[Effect of palonidipine hydrochloride (TC-81), a new dihydropyridine derivative, on various myocardial ischemic models]

The antianginal effects of palonidipine, a novel 1,4-dihydropyridine derivative, and nifedipine on various myocardial ischemic models were compared. (1) Palonidipine at 0.5 mg/kg, p.o. significantly inhibited vasopressin-induced ST depression of ECG in Donryu rats. This activity was about 5 times more potent than that of nifedipine and was long-lasting. (2) Palonidipine at 1 mg/kg, i.d. significantly inhibited ST depression induced by isoproterenol in Wistar rats. This activity of TC-81 was more potent than that of nifedipine. (3) Palonidipine at 3 micrograms/kg, i.v. produced an increase in regional myocardial tissue blood flow in the ischemic region of chronic coronary artery occluded dogs. (4) In isolated dog coronary artery, palonidipine at a concentration of 10(-10) M or greater inhibited the amplitude of 3,4-DAP-induced cyclic contractions in a concentration-dependent manner. This activity was 10-30 times more potent than that of nifedipine. (5) An intracoronary injection of endothelin (30 pmol/kg) reduced the coronary blood flow, subepicardial tissue blood flow, and subepicardial pH in anesthetized dogs. The ST elevation of ECG over 0.1 mV also occurred in 8 of 10 cases. In all the cases, ventricular extrasystoles were noted, and 9 out of 10 animals died. Pretreatment with palonidipine (3 micrograms/kg, i.v.) inhibited endothelin-induced ischemic changes, with a potency greater than that of nifedipine. These results suggest that palonidipine may be useful for the therapy of angina-pectoris.

Cell-mediated immune-pancytopenia complicating primary Sjögren's syndrome

A 64-year-old woman with mild bilateral parotid gland swelling and bilateral lower extremity purpura was admitted for evaluation of xerostomia and pancytopenia. The patient had an increased erythrocyte sedimentation rate, pancytopenia, and positive tests for antibodies to nuclear antigen, SS-A, and SS-B. Impaired cell-mediated immunity was also present. Bone marrow aspiration showed a hypoplastic marrow with an increased percentage of lymphocytes. A positive Schirmer's test and keratoconjunctivitis were also noted. A diagnosis of primary Sjögren's syndrome was made by sialography and histological salivary gland findings. Therapy with prednisolone improved the pancytopenia. Addition of the patient's peripheral blood mononuclear cells to cultures of bone marrow mononuclear cells derived from a healthy volunteer dose dependently inhibited colony formation, including mixed hemopoietic colonies. On the other hand, addition of the patient's serum failed to inhibit colony formation by normal bone marrow mononuclear cells. These results suggested that one of the causes of pancytopenia in primary Sjögren's syndrome might be mediated by the inhibition of mononuclear cells to the hemopoietic progenitors.

Systematic assessment of bone resorption, collagen synthesis, and calcification in chick embryonic calvaria in vitro: effects of prostaglandin E2

A systematic method has been developed to assess bone resorption, matrix formation, and calcification in a single calvarial culture from 20-day-old chick embryos. The bones were prelabeled with 45Ca by an injection into the egg white before culture. In the last 2 h of incubation, the bones were further labeled with both 3H-proline and 3H-tetracycline. Bone resorption was assessed as 45Ca release into the medium. Collagen synthesis was measured by the incorporation of 3H-proline into collagenase-digestible protein (CDP). Since tetracycline has been commonly used as an in vivo marker for osteoid calcification, we assessed in vitro calcification as the uptake of 3H-tetracycline into bone. By using this method, we studied the effects of prostaglandin E2 (PGE2) and indomethacin, which inhibits biosynthesis of PGE2, on bone resorption and formation. The cultured bone synthesized approximately 300 ng of PGE2 during every 24 h of incubation, and indomethacin (10(-6) M) completely inhibited the synthesis. In indomethacin-treated cultures, % 45Ca release and the labeling of CDP were significantly reduced. These reductions were not seen when exogenous PGE2 (10(-9) M) comparable to its endogenous level was added along with the indomethacin. Furthermore, 10(-8) to 10(-5) M PGE2 increased % 45Ca release and the CDP labeling. In addition, the uptake of 3H-tetracycline into the cultured bone was also enhanced by PGE2. In devitalized calvaria, PGE2 had no effect on 3H-tetracycline uptake, suggesting that the stimulative effect on PGE2 was cell-mediated.(ABSTRACT TRUNCATED AT 250 WORDS)

Dual roles of 90-kDa heat shock protein in the function of the mineralocorticoid receptor

Association of the 90-kDa heat shock protein (HSP90) is required for the high-affinity ligand-binding of the glucocorticoid receptor (GR), but not for that of the androgen receptor [Ohara-Nemoto, Y., Nemoto, T., & Ota, M. (1991) J. Biochem. 109, 113-119]. In the present study, we investigated the ligand- and HSP90-binding characteristics of the mineralocorticoid receptor (MR), which shares to some degree the ligand-binding specificity of the GR. A truncated human MR (designated MR351) starting from Gly-351 was translated in vitro with rabbit reticulocyte lysate. Scatchard analysis revealed the presence of a single class of high-affinity binding sites for [3H]aldosterone (Kd = 0.35 +/- 0.2 nM), comparable to those of the native receptor in target tissues. Glycerol gradient centrifugation and immunoadsorption analyses showed that MR351 associated with rabbit HSP90. Exposure to 0.4 M NaCl induced the dissociation of HSP90 from MR351 and simultaneously enhanced binding of MR351 to DNA-cellulose. Moreover, when measured at 10 nM, HSP90-free MR351 showed only 9% of the [3H]aldosterone-binding found in the presence of HSP90. On the other hand, when MR351 was expressed in Escherichia coli as a protein tagged with a histidine hexamer at the N-terminus (designated H6MR351), specific binding of [3H]aldosterone was detected. The binding affinity (Kd = 338 +/- 45 nM) was, however, 1,000-fold lower than that of MR351 translated in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

cAMP-dependent phosphorylation of nuclear proteins in mouse submandibular gland following testosterone administration

The effect of androgen on protein kinase activities was studied in chromosomal proteins from female mouse submandibular gland. The protein kinase activities in the nuclei were stimulated 3 h after testosterone administration. The in vitro addition of cAMP in the nuclei resulted in the enhancement of the androgen-sensitive protein kinase activities. SDS-PAGE analysis revealed that nonhistone proteins having molecular weights of 20-30 kDa and around 43 kDa were phosphorylated after androgen treatment. The addition of cAMP stimulated phosphorylation of nonhistone proteins having molecular weights with 15-25 kDa, 30 kDa and 35 kDa and the intensity of phosphorylation of these nonhistone proteins was enhanced after androgen treatment. These results suggest that androgen-sensitive protein kinases including cAMP-dependent protein kinase were present and that phosphorylation of nonhistone proteins by these protein kinases may be involved in mediating androgen-induced gene activation.

Evidence that nitric oxide can act centrally to stimulate vasopressin release

Nitric oxide (NO) is the endothelium-derived relaxing factor, which causes relaxation of vascular smooth muscle. NO synthetase, the enzyme for the synthesis of NO from its precursor L-arginine, is also widely distributed in neurons in the brain, and it has been suggested that NO may serve as an important neuromodulator. Because NO synthetase is present in the hypothalamus in relatively high concentration, we have determined whether NO can affect the release of vasopressin in conscious, chronically prepared rats. The intracerebroventricular (i.c.v.) injection of S-nitroso-N-acetylpenicillamine (12.5 and 25 micrograms; SNAP), that spontaneously breaks down to form NO, caused transient dose-related increases in the plasma vasopressin concentration of 1 and 2 microU/ml (p < 0.01), respectively. In control experiments in which N-acetylpenicillamine (25 micrograms), the precursor for the preparation of SNAP, was injected i.c.v. there was a small, 0.4 microU/ml, increase (p < 0.01) in the plasma vasopressin level. The i.c.v. injection of L-arginine (0.5 and 1 mg), also the precursor for the biosynthesis of NO, resulted in dose-dependent increases in the plasma vasopressin concentration similar in magnitude to those caused by SNAP. When D-arginine (1 mg), which cannot serve as a substrate for NO synthetase, was injected i.c.v., there was only a slight delayed increase in the plasma vasopressin concentration. Thus, NO can act centrally to stimulate vasopressin release and may serve as a neuromodulator in the control of vasopressin release.

Transfusion-associated graft-versus-host disease in an immunocompetent patient following accidental injury

We report a case of transfusion-associated graft-vs.-host disease (TA-GVHD) in a previously healthy, 58 year old Japanese man following an accidental injury. Despite intensive treatment, the patient died 22 days after the transfusion. Although many cases of fatal TA-GVHD have been reported in immunocompetent patients, only two are known to have developed this disorder unrelated to a surgical procedure. This is the first such case to be confirmed by HLA typing. Our report suggests that TA-GVHD can occur even in a healthy, immunocompetent recipient. Thus, it seems necessary to establish guidelines for the irradiation of cellular blood products before transfusion.

Allele frequency distribution of the D1S80 (pMCT118) locus polymorphism in the Japanese population by the polymerase chain reaction

Population studies among Japanese were carried out at the D1S80 locus by the polymerase chain reaction and subsequent analysis in agarose gel electrophoresis. A total of 58 genotypes and 25 alleles ranging from 16 to 45 repeat units were observed in a population group of 121 unrelated individuals. The alleles with 18, 24 and 30 repeat units were found to be most common. Some large alleles with more than 42 repeat units were first observed in this study. Statistical tests for Hardy-Weinberg equilibrium showed that no significant deviations could be found in this Japanese population sample. The values of the mean exclusion chance and the discriminating power (DP) were calculated to be 0.76 and 0.91, respectively. The observed heterozygosity was 0.91.

Comparison of the clinical and immunogenetic features between patients with autoimmune hepatitis and patients with type C chronic active hepatitis

We clarified the clinical and immunogenetical differences between patients with autoimmune hepatitis (AI-CAH), and patients with type C chronic active hepatitis (C-CAH) and type B chronic active hepatitis (B-CAH) who were positive for autoantibodies and hyperglobulinemia. While histories of blood transfusion, intravenous drug abuse and tattoo were seen frequently in patients with type C-CAH, they were rare in patients with AI-CAH. The severe subjective symptoms including anorexia, lethargy, icterus, high fever and extrahepatic manifestations, and severe abnormality of biochemical data were seen in AI-CAH predominantly. Ongoing or past infection of HCV was seen in only 14% of patients with AI-CAH. HLA-DR4 was the most frequently associated with AI-CAH (89%) and 6 DR4-negative patients were positive for DR2. HLA-DNA typing showed that there was no significant difference in the frequency of DR4-associated Dw-alleles between the patients and controls who were positive for DR4. These findings suggest that the basic amino acid at position 13, which is present only on the DR2 and DR4 B1 molecules (Arg on DR2 and His on DR4), may contribute to the susceptibility to autoimmune hepatitis of Japanese. Thus, we conclude that AI-CAH is a genetically restricted, disease, and different from C-CAH which is a viral infectious disease.

[Molecular biological analysis of HLA class II gene in autoimmune hepatitis among Japanese]

The frequencies of HLA B54, DR4, DR53 and DQ4 were significantly higher in patients with autoimmune hepatitis than in healthy controls. HLA-DR4 was most frequently associated with autoimmune hepatitis. To define the HLA class II gene which has the susceptibility or resistance to autoimmune hepatitis, we performed HLA class II genotyping using polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) method. The frequency of DRB1*0405 was significantly higher in autoimmune hepatitis than in controls. However, there was no significant difference in the frequency of the DR4 associated Dw-allele between the patients and the controls who were DR4-positive. Six DR4-negative patients had DR2, but there was no significant difference in the frequency of the DR2-associated Dw-alleles compared with the DR2-positive controls. Comparison of the amino acid residues of DRB1 chain suggested that the basic amino acid at position 13, which is present only on the DR2 and DR4 B1 molecules (Arg on DR2 and His on DR4), contributes to the susceptibility to autoimmune hepatitis among Japanese.

[Immunological study on Alzheimer's disease using anti-beta-protein monoclonal antibodies]

Monoclonal antibodies (TB1 & TB2), which were obtained by immunization of 24 amino acids in BALB/c mice, bound specifically to the amyloid senile plaque and amyloid-angiopathic lesions of brain tissues of patients with Alzheimer's disease (AD) or with senile dementia of Alzheimer type (SDAT), and strongly reacted with the 1st part (Asp-Ala-Glu-Phe-Arg-His-Asp) of beta-protein. Western blotting and two-dimensional immunoelectrophoresis of cerebrospinal fluid (CSF) and serum revealed bands of 125 and 20 kilodaltons. The positive frequency of 125 and 20 KD bands detected by two-dimensional immunoelectrophoresis was higher in the serum of AD and SDAT patients (12 cases) than in that of normal control patients. ELISA employing various anti-amyloid precursor protein (APP) antibodies was performed using the extract of the human neuroblastoma cell line (NB39) which produces APP. In the near future, we hope to measure APP in CSF and sera from patients with Alzheimer's disease.

Prediction of the tertiary structure of parathyroid-hormone-related protein (residues 1-34) by the island model

Prediction of the tertiary structure of a 34 residue N-terminal fragment of parathyroid-hormone-related protein was carried out by the island model. This peptide is known as a major causative agent of humoral hypercalcemia of malignancy, but structural information studied by X-ray diffraction has not been reported. We adopted the secondary structure determined by NMR and packed on the basis of island model of protein folding developed by us. Predicted structure is discussed in connection with the interaction of active sites.

Effect on vasopressin release of microinjection of cholinergic agonists into the rat supraoptic nucleus

It is likely that central cholinergic pathways to the paraventricular and supraoptic nuclei participate in the control of vasopressin release. We have shown previously that this is due, in part, to activation of muscarinic, but not nicotinic, receptors in the paraventricular nucleus. There is, however, reason to believe that this cholinergic effect in the supraoptic nucleus may be the result of activation of nicotinic receptors. To test this possibility, we have studied in conscious unrestrained rats the effect of microinjection of muscarinic and nicotinic agonists into the supraoptic nucleus on vasopressin release, mean arterial blood pressure, and heart rate. Under ether anesthesia, a stainless steel guide cannula was placed in the supraoptic nucleus 5-7 days before the experiment, and femoral, arterial, and venous catheters were implanted 1 day before the experiment. Microinjection of nicotine into the supraoptic nucleus at doses of 1 and 10 micrograms resulted in transient increases in the plasma vasopressin concentration that were 7-fold and 11-fold greater, respectively, than control values at 3 min. There were also small transient increases in mean arterial blood pressure, but heart rate was unchanged. The microinjection of 2 and 20 ng of oxotremorine, a muscarinic agonist, into the supraoptic nucleus had no effect on the plasma vasopressin concentration, mean arterial blood pressure, or heart rate. These doses of oxotremorine were previously shown to have potent stimulatory effects on vasopressin release when microinjected into the paraventricular nucleus. These findings suggest that the central cholinergic stimulation of vasopressin release is due, in part, to activation of muscarinic receptors in the paraventricular nucleus and nicotinic receptors in the supraoptic nucleus.

Central carbachol stimulates vasopressin release into interstitial fluid adjacent to the paraventricular nucleus

We have used an in vivo double microdialysis probe technique in conscious rats to determine whether the application of carbachol to one paraventricular nucleus (PVN) can result in increased local release of vasopressin from that PVN. Experiments were carried out 24 h after placement of microdialysis probes lateral to each PVN. When both probes were perfused initially with 0.9% NaCl, vasopressin was detected in the outflow (dialysate) from both probes. When carbachol (100 micrograms/ml) was included in the perfusate of one probe for the first 10 min of a 30-min collection period, while the other probe continued to be perfused with saline alone, there was a seven-fold increase in the concentration of vasopressin in the dialysate from the carbachol-perfused probe; the vasopressin concentration in the dialysate from the contralateral probe increased only slightly. The plasma vasopressin concentration was also elevated. When one of the paired probes was perfused with carbachol (100 micrograms/ml) for 30 min, there were similar increases in the concentration of vasopressin in the dialysate from both probes and a sustained increase in the plasma vasopressin concentration. Thus, vasopressin is released into the interstitial fluid adjacent to the PVN under basal conditions, and this release can be substantially increased when vasopressin secretion to the periphery is stimulated.

HLA class II molecules and autoimmune hepatitis susceptibility in Japanese patients

To investigate the association between autoimmune hepatitis and HLA alleles in Japanese patients, serological typing and class II genotyping were performed using the polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) method. Serological typing showed that HLA-B54, -DR4, -DR53, and -DQ4 were significantly more frequent in patients with autoimmune hepatitis than in controls. HLA-DR4 was most frequently associated with autoimmune hepatitis (88.7%). In PCR-RFLP typing, the frequency of DRB1*0405 was significantly higher in autoimmune hepatitis than in controls. However, there was no significant difference in the frequency of Dw between the patients and the controls who were DR4-positive. The significant increase observed in DQA1*0301 and DQB1*0401 was explained by a linkage disequilibrium with DR4. Six DR4-negative patients had DR2, but there was no significant difference in the frequency of the DR2-associated Dw-alleles compared with the DR2-positive controls. No DPB1 allele was significantly associated with autoimmune hepatitis. These findings suggest that the basic amino acid at position 13, which is present only on the DR2 and DR4 B1 molecules (Arg on DR2 and His on DR4), contributes to the susceptibility to autoimmune hepatitis among the Japanese.

Association of the 90-kDa heat shock protein does not affect the ligand-binding ability of androgen receptor

An N-terminal truncated androgen receptor with putative DNA- and ligand-binding domains (AR438) and that with a ligand-binding domain (AR612) were expressed under control of the T7 promoter in E. coli or translated in vitro with rabbit reticulocyte lysate, and their ligand-binding properties and the interaction with HSP90 were investigated. Bacterially expressed AR438 and AR612 bound a synthetic androgen, [3H]R1881, with apparent dissociation constants of 2.6 +/- 0.2 and 3.1 +/- 0.7 nM, respectively, values which are comparable to those of androgen receptor in target tissues. The recombinant androgen receptors sedimented at the 4-5 S region irrespective of the presence of 10 mM tungstate, indicating that the receptor exists free from HtpG, which is the bacterial homolog of eukaryotic HSP90. The apparent dissociation constant of truncated androgen receptors translated in vitro was 0.1 nM for AR438 and 0.2 nM for AR612. Sedimentation coefficients of in vitro translated molecules were converted from 7-8 S in the presence of tungstate to 3 S in the absence of tungstate. Both AR438 and AR612 translated in vitro were retained by anti-rat HSP90 antibody-protein A Sepharose. Exposure to 0.3 M NaCl in the presence of ligand caused dissociation of AR438 and AR612 from HSP90, and concomitantly, the DNA-cellulose binding ability of AR438 was enhanced. Thus, we conclude that the androgen receptor associates with HSP90 through the ligand-binding domain and that this association prevents the interaction of the androgen receptor with DNA. However, HSP90 seems to have little effect on the ligand-binding characteristics of the androgen receptor.

[A case report of well differentiated fetal adenocarcinoma]

A 32-year-old female, who was admitted with complaints of cough and an abnormal shadow in the left lower lobe, was diagnosed as adenocarcinoma of the lung by TBLB. She underwent left lower lobectomy and lymph node dissection. Histopathological findings showed well differentiated fetal adenocarcinoma (WDFA). Well differentiated fetal adenocarcinomas are considered to have a histogenesis similar to that of pulmonary blastoma and may be a tumor with one-sided development of pulmonary blastoma showing only an epithelial component.

N-methylation of dopamine-derived 6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline, (R)-salsolinol, in rat brains: in vivo microdialysis study

N-Methylation of (R)-1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline [(R)-salsolinol] derived from dopamine was proved by in vivo microdialysis study in the rat brain. The striatum was perfused with (R)-salsolinol and N-methylated compound was identified in the dialysate using HPLC and electrochemical detection with multichanneled electrodes. N-Methylation of (R)-salsolinol was confirmed in three other regions of the brain, the substantia nigra, hypothalamus, and hippocampus. In the substantia nigra, the amount of N-methylated (R)-salsolinol was significantly larger than in the other three regions. These results indicate that around dopaminergic neurons, particularly in the substantia nigra, (R)-salsolinol was methylated into N-methyl-(R)-salsolinol, which has a chemical structure similar to that of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, the selective dopaminergic neurotoxin. N-Methylation of tetrahydroisoquinolines and beta-carbolines have already been proven to increase their toxicity to dopaminergic neurons and N-methylation might be an essential step for these alkaloids to increase their toxicity. On the other hand, after perfusion of (R)-salsolinol, release of dopamine and 5-hydroxytryptamine was observed and inhibition of monoamine oxidase was indicated. (R)-Salsolinol and its derivatives may be candidates for being dopaminergic neurotoxins.

A possible association between basic amino acids of position 13 of DRB1 chains and autoimmune hepatitis

Fifty-one patients with autoimmune hepatitis have been studied for HLA association by conventional serology and also by modified polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) genotyping. HLA-DR4 was significantly associated with autoimmune hepatitis (46 of 51 patients, 90.2%). DNA typing of the DRB1 gene for 43 DR4-positive patients by using the PCR-RFLP technique revealed that of 43 patients, 33 had DRB1*0405 (Dw15), five had DRB1*0406 (DwKT2), four had DRB1*0403 (Dw13a), two had DRB1*0401 (Dw4), two of 43 had DRB1*0407 (Dw13b) and one had DRB1*0408 (Dw14b). Thus, there was no significant difference in Dw frequencies between DR4-positive patients and DR4-positive healthy subjects. These findings suggest that the DR4-specific sequence (Val 11 and His 13 at amino acid positions 11 and 13, respectively), but not particular Dw-associated DR4 sequence, in the first domain of the DRB1 chain contributes to susceptibility to autoimmune hepatitis among Japanese. Interestingly, all five of the DR4-negative patients had the DR2 specificity (DRB1*1502 or 1601). Taken together, these results imply that the basic amino acids at position 13, which is present only on the DR2 and DR4 B1 molecules (Arg on DR2 and His on DR4), are most important for determining the predisposition to autoimmune hepatitis.

[Phase II study of 254-S (cis-diammine glycolato platinum) for gynecological cancer]

A phase II study of 254-S was conducted in 134 patients with gynecological malignancies by the gynecology section of the 254-S cooperative study group. The drug was administered at least twice at a dose of 100 mg/m2 by intravenous infusion at 4 week intervals. Forty-two of the 102 evaluable patients responded, including 8 CRs and 34 PRs, with a response rate of 41.2%. The response rate was 37.7% for ovarian cancer and 46.3% for cervical cancer. The response rate of 46.3% for cervical cancer was the highest reported for any single anticancer agent available in Japan. The major side effect was hematotoxicity, in particular thrombocytopenia and leukopenia, while nephrotoxicity was rarely observed. These results suggest that 254-S is an active cisplatin analogue with reduced nephrotoxicity and is a very promising anticancer agent for the treatment of ovarian and cervical cancer.

Effects of androgen on phosphorylation of chromosomal proteins in mouse submandibular gland

The effect of androgen on intranuclear distribution of androgen receptor binding sites was studied. The level of the androgen receptor complex in dinucleosomes increased 1 h after androgen treatment and those in the mono- and trinucleosomes increased 3 h after androgen treatment. Investigation by 32P incorporation into the nuclei and active chromatin showed that androgen resulted in an increase in the rate of phosphorylation at 3 h and reduced to the control level at 6 h. These data suggest that association of androgen receptor with the acceptor sites and activities of protein kinase in active chromatin are simultaneously stimulated for activating the transcription by androgen.

HLA-DRB1 genotyping by modified PCR-RFLP method combined with group-specific primers

We previously introduced HLA-DQA1, -DPB1 and DQB1 genotyping with the modified PCR-RFLP method using some informative restriction enzymes which have either a single cleavage site or alternatively no cleavage site in the amplified DNA region, depending on the HLA alleles, making reading of RFLP band patterns much easier. In this study, 43 HLA-DRB1 alleles, excluding DRB1*1103 and *1104 for which no restriction enzymes are available to distinguish each from the other, could be defined by this modified PCR-RFLP method combined with 7 pairs of group-specific primers. It is impossible to distinguish DRB1*0701 and DRB1*0702 as they are identical for the second exon of DRB1. For DR1-DRB1, DR2-DRB1, DR4-DRB1, DR7-DR1, DR9-DRB1, DRw10-DRB1 or DRw52 associated antigens (DR3, w11, w12, w13, w14, and DRw8)-DRB1 gene amplification, the second exon of the DRB1 gene was selectively amplified using each group-specific primer from genomic DNAs of 70 HLA-homozygous B-cell lines and healthy Japanese by PCR. Amplified DNAs were digested with restriction endonucleases and then subjected to electrophoresis assaying simply for cutting, or no cutting, of the DNA, although some alleles can be distinguished only after examination of RFLP band patterns generated and in some cases using double digestion technique with two restriction enzymes. This modified PCR-RFLP method can be successfully applied to all possible DRB1 heterozygotes, despite the fact that 15 pairs of heterozygotes among them cannot be distinguished theoretically by the PCR-SSO method, because the PCR-RFLP method can tell whether two polymorphic sites are linked to each other (cis position) or located on a different chromosome (trans position) by checking the length of RFLP bands generated with double digestion. Thus, the PCR-RFLP method is technically simple, practical and inexpensive for determination of the HLA-DRB1 alleles for routine HLA typing work.