Expression of B7 costimulatory molecules by salivary gland epithelial cells in patients with Sjogren's syndrome. (1/1082)

OBJECTIVE: To investigate the expression of B7 costimulatory molecules in the lymphoepithelial lesions of salivary gland (SG) biopsy tissues and in SG epithelial cell lines derived from patients with Sjogren's syndrome (SS). METHODS: B7.1 and B7.2 protein expression was studied by immunohistochemistry in minor SGs obtained from 11 patients with SS and 10 disease control patients with nonspecific sialadenitis and in cultured SG epithelial cell lines obtained from minor SGs from 15 SS patients and 15 control patients. B7.1 and B7.2 messenger RNA (mRNA) expression by SG epithelial cell lines was examined by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: In biopsy tissues from SS patients, but not control patients, ductal and acinar epithelial cells showed increased expression of both B7.1 and B7.2. Intense spontaneous B7.1 protein expression (as well as HLA-ABC, but not B7.2 or HLA-DR) was also found in 73% of SG epithelial cell lines from SS patients versus 13% of those from control patients (P < 0.01). Interferon-y treatment induced, or up-regulated, B7.1, B7.2, and HLA-DR expression in all SG epithelial cell lines tested. B7.1 and B7.2 expression by SG epithelial cell lines was also verified at the mRNA level by RT-PCR. CONCLUSION: Human SG epithelia are intrinsically capable of expressing B7 proteins upon activation. In SS patients, the expression of B7 molecules by SG epithelial tissues and by SG epithelial cell lines indicates the activated status of SG epithelial cells in this disorder and, possibly, their capacity for presenting antigens to T cells.  (+info)

Natural variation of the expression of HLA and endogenous antigen modulates CTL recognition in an in vitro melanoma model. (2/1082)

Increasing attention has been devoted to elucidating the mechanism of lost or decreased expression of MHC or melanoma-associated antigens (MAAs), which may lead to tumor escape from immune recognition. Loss of expression of HLA class I or MAA has, as an undisputed consequence, loss of recognition by HLA class I-restricted cytotoxic T cells (CTLs). However, the relevance of down-regulation remains in question in terms of frequency of occurrence. Moreover the functional significance of epitope down-regulation, defining the relationship between MHC/epitope density and CTL interactions, is a matter of controversy, particularly with regard to whether the noted variability of expression of MHC/epitope occurs within a range likely to affect target recognition by CTLs. In this study, bulk metastatic melanoma cell lines originated from 25 HLA-A*0201 patients were analyzed for expression of HLA-A2 and MAAs. HLA-A2 expression was heterogeneous and correlated with lysis by CTLs. Sensitivity to lysis was also independently affected by the amount of ligand available for binding at concentrations of 0.001 to 1 mM. Natural expression of MAA was variable, independent from the expression of HLA-A*0201, and a significant co-factor determining recognition of melanoma targets. Thus, the naturally occurring variation in the expression of MAA and/or HLA documented by our in vitro results modulates recognition of melanoma targets and may (i) partially explain CTL-target interactions in vitro and (ii) elucidate potential mechanisms for progressive escape of tumor cells from immune recognition in vivo.  (+info)

Feasibility of immunotherapy of relapsed leukemia with ex vivo-generated cytotoxic T lymphocytes specific for hematopoietic system-restricted minor histocompatibility antigens. (3/1082)

Allogeneic bone marrow transplantation (BMT) is a common treatment of hematologic malignancies. Recurrence of the underlying malignancy is a major cause of treatment failure. Donor-derived cytotoxic T lymphocytes (CTLs) specific for patients' minor histocompatibility antigens (mHags) play an important role in both graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL) reactivities. mHags HA-1 and HA-2 induce HLA-A*0201-restricted CTLs in vivo and are exclusively expressed on hematopoietic cells, including leukemic cells and leukemic precursors, but not on fibroblasts, keratinocytes, or liver cells. The chemical nature of the mHags HA-1 and HA-2 is known. We investigated the feasibility of ex vivo generation of mHag HA-1- and HA-2-specific CTLs from unprimed mHag HA-1- and/or HA-2-negative healthy blood donors. HA-1 and HA-2 synthetic peptide-pulsed dendritic cells (DCs) were used as antigen-presenting cells (APC) to stimulate autologous unprimed CD8(+) T cells. The ex vivo-generated HA-1- and HA-2-specific CTLs efficiently lyse leukemic cells derived from acute myeloid leukemia (AML) and acute lymphoid leukemia (ALL) patients. No lytic reactivity was detected against nonhematopoietic cells. Sufficient numbers of the CTLs can be obtained for the adoptive immunotherapy purposes. In conclusion, we present a feasible, novel therapy for the treatment for relapsed leukemia after BMT with a low risk of GVHD.  (+info)

Assessment of immunogenicity of human Melan-A peptide analogues in HLA-A*0201/Kb transgenic mice. (4/1082)

Previous studies have shown that substitution of single amino acid residues in human Melan-A immunodominant peptides Melan-A27-35 and Melan-A26-35 greatly improved their binding and the stability of peptide/HLA-A*0201 complexes. In particular, one Melan-A peptide analogue was more efficient in the generation of Melan-A peptide-specific and melanoma-reactive CTL than its parental peptide in vitro from human PBL. In this study, we analyzed the in vivo immunogenicity of Melan-A natural peptides and their analogues in HLA-A*0201/Kb transgenic mice. We found that two human Melan-A natural peptides, Melan-A26-35 and Melan-A27-35, were relatively weak immunogens, whereas several Melan-A peptide analogues were potent immunogens for in vivo CTL priming. In addition, induced Melan-A peptide-specific mouse CTL cross-recognized natural Melan-A peptides and their analogues. More interestingly, these mouse CTL were also able to lyse human melanoma cell lines in vitro in a HLA-A*0201-restricted, Melan-A-specific manner. Our results indicate that the HLA-A*0201/Kb transgenic mouse is a useful animal model to perform preclinical testing of potential cancer vaccines, and that Melan-A peptide analogues are attractive candidates for melanoma immunotherapy.  (+info)

HLA alleles determine human T-lymphotropic virus-I (HTLV-I) proviral load and the risk of HTLV-I-associated myelopathy. (5/1082)

The risk of disease associated with persistent virus infections such as HIV-I, hepatitis B and C, and human T-lymphotropic virus-I (HTLV-I) is strongly determined by the virus load. However, it is not known whether a persistent class I HLA-restricted antiviral cytotoxic T lymphocyte (CTL) response reduces viral load and is therefore beneficial or causes tissue damage and contributes to disease pathogenesis. HTLV-I-associated myelopathy (HAM/TSP) patients have a high virus load compared with asymptomatic HTLV-I carriers. We hypothesized that HLA alleles control HTLV-I provirus load and thus influence susceptibility to HAM/TSP. Here we show that, after infection with HTLV-I, the class I allele HLA-A*02 halves the odds of HAM/TSP (P < 0.0001), preventing 28% of potential cases of HAM/TSP. Furthermore, HLA-A*02(+) healthy HTLV-I carriers have a proviral load one-third that (P = 0.014) of HLA-A*02(-) HTLV-I carriers. An association of HLA-DRB1*0101 with disease susceptibility also was identified, which doubled the odds of HAM/TSP in the absence of the protective effect of HLA-A*02. These data have implications for other persistent virus infections in which virus load is associated with prognosis and imply that an efficient antiviral CTL response can reduce virus load and so prevent disease in persistent virus infections.  (+info)

The lifespan of major histocompatibility complex class I/peptide complexes determines the efficiency of cytotoxic T-lymphocyte responses. (6/1082)

Major histocompatibility complex (MHC)/peptide association and stability are determined by specific amino acid interactions between peptide antigens and the MHC groove, and are regarded as a critical feature in ensuring efficient monitoring by T cells. In this investigation we examined the relationship between MHC/peptide stability and the immunostimulatory capacity of MHC/peptide complexes. For this purpose we compared synthetic peptide analogues derived from the immunodominant HLA-A11-presented IVTDFSVIK (IVT) epitope, for their capacity to reactivate IVT-specific memory cytotoxic T-lymphocyte (CTL) responses. The analogues differentiated from the wild-type epitope by single amino acid substitution at position 2. All peptides showed similar affinity for HLA-A11 molecules and were recognized by IVT-specific CTL clones, but induced HLA-A11 complexes at the cell surface with different lifespan. This model offered the possibility of comparing the capacity of an immunogenic epitope to stimulate a unique population of T-cell precursors depending on the lifespan of its presentation at the cell surface. We demonstrated that stable HLA-A11/peptide complexes efficiently stimulate IVT-specific CTL responses, while HLA-A11/peptide complexes with short lifespan do not. The precise identification of the role of amino acid residues in the formation of stable MHC/peptide complexes may be relevant for the design of wild-type-derived epitopes with high immunogenicity. These analogues may have important applications in the immunotherapy of infectious diseases and immunogenic tumours.  (+info)

Differences in gene conversion rates among exons between HLA-A and HLA-B loci. (7/1082)

To examine whether gene conversion occurs between two homologous loci of HLA-A and HLA-B, DNA sequences were compared and the differences or the numbers of substitutions per site at synonymous and nonsynonymous sites were calculated in the coding region and in the non-coding region. (1) Totally differences at synonymous sites in introns and coding regions are small as compared with the differences in the 5' flanking region. This indicates that gene conversion should occur between HLA-A and HLA-B loci. (2) In exon2 and exon3, the differences at synonymous sites are smaller than at nonsynonymous sites. This suggests that these exons are subject to positive natural selection, which is consistent with the reports of Hughes and Nei [1,2], because exon2 and exon3 encode alpha 1 and alpha 2 domains of the HLA molecule respectively which include mainly the antigen recognition sites (ARS). (3) in exon4, the difference at the synonymous site is the same as that in the 5' flanking region, which suggests that gene conversion does not frequently occur. The difference in this exon is extremely small at the nonsynonymous sites. This exon encodes the alpha 3 domain which does not have the antigen recognition sites but have an important function in maintaining the structure of the HLA molecule. From the above results, it can be concluded that gene conversion between HLA-A and HLA-B occurs more frequently in the two exons, exon2 and exon3 which have ARS regions. Furthermore, to examine a possibility that the variability of GC content along sequence influences the difference, the GC content was calculated along the sequence.  (+info)

Biosynthesis of HLA-C heavy chains in melanoma cells with multiple defects in the expression of HLA-A, -B, -C molecules. (8/1082)

Recent investigations have shown that malignant transformation may down-regulate the expression of class I HLA molecules, beta2-microglobulin (beta2m) and members of the antigen-processing machinery. In the present study, we HLA-genotyped and identified at a biochemical level the three (HLA-A25, -B8, -Cw7) class I alleles expressed by the previously described [D'Urso CM et al (1992) J Clin Invest 87: 284-292] beta2m-defective human melanoma FO-1 cell line and tested their ability to interact with calnexin, calreticulin and the TAP (transporter associated with antigen processing) complex. All these alleles were found to bind calnexin, but not calreticulin or the poorly expressed TAP complex, both in parental and beta2m-transfected FO-1 cells, demonstrating a complex defect of class I expression in FO-1 cells. In these conditions, Cw7 heavy chains interacted with calnexin more strongly than A25 and B8, and preferentially accumulated in the endoplasmic reticulum, in both a calnexin-associated and a calnexin-free form. In addition, they could be transported to the cell surface at low levels even in the absence of beta2m, without undergoing terminal glycosylation. These results establish a parallel between HLA-C and the murine Db and Ld molecules which have been found to be surface expressed and functional in beta2m-defective cells. They also demonstrate distinctive features of HLA-C molecules. We propose that the accumulation of several assembly intermediates of HLA-C might favour the binding of peptide antigens not readily bound by HLA-A and -B molecules in neoplastic cells with suboptimal class I expression.  (+info)