delta and mu domains and membrane regions of different isotypes were constructed and introduced into WEHI-231 cells. A similar approach was used for sIgG2b-expressing transfectants. Our findings indicate that the mu m region is not sufficient for regulation of growth inhibition in WEHI-231 cells and suggest that additional extracellular region(s) of mu chain may be required for this response.

Detection of a polymorphism within the pepsinogen C gene with PCR: construction of a linkage map around PGC from 6p11-6p21.3

An insertion/deletion polymorphism between exons 7 and 8 of the pepsinogen C gene (PGC), previously detectable with Southern analysis, was formatted for detection with PCR. Alleles were rapidly typed by UV irradiation of ethidium bromide-stained agarose gels. Whereas Southern analysis revealed two alleles, the smaller fragments generated with PCR allowed the resolution of three alleles that were previously scored as a single allele and increased the heterozygosity of the system from 0.20 to 0.53. After a set of reference families was genotyped with the PCR-based polymorphism, a linkage map around the PGC gene on chromosome 6 was constructed. This included the HLA cluster and the highly informative D6S223 locus. PGC lies 22 cM proximal to HLA-DPB and between D6S5 and D6S4 at distances of 4.5 and 13.1 cM, respectively.

Serotype 2 reoviruses from the feces of cats with and without diarrhea

During a virus survey carried out in the period 1989-90 with 148 fecal samples collected from cats in Japan, three reovirus strains were isolated in feline cell cultures. Two strains (Nos. 114 and 140) were from 48 diarrheal fecal samples and another strain (No. 32/41) was from 100 normal fecal samples. The strains grew in feline and simian cell cultures with producing typical intracytoplasmic inclusion bodies in which virus particles were densely packed. All strains, especially Nos. 32/41 and 140 strains, showed trypsin-dependent growth in vitro. Their ultrastructural and genomic properties were characteristic of genus reovirus in the Reoviridae. All strains agglutinated erythrocytes of human type O but not of bovine. Although they were identified as serotype 2 by hemagglutination-inhibition test with the hyperimmune sera against human reovirus prototype strains, No. 114 strain was typical and the other two strains were atypical serotype 2 reoviruses. Furthermore, from the reason that Nos. 32/41 and 140 strains possessed some common properties though derived from cats in distant locations, they were considered to be reoviruses having been maintained in the cat population. Seroepizootiologic survey revealed that the prevalence of serotype 3 infection was most widespread and serotype 2 was least among three serotypes of reovirus in a cat population.