scholarly journals Spectrum and Clinical Significance of HLA Class I Alleles and Their Somatic Mutations in Immune Aplastic Anemia

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 3738-3738
Author(s):  
Yoshitaka Zaimoku ◽  
Sharon D. Adams ◽  
Bhavisha A Patel ◽  
Audrey Ai Chin Lee ◽  
Sachiko Kajigaya ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Cell Surface ◽  
Aplastic Anemia ◽  
Clinical Significance ◽  
Somatic Mutations ◽  
Clonal Evolution ◽  
Hla Class I ◽  
Surface Expression ◽  
Class I ◽  
Cell Surface Expression

Clonal hematopoiesis associated with loss of HLA class I alleles due to somatic mutations and/or 6p loss of heterozygosity (LOH) is frequent in immune aplastic anemia (AA). HLA-B*40:02 is more likely to be involved in HLA loss in Japanese AA patients, suggesting a role for this allele in immune pathophysiology (Zaimoku Y et al, Blood 2017). Mutations in non-B*40:02 HLA class I alleles have been reported in a limited number of patients from the United States (Babushok D et al, Blood Adv 2017) and Japan (Mizumaki H et al, 60th ASH meeting), but their prevalence and clinical significance are not well characterized. We investigated somatic mutations of HLA class I alleles, HLA allele frequencies, and their correlations with outcomes of therapy in a total of 532 AA patients, aged 2 years or older, treated on various Hematology Branch protocols (clinicaltrials.gov NCTs 00001964, 00061360, 00195624, 00260689, 00944749, 01193283, and 01623167). HLA allele-lacking (HLA-) monocytes from cryopreserved peripheral blood mononuclear cells were screened by flow cytometry after staining with allele-specific monoclonal antibodies for HLA-A and/or HLA-B (HLA-flow) in 172 AA patients. HLA- monocytes accounting for 0.5% to 100% (median 9.5%) of total monocytes were detected in 49 (28%) of the 172 patients and in 59 (15%) of 382 alleles analyzed (Figure 1). Loss of cell surface expression was frequent for HLA-B14 (46%), B27 (33%), B49 (33%), A68 (26%), A2 (23%), B40 (21%), and B8 (21%). One percent to 60% (median, 8.9%) of glycosylphosphatidylinositol-linked protein-negative (GPI-) monocytes were also present in 43% (21 of 49) of the patients with HLA- monocytes, but GPI- clones had normal HLA cell surface expression. Deep sequencing of HLA-A, HLA-B and HLA-C on sorted HLA- and HLA+GPI+ monocytes was performed in 42 of the 48 patients from whom adequate cells were available. Somatic mutations and/or LOH corresponding to the lacking alleles were detected in all 42 cases (Figure 1): 9 had both somatic mutations and LOH, 20 had somatic mutations only, and 13 had LOH only. Among the 13 patients who showed only LOH in the absent allele, 6 had somatic mutations in other alleles of HLA+ monocytes that was not analyzable of HLA expression, and 2 had a breakpoint of LOH between HLA-A and HLA-C, leading to loss of a single HLA-A allele. Somatic mutations or LOH involving only one allele were present in 37 patients among 6 HLA-A alleles (in 02:01 [7 patients], 02:05 [1], 02:06 [3], 02:11 [1], 68:01 [2], 68:02 [2]) and 10 HLA-B alleles (07:02 [1], 08:01 [4], 14:01 [1], 14:02 [7], 27:05 [1], 35:02 [1], 35:05 [1], 40:01 [1], 40:02 [3], 45:01 [1]), but were not found in HLA-C alleles. HLA allele frequencies in AA patients, including 271 white Americans, 120 African-Americans, and 99 Hispanics and Latinos, were compared with ethnicity-matched individuals in bone marrow donor datasets of the National Marrow Donor Program, and underwent random-effects meta-analyses. HLA-B*07, B*14, and B*40 were overrepresented in AA, while A*02, A*68, and B*08 frequencies were similar to those of healthy donors (Figure 2). In 164 severe AA patients who were initially treated with horse antithymocyte globulin (hATG), cyclosporine, and eltrombopag between 2012 and 2018, 36 and 79 were positive and negative for HLA- monocytes, respectively, and 49 were not tested by HLA-flow. There was no significant difference in overall and complete response rates at six months among the three groups (Figure 3). Clonal evolution, defined as acquisition of abnormal bone marrow cytogenetics or morphology, especially high-risk evolution to chromosome 7 abnormalities, complex cytogenetics, or morphological MDS/AML, tended to be more frequent in patients with HLA- monocytes, compared to the other two groups, but the difference did not reach statistical significance. Clinical outcomes were also assessed according to the presence of specific HLA alleles in 400 severe AA patients who were treated with hATG-based initial immunosuppressive therapy from 2000 to 2018: there was no significant differences in probabilities of response and clonal evolution according to the alleles associated with somatic mutations. Our study revealed that somatic mutations in HLA genes in AA are broadly distributed, but some alleles are preferentially affected. Inconsistent with previous studies, we found that outcomes of therapy did not significantly correlate with HLA gene mutations or with distinct HLA alleles. Disclosures No relevant conflicts of interest to declare.

The Clinical Significance of Some Specific HLA Class I Alleles in Japanese Patients with Bone Marrow Failure (BMF).

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1040-1040
Author(s):  
Hideyoshi Noji ◽  
Tsutomu Shichishima ◽  
Kazuhiko Ikeda ◽  
Akiko Nakamura ◽  
Kazuko Akutsu ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Lactate Dehydrogenase ◽  
T Lymphocytes ◽  
Aplastic Anemia ◽  
Clinical Significance ◽  
Bone Marrow Failure ◽  
Hla Class I ◽  
Japanese Patients ◽  
Class I ◽  
Immune Mechanisms

Abstract Autoreactive T lymphocytes are implicated in the immune mechanisms involved in the bone marrow failure (BMF) syndrome, including aplastic anemia (AA), paroxysmal nocturnal hemoglobinuria (PNH), and myelodysplastic syndrome (MDS). However, the significance of the HLA class I alleles remains unknown in the BMF syndrome. Nevertheless, from many clinical and basic studies, it is certain that CD8+ T lymphocytes are implicated in some of the immune mechanisms involved in the occurrence of AA. To clarify some clinical significance of the HLA class I alleles in the BMF syndrome, we investigated the alleles using a high-resolution method of genotyping in 78 Japanese patients with BMF, including 32 AA, 24 PNH, and 22 MDS patients. Subsequently, we compared various clinical findings, including age, sex, white blood cell counts, absolute neutrophil counts, hemoglobin concentrations, reticulocyte counts, platelet counts, values of lactate dehydrogenase, durations of illness, chromosomal findings, and proportions of CD55− and CD59− erythrocytes, between the groups with and without some alleles. The diagnosis and grading of the severity of AA were based on the criteria of the International Agranulocytosis and Aplastic Anemia Study Group (Blood1987; 70: 1718–21) and that of Frickhofen et al (N Engl J Med1991; 324: 1297–304), respectively. A patient with a CD55− and CD59− population of more than 1% was judged to have PNH erythrocytes (Blood1996; 87: 5332–40). The diagnosis of MDS was determined according to the FAB criteria (Br J Haematol1982; 51: 189–99). The frequencies of the HLA-B* 4002 allele in AA patients (21.9%) and of the HLA-A* 0206 allele in PNH patients (22.9%) were significantly different from those in controls (n=371; 8.6%, p<0.002 and 7.7%, p<0.001, respectively), while we found no specific HLA class I alelles in MDS patients. The frequency of the HLA-DRB1*1501 allele in PNH patients (31.3%) was significantly higher than that in controls (6.1%, p<0.0001), while we could not find the high frequencies of the HLA-DRB1*1501 (10.9%) and *1502 (10.9%) alleles in AA patients. The proportion of severe or very severe AA patients with the HLA-B* 4002 allele (10/17, 58.8%) was significantly higher than that of non-severe AA patients with the allele (3/15, 20%; p<0.05). In contrast, the proportion of severe or very severe AA patients (4/17; 23.5%) with the HLA-DRB1* 1501 allele was not different from that of non-severe AA patients (3/15; 20%) with the allele. Subsequently, the reticulocyte counts (138 ± 73 x 10 9/L) and values of lactate dehydrogenase (2399 ± 235 IU/L) at the time of examination in PNH patients (n=10) with the HLA-A* 0206 allele were significantly higher than those in PNH patients (n=14) without the allele (78 ± 34 x 109/L, p<0.02 and 972 ± 770 IU/L, p<0.05, respectively). In addition, the frequency of PNH patients with over 30% of complement-sensitive erythrocytes, consisting of intermediate and negative populations of CD55 and CD59 expressions on erythrocytes by flow cytometry, was significantly higher in PNH patients with the HLA-A* 0206 than in those without the allele (80% versus 28.6%, p<0.05). In conclusions, our results suggest that the HLA-B* 4002 allele in AA or the HLA-A* 0206 allele in PNH is related to grading of the severity of AA or grading of hemolysis of PNH, respectively.

scholarly journals A brief, but comprehensive, guide to clonal evolution in aplastic anemia

Hematology ◽  
2018 ◽  
Vol 2018 (1) ◽  
pp. 457-466 ◽  
Author(s):  
Daria V. Babushok
Keyword(s):  
Aplastic Anemia ◽  
Somatic Mutations ◽  
Clonal Evolution ◽  
Clinical Care ◽  
Hla Class I ◽  
The Elderly ◽  
Hematologic Malignancies ◽  
Class I ◽  
Clonal Hematopoiesis ◽  
Immune Mediated

Abstract Acquired aplastic anemia (AA) is an immune-mediated bone marrow aplasia that is strongly associated with clonal hematopoiesis upon marrow recovery. More than 70% of AA patients develop somatic mutations in their hematopoietic cells. In contrast to other conditions linked to clonal hematopoiesis, such as myelodysplastic syndrome (MDS) or clonal hematopoiesis of indeterminate potential in the elderly, the top alterations in AA are closely related to its immune pathogenesis. Nearly 40% of AA patients carry somatic mutations in the PIGA gene manifested as clonal populations of cells with the paroxysmal nocturnal hemoglobinuria phenotype, and 17% of AA patients have loss of HLA class I alleles. It is estimated that between 20% and 35% of AA patients have somatic mutations associated with hematologic malignancies, most characteristically in the ASXL1, BCOR, and BCORL1 genes. Risk factors for evolution to MDS in AA include the duration of disease, acquisition of high-risk somatic mutations, and age at AA onset. Emerging data suggest that several HLA class I alleles not only predispose to the development of AA but may also predispose to clonal evolution in AA patients. Long-term prospective studies are needed to determine the true prognostic implications of clonal hematopoiesis in AA. This article provides a brief, but comprehensive, review of our current understanding of clonal evolution in AA and concludes with 3 cases that illustrate a practical approach for integrating results of next-generation molecular studies into the clinical care of AA patients in 2018.

scholarly journals Impaired intracellular transport and cell surface expression of nonpolymorphic HLA-E: evidence for inefficient peptide binding.

1992 ◽  
Vol 176 (4) ◽  
pp. 1083-1090 ◽  
Author(s):  
M Ulbrecht ◽  
J Kellermann ◽  
J P Johnson ◽  
E H Weiss
Keyword(s):  
Cell Surface ◽  
Intracellular Transport ◽  
Hla Class I ◽  
Surface Expression ◽  
Myeloma Cell ◽  
Peptide Ligands ◽  
Class I ◽  
Cell Surface Expression ◽  
Trimolecular Complex ◽  
Beta 2 Microglobulin

The assembly of the classical, polymorphic major histocompatibility complex class I molecules in the endoplasmic reticulum requires the presence of peptide ligands and beta 2-microglobulin (beta 2m). Formation of this trimolecular complex is a prerequisite for efficient transport to the cell surface, where presented peptides are scanned by T lymphocytes. The function of the other class I molecules is in dispute. The human, nonclassical class I gene, HLA-E, was found to be ubiquitously transcribed, whereas cell surface expression was difficult to detect upon transfection. Pulse chase experiments revealed that the HLA-E heavy chain in transfectants, obtained with the murine myeloma cell line P3X63-Ag8.653 (X63), displays a significant reduction in oligosaccharide maturation and intracellular transport compared with HLA-B27 in corresponding transfectants. The accordingly low HLA-E cell surface expression could be significantly enhanced by either reducing the culture temperature or by supplementing the medium with human beta 2m, suggesting inefficient binding of endogenous peptides to HLA-E. To analyze whether HLA-E binds peptides and to identify the corresponding ligands, fractions of acid-extracted material from HLA-E/X63 transfectants were separated by reverse phase HPLC and were tested for their ability to enhance HLA-E cell surface expression. Two fractions specifically increased the HLA class I expression on the HLA-E transfectant clone.

scholarly journals Variations in HLA-B cell surface expression, half-life and extracellular antigen receptivity

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Brogan Yarzabek ◽  
Anita J Zaitouna ◽  
Eli Olson ◽  
Gayathri N Silva ◽  
Jie Geng ◽  
...  
Keyword(s):  
Cell Surface ◽  
Half Life ◽  
Antigen Processing ◽  
Human Lymphocytes ◽  
Hla Class I ◽  
Surface Expression ◽  
Class I ◽  
Cell Surface Expression ◽  
Specific Expression ◽  
Hla Class I Molecules

The highly polymorphic human leukocyte antigen (HLA) class I molecules present peptide antigens to CD8+ T cells, inducing immunity against infections and cancers. Quality control mediated by peptide loading complex (PLC) components is expected to ensure the cell surface expression of stable peptide-HLA class I complexes. This is exemplified by HLA-B*08:01 in primary human lymphocytes, with both expression level and half-life at the high end of the measured HLA-B expression and stability hierarchies. Conversely, low expression on lymphocytes is measured for three HLA-B allotypes that bind peptides with proline at position 2, which are disfavored by the transporter associated with antigen processing. Surprisingly, these lymphocyte-specific expression and stability differences become reversed or altered in monocytes, which display larger intracellular pools of HLA class I than lymphocytes. Together, the findings indicate that allele and cell-dependent variations in antigen acquisition pathways influence HLA-B surface expression levels, half-lives and receptivity to exogenous antigens.

scholarly journals Variations in MHC class I antigen presentation and immunopeptidome selection pathways

F1000Research ◽  
2020 ◽  
Vol 9 ◽  
pp. 1177
Author(s):  
Anita J. Zaitouna ◽  
Amanpreet Kaur ◽  
Malini Raghavan
Keyword(s):  
Cell Surface ◽  
Antigen Presentation ◽  
Surface Expression ◽  
Structural Features ◽  
Class I ◽  
Cell Surface Expression ◽  
Immune Recognition ◽  
Antigen Receptors ◽  
Class I Mhc ◽  
Mhc I

Major histocompatibility class I (MHC-I) proteins mediate immunosurveillance against pathogens and cancers by presenting antigenic or mutated peptides to antigen receptors of CD8+ T cells and by engaging receptors of natural killer (NK) cells. In humans, MHC-I molecules are highly polymorphic. MHC-I variations permit the display of thousands of distinct peptides at the cell surface. Recent mass spectrometric studies have revealed unique and shared characteristics of the peptidomes of individual MHC-I variants. The cell surface expression of MHC-I–peptide complexes requires the functions of many intracellular assembly factors, including the transporter associated with antigen presentation (TAP), tapasin, calreticulin, ERp57, TAP-binding protein related (TAPBPR), endoplasmic reticulum aminopeptidases (ERAPs), and the proteasomes. Recent studies provide important insights into the structural features of these factors that govern MHC-I assembly as well as the mechanisms underlying peptide exchange. Conformational sensing of MHC-I molecules mediates the quality control of intracellular MHC-I assembly and contributes to immune recognition by CD8 at the cell surface. Recent studies also show that several MHC-I variants can follow unconventional assembly routes to the cell surface, conferring selective immune advantages that can be exploited for immunotherapy.

Ku80 autoantigen as a cellular coreceptor for human parvovirus B19 infection

Blood ◽  
2005 ◽  
Vol 106 (10) ◽  
pp. 3449-3456 ◽  
Author(s):  
Yasuhiko Munakata ◽  
Takako Saito-Ito ◽  
Keiko Kumura-Ishii ◽  
Jie Huang ◽  
Takao Kodera ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Cell Surface ◽  
Cell Lines ◽  
Bone Marrow Cells ◽  
Parvovirus B19 ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Human Parvovirus B19 ◽  
Erythroid Cells ◽  
Interfering Rna

AbstractHuman parvovirus B19 (B19) infects human erythroid cells expressing P antigen. However, some cell lines that were positive for P antigen failed to bind B19, whereas some cell lines had an ability to bind B19 despite undetectable expression of P antigen. We here demonstrate that B19 specifically binds with Ku80 autoantigen on the cell surface. Furthermore, transfection of HeLa cells with the gene of Ku80 enabled the binding of B19 and allowed its entry into cells. Moreover, reduction of cell-surface expression of Ku80 in KU812Ep6 cells, which was a high-sensitive cell line for B19 infection, by short interfering RNA for Ku80 resulted in the marked inhibition of B19 binding in KU812Ep6 cells. Although Ku80 originally has been described as a nuclear protein, human bone marrow erythroid cells with glycophorin A or CD36, B cells with CD20, or T cells with CD3 were all positive for cell-surface expression of Ku80. B19 infection of KU812Ep6 cells and bone marrow cells was inhibited in the presence of anti-Ku80 antibody. Our data suggest that Ku80 functions as a novel coreceptor for B19 infection, and this finding may provide an explanation for the pathologic immunity associated with B19 infection.

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