TAP-deficient human iPS cell-derived myeloid cell lines as unlimited cell source for dendritic cell-like antigen-presenting cells.

We previously reported a method to generate dendritic cell (DC)-like antigen-presenting cells (APC) from human induced pluripotent stem (iPS) cells. However, the method is relatively complicated and laborious. In the current study, we attempted to establish a method through which we could obtain a large number of functional APC with a simple procedure. We transduced iPS cell-derived CD11b(+) myeloid cells with genes associated with proliferative or anti-senescence effects, enabling the cells to propagate for more than 4 months in a macrophage colony-stimulating factor (M-CSF)-dependent manner while retaining their capacity to differentiate into functional APC. We named these iPS cell-derived proliferating myeloid cells 'iPS-ML', and the iPS-ML-derived APC 'ML-DC'. In addition, we generated TAP2-deficient iPS cell clones by zinc finger nuclease-aided targeted gene disruption. TAP2-deficient iPS cells and iPS-ML avoided recognition by pre-activated allo-reactive CD8(+) T cells. TAP2-deficient ML-DC expressing exogenously introduced HLA-A2 genes stimulated HLA-A2-restricted MART-1-specific CD8(+) T cells obtained from HLA-A2-positive allogeneic donors, resulting in generation of MART-1-specific cytotoxic T lymphocyte (CTL) lines. TAP-deficient iPS-ML introduced with various HLA class I genes may serve as an unlimited source of APC for vaccination therapy. If administered into allogeneic patients, ML-DC with appropriate genetic modifications may survive long enough to stimulate antigen-specific CTL and, after that, be completely eliminated. Based on the present study, we propose an APC-producing system that is simple, safe and applicable to all patients irrespective of their HLA types.

Generation of dendritic cells and macrophages from human induced pluripotent stem cells aiming at cell therapy.

This report describes generation of dendritic cells (DCs) and macrophages from human induced pluripotent stem (iPS) cells. iPS cell-derived DC (iPS-DC) exhibited the morphology of typical DC and function of T-cell stimulation and antigen presentation. iPS-DC loaded with cytomegalovirus (CMV) peptide induced vigorous expansion of CMV-specific autologous CD8+ T cells. Macrophages (iPS-MP) with activity of zymosan phagocytosis and C5a-induced chemotaxis were also generated from iPS cells. Genetically modified iPS-MPs were generated by the introduction of expression vectors into undifferentiated iPS cells, isolation of transfectant iPS cell clone and subsequent differentiation. By this procedure, we generated iPS-MP expressing a membrane-bound form of single chain antibody (scFv) specific to amyloid ß (Aß), the causal protein of Alzheimer's disease. The scFv-transfectant iPS-MP exhibited efficient Aß-specific phagocytosis activity. iPS-MP expressing CD20-specific scFv engulfed and killed BALL-1 B-cell leukemia cells. Anti-BALL-1 effect of iPS-MP in vivo was demonstrated in a xeno-transplantation model using severe combined immunodeficient mice. In addition, we established a xeno-free culture protocol to generate iPS-DC and iPS-MP. Collectively, we demonstrated the possibility of application of iPS-DC and macrophages to cell therapy.

Identification of HLA-A2-restricted CTL epitopes of a novel tumour-associated antigen, KIF20A, overexpressed in pancreatic cancer.

BACKGROUND: Identification of tumour-associated antigens (TAAs) that induce cytotoxic T lymphocytes (CTLs) specific to cancer cells is critical for the development of anticancer immunotherapy. In this study, we aimed at identifying a novel TAA of pancreatic cancer for immunotherapy. METHODS: On the basis of the genome-wide cDNA microarray analysis, we focused on KIF20A (also known as RAB6KIFL/MKlp2) as a candidate TAA in pancreatic cancer cells. The HLA-A2 (A*02:01)-restricted CTL epitopes of KIF20A were identified using HLA-A2 transgenic mice (Tgm) and the peptides were examined to check whether they could generate human CTLs exhibiting cytotoxic responses against KIF20A(+), HLA-A2(+) tumour cells in vitro. RESULTS: KIF20A was overexpressed in pancreatic cancer and in some other malignancies, but not in their non-cancerous counterparts and many normal adult tissues. We found that KIF20A-2 (p12-20, LLSDDDVVV), KIF20A-8 (p809-817, CIAEQYHTV), and KIF20A-28 (p284-293, AQPDTAPLPV) peptides could induce HLA-A2-restricted CTLs in HLA-A2 Tgm without causing autoimmunity. Peptide-reactive human CTLs were generated from peripheral blood mononuclear cells of HLA-A2(+) healthy donors by in vitro stimulation with the three peptides, and those CTLs successfully exhibited cytotoxic responses to cancer cells expressing both KIF20A and HLA-A2. CONCLUSION: KIF20A is a novel promising candidate for anticancer immunotherapeutic target for pancreatic cancers.

Identification of SARS-COV spike protein-derived and HLA-A2-restricted human CTL epitopes by using a new muramyl dipeptidederivative adjuvant.

Severe acute respiratory syndrome (SARS) spread during the winter of 2003, and attempts have been made to develop vaccines against SARS corona virus (SARS-CoV). The present study provides a strategy to rapidly identify SARS-CoV-derived antigenic peptides recognized by HLA-A2-restricted cytotoxic T lymphocytes (CTLs). Forty-three candidate peptides having HLA-A2-binding motifs were selected in silico and HLA-A2/Db chimeric MHC class I-transgenic mice were immunized with these peptides and a new derivative of muramyl dipeptide that can induce upregulation of HLA-DR, CD80, CD86, and CD40 in human CD14+ antigen presenting cells, was administered as an adjuvant. Six HLAA2-restricted mouse CTL epitopes were identified, including two new epitopes which have never been reported before. One of the novel peptides was naturally processed and successfully induced HLAA2-restricted specific CTLs in both HLA transgenic mice and healthy donors. The method was useful, convenient and efficient for rapid identification of CTL epitopes derived from SARS-CoV proteins and will be possibly applicable for other pathogens to develop a peptide-based vaccine.

Massive cell death of immature hematopoietic cells and neurons in Bcl-x-deficient mice.

bcl-x is a member of the bcl-2 gene family, which may regulate programmed cell death. Mice were generated that lacked Bcl-x. The Bcl-x-deficient mice died around embryonic day 13. Extensive apoptotic cell death was evident in postmitotic immature neurons of the developing brain, spinal cord, and dorsal root ganglia. Hematopoietic cells in the liver were also apoptotic. Analyses of bcl-x double-knockout chimeric mice showed that the maturation of Bcl-x-deficient lymphocytes was diminished. The life-span of immature lymphocytes, but not mature lymphocytes, was shortened. Thus, Bcl-x functions to support the viability of immature cells during the development of the nervous and hematopoietic systems.

Immunocytochemical analyses and targeted gene disruption of GTPBP1.

We previously identified a gene encoding a putative GTPase, GTPBP1, which is structurally related to elongation factor 1alpha, a key component of protein biosynthesis machinery. The primary structure of GTPBP1 is highly conserved between human and mouse (97% identical at the amino acid level). Expression of this gene is enhanced by gamma interferon in a monocytic cell line, THP-1. Although counterparts of this molecule in Caenorhabditis elegans and Ascaris suum have also been identified, the function of this molecule remains to be clarified. In the present study, our immunohistochemical analyses on mouse tissues revealed that GTPBP1 is expressed in some neurons and smooth muscle cells of various organs as well as macrophages. Immunofluorescence analyses revealed that GTPBP1 is localized exclusively in cytoplasm and shows a diffuse granular network forming a gradient from the nucleus to the periphery of the cells in smooth muscle cell lines and macrophages. To investigate the physiological role of GTPBP1, we used targeted gene disruption in embryonic stem cells to generate GTPBP1-deficient mice. The mutant mice were born at the expected Mendelian frequency, developed normally, and were fertile. No manifest anatomical or behavioral abnormality was observed in the mutant mice. Functions of macrophages, including chemotaxis, phagocytosis, and nitric oxide production, in mutant mice were equivalent to those seen in wild-type mice. No significant difference was observed in the immune response to protein antigen between mutant mice and wild-type mice, suggesting normal function of antigen-presenting cells of the mutant mice. The absence of an eminent phenotype in GTPBP1-deficient mice may be due to functional compensation by GTPBP2, a molecule we recently identified which is similar to GTPBP1 in structure and tissue distribution.

Humoral immune response directed against LEDGF in patients with VKH.

Vogt-Koyanagi-Harada disease is an autoimmune systemic disorder. In Vogt-Koyanagi-Harada disease, inflammatory disorders occur in multiple organs containing melanocytes, including uvea (resulting in acute bilateral panuveitis), skin (resulting in vitiligo and alopecia), central nervous system (resulting in meningitis) and inner ears (resulting in hearing loss and tinnitus). These inflammatory aspects are attributed to the destruction of melanocytes through immunological mechanisms. Studies have been carried out to elucidate the exact etiology and target autoantigen in Vogt-Koyanagi-Harada disease, but much remains to be investigated. Identification of target autoantigen is important to understand the etiology of autoimmune diseases, and for development of antigen-specific immuno-modulation therapy. To identify the target autoantigens in Vogt-Koyanagi-Harada disease, we made use of an immunoscreening of a bovine uveal cDNA expression library with serum samples obtained from patients with Vogt-Koyanagi-Harada disease. We identified an immunoreactive cDNA clone that encodes bovine lens epithelium derived growth factor. mRNA of human lens epithelium derived growth factor was determined by reverse transcription-polymerase chain reaction and it was expressed in human uvea, retina and melanocytes. Immunoglobulin G (IgG) autoantibodies were quantitated in an enzyme-linked immunosorbent assay, using recombinant human lens epithelium derived growth factor. The prevalence of IgG anti-lens epithelium derived growth factor autoantibodies in patients with Vogt-Koyanagi-Harada disease was significantly higher than that in healthy controls (66.7% versus 21.6%, P<0.001). On the other hand, the prevalence of the autoantibody in patients with panuveitis of other etiology, Behçet's disease and sarcoidosis, was almost same as that in healthy controls. These results suggest that the humoral immune response agonist lens epithelium derived growth factor is not a mere secondary phenomena caused by uveal tissue damage.

Immuno-suppressive peptides for a human T cell clone autoreactive to a unique acetylcholine receptor alpha subunit peptide presented by the disease-susceptible HLA-DQ6 in infant-onset myasthenia gravis.

Infant-onset myasthenia gravis, an autoimmune disease specific to Asians predominantly affects neuromuscular junctions in ocular muscles. An AChR alpha peptide (p71-91) specific autoreactive CD4+ alpha beta T cell clone was established by stimulating PBMC from a patient heterozygous for two disease-susceptible HLA-DR9-DQ9 and DR13-DQ6 haplotypes with a mixture of overlapping peptides covering AChR alpha. The T cell clone recognized the AChR alpha peptide in the context of the HLA-DQ6 molecule and produced a large amount of IFN-gamma and a trace amount of IL-4. A part (p75-83) of the core epitope of the autoantigenic peptide (p75-87) is encoded for by an exon P3A of the AChR alpha gene which can be alternatively spliced. The T cell clone responded to the recombinant AChR alpha protein with a P3A exon product, but not without a P3A exon product. We investigated responses of the T cell clone to 114 analogue peptides carrying single residue substitutions of the core AChR alpha peptide. The majority of analogues substituted at residues Phe-77, Leu-80 and Asn-82 stimulated proliferation of the T cell clone. Conversely, the majority of analogue peptides substituted at either Gln-81 or Glu-83 did not stimulate proliferative responses, and all exhibited strong or intermediate inhibitory effects on proliferative responses of the T cell clone to the wild type peptide, possibly by TCR antagonism. Thus, an HLA class II allele specific to Asians may directly control susceptibility to the Asian-specific type of myasthenia gravis. Analogues of the auto-antigenic AChR alpha peptide may prove effective for new immunosuppressive therapy.

The CLIP-substituted invariant chain efficiently targets an antigenic peptide to HLA class II pathway in L cells.

The presentation of antigenic peptides by major histocompatibility complex (MHC) class II to CD4+ T cells is crucial to initiate immune responses. We developed a new system for delivery of an antigenic peptide to the MHC class II pathway, using the invariant chain (Ii). We designed a mutated human p33-form Ii, CLIP-substituted Ii, in which streptococcal M12p55-68 (RDLEQAYNELSGEA) was substituted for CLIP (class II associated invariant chain peptide). We examined the peptide presenting function of this construct, in comparison with the previously reported C-terminal fused Ii, in which a cathepsin cleavage site and M12p54-68 was ligated to the C-terminus of Ii. Mouse L cell transfectants expressing either of these two mutated Ii along with HLA-DR4 could process and present M12p55-68 to the peptide specific and DR4-restricted CD4+ T cell clone. CLIP-substituted Ii was much more efficient in antigen presentation than was the C-terminal fused Ii. Similar to the wild-type Ii, the CLIP-substituted Ii was associated intracellularly with DR4 molecules. These results indicate that the peptide substituted for CLIP of Ii p33 bound to the groove of DR molecules in the same manner as CLIP and it was preferentially presented to the CD4+ T cell clone in the absence of HLA-DM molecules. This system may prove useful for immunotherapy with DNA vaccines or for construction of an antigen presenting cell library with diverse peptides.

Factors related to the relapse of bronchiolitis obliterans organizing pneumonia.

STUDY OBJECTIVE: The purpose of this study is to determine factors, including laboratory data, related to the relapse of bronchiolitis obliterans organizing pneumonia (BOOP). DESIGN: Retrospective study. SETTING AND PATIENTS: The medical files of Fukuoka University Hospital and Nishi Fukuoka Hospital patients from 1984 to 1996 were reviewed, and 18 cases of BOOP that had been diagnosed using transbronchial or open lung biopsy were selected for evaluation. MEASUREMENTS: The 18 cases were put into two groups composed of 7 patients who relapsed and 11 who did not relapse. Their clinical symptoms and laboratory data at first admission, including hemograms, blood chemistry tests, and pulmonary function tests were compared. Patients with or without associated diseases, such as collagen vascular diseases, were compared using the same parameters in order to examine the relationship between the associated diseases and BOOP relapse. RESULTS: The serum levels of total protein and albumin in patients who relapsed were significantly lower than in patients who did not relapse, respectively: 5.8 (range, 4.4 to 6.2) vs 6.3 (range, 4.5 to 6.8) g/dL, p < 0.05; and 2.9 (range, 2.5 to 3.4) vs 3.7 (range, 2.8 to 4.3) g/dL, p < 0.01. Levels of serum albumin in BOOP patients with associated diseases, however, were significantly lower than in those without associated diseases, respectively: 2.95 (range, 2.5 to 3.9) vs 3.65 (range, 2.8 to 4.3) mg/dL, p < 0.05. The fall in serum albumin levels in patients who relapsed, therefore, was probably due to associated diseases. The fact that 5 of 8 patients with associated diseases relapsed but only 2 of 10 without associated diseases relapsed suggests that a relationship exists between associated diseases and the prognosis of BOOP, although this finding was not statistically significant because of the small number of cases and the heterogeneity of the associated diseases. The most striking observation was that PaO2 levels in patients who relapsed were significantly lower than in those who did not, respectively: 55.4 (range, 39.9 to 73.2) vs 78.0 (range, 48.4 to 89.4) mm Hg, p < 0.05. However, PaO2 levels were not statistically different between patients with and without associated diseases, respectively: 66.0 (range, 45.4 to 78.8) vs 71.4 (range, 39.9 to 89.4) mm Hg. CONCLUSIONS: The severity of hypoxemia at first medical examination may be an important determinant for the subsequent BOOP relapse.

Neutrophils become refractory to phorbol myristate acetate when treated with Ca2+-ionophore and Ca2+.

Human neutrophils deprived of divalent cations by treatment with ionophore A23187 in the presence of ethylene glycol bis(beta-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) showed superoxide release when they were preincubated with calcium and then treated with the ionophore. The release was not observed when the ionophore was added first and then calcium was added more than 5 min later. The absence of the release in this case can be ascribed to a refractoriness of the cells to stimuli, because the cells did not release superoxide on stimulation with phorbol myristate acetate (PMA). The cells pretreated with either calcium or the ionophore alone did release superoxide on addition of PMA. The refractoriness of the cells to PMA depended on the concentrations of calcium and the ionophore and on the time interval between the two treatments. Calcium could be replaced with Cd2+ but not with Mg2+, Ba2+, or Sr2+. The release of granular enzymes was observed when the depleted cells were pretreated with the ionophore and then with calcium. These observations indicate that calcium has dual effects on the superoxide release of neutrophils, i.e., it stimulates the cells and makes them refractory to stimuli, depending on the time interval after the addition of the ionophore, and it also regulates the enzyme release by a different mechanism.

Thickness of the basement membrane of bronchial epithelial cells in lung diseases as determined by transbronchial biopsy.

The thickness of the basement membranes of bronchial epithelial cells varies under various pathological conditions. It has been reported that this membrane is thickened in patients with bronchial asthma. By light microscopy, this parameter was measured in biopsy specimens of bronchial mucosa obtained by fibre-optic bronchoscopy. These specimens were obtained from 171 patients who had undergone bronchial biopsy between 1984 and 1994. It was demonstrated that the thickness of the basement membrane of bronchial epithelial cells was weakly correlated with the patient's age, when thickness was examined in patients with lung cancer (r = 0.242, P = 0.0268). The basement membranes in patients with bronchial asthma (8.193 +/- 1.362 mu, mean +/- SEM) were significantly thicker than those without bronchial asthma (5.145 +/- 0.233 mu) (P = 0.0180, Mann-Whitney's U-test). In addition, it is noteworthy that the basement membranes in patients with diabetes mellitus (7.217 +/- 0.753 mu) were also significantly thicker than those without diabetes mellitus (4.968 +/- 0.235 mu) (P = 0.0038, Mann-Whitney's U-test). The background or underlying pathophysiology in such patients should be studied further, with attention directed towards the thickness of the bronchial basement membrane in bronchial biopsy specimens.

Long-term continuous intravenous infusion of prostacyclin for severe primary pulmonary hypertension.

A patient suffering from severe symptomatic primary pulmonary hypertension (PPH) underwent long-term intravenous prostacyclin therapy; the first time for such treatment in Japan. A 26-year-old male had experienced gradually progressive dyspnea for about one year. Despite conventional therapy he suffered repeated syncopal attacks. However, after receiving a permanent central venous access device and a portable infusion pump, he recovered fully and was discharged. This remedy seems to be promising for PPH as has already been proven in Europe and North Americas, although in Japan it is not as yet commercially available and some problems still need to be resolved.

[Pathogenic bacteria isolated from the sputum of the patients with pulmonary emphysema].

Isolated pathogenic bacteria from sputum of the patients with pulmonary emphysema who were admitted in our hospital from 1984 to 1994 were examined to elucidate the relationship between isolated bacteria from sputum and pulmonary functions including vital capacity (VC), forced expiratory volume (FEV1.0), PaO2 and PaCO2. VC of the patients from whom MSSA (methicillin-sensitive Staphylococcus aureus) or Enterococcus faecalis (E. faecalis) were isolated was significantly lower than that of the patients from whom Streptococcus pneumoniae (S. pneumoniae), Branhamella catarrhalis (B. catarrhalis) or Haemophilus influenza (H. influenza) were isolated. FEV1.0 had a similar tendency as VC in terms of isolated organisms from the patients with emphysema. Similarly, PO2 of the patients from whom MSSA or E. cloacae were isolated was significantly lower than that of the patients from whom S. pneumoniae, B. catarrhalis or H. influenzae were isolated, and PCO2 of the patients from whom S. pneumoniae, B. catarrhalis or H. influenza were isolated. There was also impaired respiratory function in the patients from whom MSSA, Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa), Xanthomonas maltophilia (X. maltophilia) or Enterobacter cloacae (E. cloacae) were isolated, compared with those in the patients from whom S. pneumonia, B. catarrhalis or H. influenzae were isolated. These results suggest that isolated pathogenic bacteria are shifted from S. pneumoniae, B. catarrhalis or H. influenza to MSSA, E. coli, P. aeruginosa, X. maltophilia or E. cloacae in the course of impairment of respiratory function in pulmonary emphysema. The treatment and prophylaxis for acute exacerbation in pulmonary emphysema should be based on these results.

[Clinical efficacy of imipenem/cilastatin sodium for respiratory infections in patients with lung cancer].

Imipenem/cilastatin sodium (IPM/CS) was administered to 102 patients with respiratory tract infections and lung cancer. Patients with other serious diseases were excluded and a total of 73 patients were enrolled. They were divided into 12 patients who underwent surgery (operated group) and 61 who did not (non-operated group); the latter group included 28 patients treated with anticancer agents or radiation therapy (treated group) and 33 untreated patients (untreated group). IPM/CS was effective in 75% of the patients, both with and without surgery. The drug was effective in 81% of the treated group, although many of the patients had Stage III or more advanced cancer, as well as bronchial occlusion. IPM/CS was also effective in 69% of the untreated group, although many of the patients have serious infections and a PS (Performance Status) of 3 or greater. Thus, IPM/CS treatment achieved good results. Bacteriological studies showed that 3 out of 4 strains in the operated group and 16 out of 18 in the non-operated group were eliminated. Safety was evaluated in all patients. Two patients (2%) experienced side effects and two others (2%) showed abnormal clinical findings, but the symptoms were mild and resolved after discontinuation or completion of therapy. In conclusion, IPM/CS was very effective for treating respiratory infections in patients with lung cancer.

Identification of human and mouse GP-1, a putative member of a novel G-protein family.

To identify genes induced in monocytes by interferon-gamma, we carried out PCR-based cDNA subtraction and subsequent differential display on mRNA isolated from a human monocytic leukemia cell line, THP-1. We detected a novel gene encoding a protein bearing GTP-binding motifs, the characteristics of GTP-binding proteins (G-proteins). We also identified the mouse homologue of this gene and designated the gene GP-1. The amino acid sequence of GP-1 deduced from the nucleotide sequence is highly conserved in human and mouse (97% identical over the entire protein), suggesting a fundamental physiological role for this molecule. As amino acid sequences of GTP-binding motifs of human and mouse GP-1 are practically identical to those of recently identified putative G-proteins of nematode, AGP-1 and CGP-1, these proteins are likely to be members of the same, novel G-protein family. GP-1 mRNA was readily detected in mouse brain, thymus, lung, and kidney, while GP-1 mRNA is rarely expressed in liver.

Four cases of bronchiolitis obliterans organizing pneumonia associated with thyroid disease.

We present 4 cases of bronchiolitis obliterans organizing pneumonia (BOOP) associated with thyroid diseases. Case 1 had previously undergone surgery for thyroid cancer, and had a secondary hypothyroidism at the onset of BOOP. Case 2 developed Basedow's disease 3 months after the onset of BOOP and BOOP relapsed 21 months after the onset of Basedow's disease. Case 3 developed subacute thyroiditis 33 months after the onset of BOOP, and has had no relapse of BOOP for 7 years. Case 4 had hypothyroidism at the time of diagnosis of BOOP, and her BOOP relapsed 3 months after the initial onset of BOOP. Two of these 4 cases of BOOP with thyroid diseases relapsed, and thyroid dysfunction could modify the pathophysiology of BOOP.

Mouse and human GTPBP2, newly identified members of the GP-1 family of GTPase.

We earlier identified the GTPBP1 gene which encodes a putative GTPase structurally related to peptidyl elongation factors. This finding was the result of a search for genes, the expression of which is induced by interferon-gamma in a macrophage cell line, THP-1. In the current study, we probed the expressed sequence tag database with the deduced amino acid sequence of GTPBP1 to search for partial cDNA clones homologous to GTPBP1. We used one of the partial cDNA clones to screen a mouse brain cDNA library and identified a novel gene, mouse GTPBP2, encoding a protein consisting of 582 amino acids and carrying GTP-binding motifs. The deduced amino acid sequence of mouse GTPBP2 revealed 44.2% similarity to mouse GTPBP1. We also cloned a human homologue of this gene from a cDNA library of the human T cell line, Jurkat. GTPBP2 protein was found highly conserved between human and mouse (over 99% identical), thereby suggesting a fundamental role of this molecule across species. On Northern blot analysis of various mouse tissues, GTPBP2 mRNA was detected in brain, thymus, kidney and skeletal muscle, but was scarce in liver. Level of expression of GTPBP2 mRNA was enhanced by interferon-gamma in THP-1 cells, HeLa cells, and thioglycollate-elicited mouse peritoneal macrophages. In addition, we determined the chromosomal localization of GTPBP1 and GTPBP2 genes in human and mouse. The GTPBP1 gene was mapped to mouse chromosome 15, region E3, and human chromosome 22q12-13.1, while the GTPBP2 gene is located in mouse chromosome 17, region C-D, and human chromosome 6p21-12.

Allele-specific expression of the cytoplasmic exon of HLA-DQB1 gene.

The beta chain of the HLA-DQ molecule is shorter by eight amino acid residues than other major histocompatibility complex class II beta chains due to elimination of the fifth exon coding for part of the cytoplasmic domain. This elimination is caused by one base substitution in the splice acceptor site of the exon. We found that two HLA-DQB1 alleles, DQB1*0503 and DQB1*0601, did not have this substitution, and the exon was utilized in these two alleles. However, two forms of HLA-DQB mRNA, with or without exon 5, were generated in Epstein-Barr virus-transformed cell lines homozygous for DQB1*0503 or DQB1*0601, indicating alternative mRNA splicing. The alternative splicing of DQB1*0601 mRNA was also found in peripheral blood lymphocytes and L cell transfectants. To investigate the functional relevance of the allele-specific long cytoplasmic tail of HLA-DQ beta chain, we developed three types of L cell transfectants expressing exclusively the HLA-DQw6 molecules with short cytoplasmic tail, long cytoplasmic tail, or both forms of the beta chain, and used them as antigen presenting cells for streptococcal cell wall antigen-specific T cell lines. These three types of transfectants could function almost equally well as antigen presenting cells. It was thus demonstrated that both forms of HLA-DQ beta chain, with or without eight amino acid residues coded for by the exon 5, can be associated with the HLA-DQ alpha chain, be expressed on the cell surface, and function as restriction molecules in antigen recognition by the CD4+ T cells.