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Ravindranath MH, Ravindranath NM, Amato-Menker CJ, Hilali FE, Filippone EJ. Conformational Alterations of the Cell Surface of Monomeric and Dimeric β2m-Free HLA-I (Proto-HLA) May Enable Novel Immune Functions in Health and Disease. Curr Issues Mol Biol 2024; 46:6961-6985. [PMID: 39057057 PMCID: PMC11276036 DOI: 10.3390/cimb46070416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2024] [Revised: 06/21/2024] [Accepted: 06/28/2024] [Indexed: 07/28/2024] Open
Abstract
Human leukocyte antigens (HLAs) are polymorphic glycoproteins expressed on the cell surface of nucleated cells and consist of two classes, HLA class I and HLA class II. In contrast, in mice, these molecules, known as H-2, are expressed on both nucleated cells and erythrocytes. HLA-I molecules (Face-1) are heterodimers consisting of a polypeptide heavy chain (HC) and a light chain, B2-microglobulin (B2m). The heterodimers bind to antigenic peptides and present them to the T-cell receptors of CD8+ cytotoxic T lymphocytes. The HCs can also independently emerge on the cell surface as B2m-free HC monomers without peptides (Face-2). Early investigators suggested that the occurrence of B2m-free HCs on the cell surface resulted from the dissociation of B2m from Face-1. However, others documented the independent emergence of B2m-free HCs (Face-2) from the endoplasmic reticulum (ER) to the cell surface. The clustering of such HC molecules on either the cell surface or on exosomes resulted in the dimerization of B2m-free HCs to form homodimers (if the same allele, designated as Face-3) or heterodimers (if different alleles, designated as Face-4). Face-2 occurs at low levels on the cell surface of several normal cells but is upregulated on immune cells upon activation by proinflammatory cytokines and other agents such as anti-CD3 antibodies, phytohemagglutinin, and phorbol myristate acetate. Their density on the cell surface remains high as long as the cells remain activated. After activation-induced upregulation, Face-2 molecules undergo homo- and heterodimerization (Face-3 and Face-4). Observations made on the structural patterns of HCs and their dimerization in sharks, fishes, and tetrapod species suggest that the formation of B2m-free HC monomers and dimers is a recapitalization of a phylogenetically conserved event, befitting the term Proto-HLA for the B2m-free HCs. Spontaneous arthritis occurs in HLA-B27+ mice lacking B2m (HLA-B27+ B2m-/-) but not in HLA-B27+ B2m+/+ mice. Anti-HC-specific monoclonal antibodies (mAbs) delay disease development. Some HLA-I polyreactive mAbs (MEM series) used for immunostaining confirm the existence of B2m-free variants in several cancer cells. The conformational alterations that occur in the B2m-free HCs enable them to interact with several inhibitory and activating receptors of cellular components of the innate (natural killer (NK) cells) and adaptive (T and B cells) immune systems. The NK cells express killer immunoglobulin-like receptors (KIRs), whereas leukocytes (T and B lymphocytes, monocytes/macrophages, and dendritic cells) express leukocyte immunoglobulin-like receptors (LILRs). The KIRs and LILRs include activating and inhibitory members within their respective groups. This review focuses on the interaction of KIRs and LILRs with B2m-free HC monomers and dimers in patients with spondylarthritis. Several investigations reveal that the conformational alterations occurring in the alpha-1 and alpha-2 domains of B2m-free HCs may facilitate immunomodulation by their interaction with KIR and LILR receptors. This opens new avenues to immunotherapy of autoimmune diseases and even human cancers that express B2m-free HCs.
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Affiliation(s)
- Mepur H. Ravindranath
- Department of Hematology and Oncology, Children’s Hospital, Los Angeles, CA 90027, USA
- Terasaki Foundation Laboratory, Santa Monica, CA 90064, USA
| | - Narendranath M. Ravindranath
- Norris Dental Science Center, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90089, USA;
| | - Carly J. Amato-Menker
- Department of Microbiology, Immunology and Cell Biology, School of Medicine, West Virginia University, Morgantown, WV 26506, USA;
| | - Fatiha El Hilali
- Medico-Surgical, Biomedicine and Infectiology Research Laboratory, The Faculty of Medicine and Pharmacy of Laayoune & Agadir, Ibnou Zohr University, Agadir 80000, Morocco;
| | - Edward J. Filippone
- Division of Nephrology, Department of Medicine, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19145, USA;
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Ravindranath MH, El Hilali F, Amato-Menker CJ, El Hilali H, Selvan SR, Filippone EJ. Role of HLA-I Structural Variants and the Polyreactive Antibodies They Generate in Immune Homeostasis. Antibodies (Basel) 2022; 11:antib11030058. [PMID: 36134954 PMCID: PMC9495617 DOI: 10.3390/antib11030058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2022] [Revised: 08/24/2022] [Accepted: 08/31/2022] [Indexed: 11/29/2022] Open
Abstract
Cell-surface HLA-I molecules consisting of β2-microglobulin (β2m) associated heavy chains (HCs), referred to as Face-1, primarily present peptides to CD8+ T-cells. HCs consist of three α-domains, with selected amino acid sequences shared by all alleles of all six isoforms. The cell-surface HLA undergoes changes upon activation by pathological conditions with the expression of β2m-free HCs (Face-2) resulting in exposure of β2m-masked sequences shared by almost all alleles and the generation of HLA-polyreactive antibodies (Abs) against them. Face-2 may homodimerize or heterodimerize with the same (Face-3) or different alleles (Face-4) preventing exposure of shared epitopes. Non-allo immunized males naturally carry HLA-polyreactive Abs. The therapeutic intravenous immunoglobulin (IVIg) purified from plasma of thousands of donors contains HLA-polyreactive Abs, admixed with non-HLA Abs. Purified HLA-polyreactive monoclonal Abs (TFL-006/007) generated in mice after immunizing with Face-2 are documented to be immunoregulatory by suppressing or activating different human lymphocytes, much better than IVIg. Our objectives are (a) to elucidate the complexity of the HLA-I structural variants, and their Abs that bind to both shared and uncommon epitopes on different variants, and (b) to examine the roles of those Abs against HLA-variants in maintaining immune homeostasis. These may enable the development of personalized therapeutic strategies for various pathological conditions.
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Affiliation(s)
- Mepur H. Ravindranath
- Department of Hematology and Oncology, Children’s Hospital, Los Angeles, CA 90027, USA
- Emeritus Research Scientist, Terasaki Foundation Laboratory, Santa Monica, CA 90064, USA
- Correspondence:
| | - Fatiha El Hilali
- Medico-Surgical, Biomedicine and Infectiology Research Laboratory, The Faculty of Medicine and Pharmacy of Laayoune & Agadir, Ibn Zohr University, Agadir 80000, Morocco
| | - Carly J. Amato-Menker
- Department of Microbiology, Immunology, and Cell Biology, School of Medicine, West Virginia University, Morgantown, WV 26506, USA
| | - Hajar El Hilali
- Medico-Surgical, Biomedicine and Infectiology Research Laboratory, The Faculty of Medicine and Pharmacy of Laayoune & Agadir, Ibn Zohr University, Agadir 80000, Morocco
| | - Senthamil R. Selvan
- Division of Immunology and Hematology Devices, OHT 7: Office of In Vitro Diagnostics, Office of Product Evaluation and Quality, Center for Devices and Radiological Health, Food and Drug Administration (FDA), Silver Spring, MD 20993, USA
| | - Edward J. Filippone
- Division of Nephrology, Department of Medicine, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19145, USA
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Ravindranath MH, Ravindranath NM, Selvan SR, Filippone EJ, Amato-Menker CJ, El Hilali F. Four Faces of Cell-Surface HLA Class-I: Their Antigenic and Immunogenic Divergence Generating Novel Targets for Vaccines. Vaccines (Basel) 2022; 10:vaccines10020339. [PMID: 35214796 PMCID: PMC8878457 DOI: 10.3390/vaccines10020339] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 02/07/2022] [Accepted: 02/17/2022] [Indexed: 12/19/2022] Open
Abstract
Leukocyte cell-surface HLA-I molecules, involved in antigen presentation of peptides to CD8+ T-cells, consist of a heavy chain (HC) non-covalently linked to β2-microglobulin (β2m) (Face-1). The HC amino acid composition varies across all six isoforms of HLA-I, while that of β2m remains the same. Each HLA-allele differs in one or more amino acid sequences on the HC α1 and α2 helices, while several sequences among the three helices are conserved. HCs without β2m (Face-2) are also observed on human cells activated by malignancy, viral transformation, and cytokine or chemokine-mediated inflammation. In the absence of β2m, the monomeric Face-2 exposes immunogenic cryptic sequences on these cells as confirmed by HLA-I monoclonal antibodies (LA45, L31, TFL-006, and TFL-007). Furthermore, such exposure enables dimerization between two Face-2 molecules by SH-linkage, salt linkage, H-bonding, and van der Waal forces. In HLA-B27, the linkage between two heavy chains with cysteines at position of 67 of the amino acid residues was documented. Similarly, several alleles of HLA-A, B, C, E, F and G express cysteine at 67, 101, and 164, and additionally, HLA-G expresses cysteine at position 42. Thus, the monomeric HC (Face-2) can dimerize with another HC of its own allele, as homodimers (Face-3), or with a different HC-allele, as heterodimers (Face-4). The presence of Face-4 is well documented in HLA-F. The post-translational HLA-variants devoid of β2m may expose several cryptic linear and non-linear conformationally altered sequences to generate novel epitopes. The objective of this review, while unequivocally confirming the post-translational variants of HLA-I, is to highlight the scientific and clinical importance of the four faces of HLA and to prompt further research to elucidate their functions and their interaction with non-HLA molecules during inflammation, infection, malignancy and transplantation. Indeed, these HLA faces may constitute novel targets for passive and active specific immunotherapy and vaccines.
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Affiliation(s)
- Mepur H. Ravindranath
- Department of Hematology and Oncology, Children’s Hospital, Los Angeles, CA 90027, USA
- Emeritus Research Scientist at Terasaki Foundation Laboratory, Santa Monica, CA 90064, USA
- Correspondence:
| | - Narendranath M. Ravindranath
- Norris Dental Science Center, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90089, USA;
| | | | - Edward J. Filippone
- Division of Nephrology, Department of Medicine, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19145, USA;
| | - Carly J. Amato-Menker
- Department of Microbiology, Immunology and Cell Biology, School of Medicine, West Virginia University, Morgantown, WV 26506, USA;
| | - Fatiha El Hilali
- The Faculty of Medicine and Pharmacy of Laayoune, Ibn Zohr University, Agadir 70000, Morocco;
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Ravindranath MH, El Hilali F, Filippone EJ. The Impact of Inflammation on the Immune Responses to Transplantation: Tolerance or Rejection? Front Immunol 2021; 12:667834. [PMID: 34880853 PMCID: PMC8647190 DOI: 10.3389/fimmu.2021.667834] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Accepted: 10/11/2021] [Indexed: 12/21/2022] Open
Abstract
Transplantation (Tx) remains the optimal therapy for end-stage disease (ESD) of various solid organs. Although alloimmune events remain the leading cause of long-term allograft loss, many patients develop innate and adaptive immune responses leading to graft tolerance. The focus of this review is to provide an overview of selected aspects of the effects of inflammation on this delicate balance following solid organ transplantation. Initially, we discuss the inflammatory mediators detectable in an ESD patient. Then, the specific inflammatory mediators found post-Tx are elucidated. We examine the reciprocal relationship between donor-derived passenger leukocytes (PLs) and those of the recipient, with additional emphasis on extracellular vesicles, specifically exosomes, and we examine their role in determining the balance between tolerance and rejection. The concept of recipient antigen-presenting cell "cross-dressing" by donor exosomes is detailed. Immunological consequences of the changes undergone by cell surface antigens, including HLA molecules in donor and host immune cells activated by proinflammatory cytokines, are examined. Inflammation-mediated donor endothelial cell (EC) activation is discussed along with the effect of donor-recipient EC chimerism. Finally, as an example of a specific inflammatory mediator, a detailed analysis is provided on the dynamic role of Interleukin-6 (IL-6) and its receptor post-Tx, especially given the potential for therapeutic interdiction of this axis with monoclonal antibodies. We aim to provide a holistic as well as a reductionist perspective of the inflammation-impacted immune events that precede and follow Tx. The objective is to differentiate tolerogenic inflammation from that enhancing rejection, for potential therapeutic modifications. (Words 247).
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Affiliation(s)
- Mepur H. Ravindranath
- Department of Hematology and Oncology, Children’s Hospital, Los Angeles, CA, United States
- Terasaki Foundation Laboratory, Santa Monica, CA, United States
| | | | - Edward J. Filippone
- Division of Nephrology, Department of Medicine, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA, United States
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Arosa FA, Esgalhado AJ, Reste-Ferreira D, Cardoso EM. Open MHC Class I Conformers: A Look through the Looking Glass. Int J Mol Sci 2021; 22:ijms22189738. [PMID: 34575902 PMCID: PMC8470049 DOI: 10.3390/ijms22189738] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 09/04/2021] [Accepted: 09/08/2021] [Indexed: 12/16/2022] Open
Abstract
Studies carried out during the last few decades have consistently shown that cell surface MHC class I (MHC-I) molecules are endowed with functions unrelated with antigen presentation. These include cis–trans-interactions with inhibitory and activating KIR and LILR, and cis-interactions with receptors for hormones, growth factors, cytokines, and neurotransmitters. The mounting body of evidence indicates that these non-immunological MHC-I functions impact clinical and biomedical settings, including autoimmune responses, tumor escape, transplantation, and neuronal development. Notably, most of these functions appear to rely on the presence in hematopoietic and non-hematopoietic cells of heavy chains not associated with β2m and the peptide at the plasma membrane; these are known as open MHC-I conformers. Nowadays, open conformers are viewed as functional cis-trans structures capable of establishing physical associations with themselves, with other surface receptors, and being shed into the extracellular milieu. We review past and recent developments, strengthening the view that open conformers are multifunctional structures capable of fine-tuning cell signaling, growth, differentiation, and cell communication.
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Affiliation(s)
- Fernando A Arosa
- Health Sciences Research Center (CICS-UBI), University of Beira Interior, 6200-506 Covilhã, Portugal
- Faculty of Health Sciences, University of Beira Interior, 6200-506 Covilhã, Portugal
| | - André J Esgalhado
- Health Sciences Research Center (CICS-UBI), University of Beira Interior, 6200-506 Covilhã, Portugal
| | - Débora Reste-Ferreira
- Health Sciences Research Center (CICS-UBI), University of Beira Interior, 6200-506 Covilhã, Portugal
| | - Elsa M Cardoso
- Health Sciences Research Center (CICS-UBI), University of Beira Interior, 6200-506 Covilhã, Portugal
- Faculty of Health Sciences, University of Beira Interior, 6200-506 Covilhã, Portugal
- Health School, Guarda Polytechnic Institute, 6300-749 Guarda, Portugal
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Ravindranath MH, Hilali FE, Filippone EJ. Therapeutic Potential of HLA-I Polyreactive mAbs Mimicking the HLA-I Polyreactivity and Immunoregulatory Functions of IVIg. Vaccines (Basel) 2021; 9:680. [PMID: 34205517 PMCID: PMC8235337 DOI: 10.3390/vaccines9060680] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 06/03/2021] [Accepted: 06/05/2021] [Indexed: 12/12/2022] Open
Abstract
HLA class-I (HLA-I) polyreactive monoclonal antibodies (mAbs) reacting to all HLA-I alleles were developed by immunizing mice with HLA-E monomeric, α-heavy chain (αHC) open conformers (OCs). Two mAbs (TFL-006 and TFL-007) were bound to the αHC's coated on a solid matrix. The binding was inhibited by the peptide 117AYDGKDY123, present in all alleles of the six HLA-I isoforms but masked by β2-microglobulin (β2-m) in intact HLA-I trimers (closed conformers, CCs). IVIg preparations administered to lower anti-HLA Abs in pre-and post-transplant patients have also shown HLA-I polyreactivity. We hypothesized that the mAbs that mimic IVIg HLA-I polyreactivity might also possess the immunomodulatory capabilities of IVIg. We tested the relative binding affinities of the mAbs and IVIg for both OCs and CCs and compared their effects on (a) the phytohemagglutinin (PHA)-activation T-cells; (b) the production of anti-HLA-II antibody (Ab) by B-memory cells and anti-HLA-I Ab by immortalized B-cells; and (c) the upregulation of CD4+, CD25+, and Fox P3+ T-regs. The mAbs bound only to OC, whereas IVIg bound to both CC and OC. The mAbs suppressed blastogenesis and proliferation of PHA-activated T-cells and anti-HLA Ab production by B-cells and expanded T-regs better than IVIg. We conclude that a humanized version of the TFL-mAbs could be an ideal, therapeutic IVIg-mimetic.
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Affiliation(s)
- Mepur H. Ravindranath
- Department of Hematology and Oncology, Children’s Hospital, Los Angeles, CA 90027, USA
- Emeritus Research Scientist at Terasaki Foundation Laboratory, Santa Monica, CA 90064, USA
| | | | - Edward J. Filippone
- Division of Nephrology, Department of Medicine, Sidney Kimmel Medical College at Thomas Jefferson Univsity, Philadelphia, PA 19145, USA;
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Bobrovnik SA, Ogloblya OV, Demchenko MO, Komisarenko SV. Kinetics of interaction between polyreactive immunoglobulins and antigen. UKRAINIAN BIOCHEMICAL JOURNAL 2020. [DOI: 10.15407/ubj92.05.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
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Evaluation of antiproliferative activity of pyrazolothiazolopyrimidine derivatives. UKRAINIAN BIOCHEMICAL JOURNAL 2018. [DOI: 10.15407/ubj90.02.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
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