Conclusions: Chronic use of high dose GCs is a relatively common med-ical situation frequently associated with T cell lymphophenia and in-creased susceptibility to opportunistic infections. By studying ECS-Pre and ECS-Post patients we were able to describe the bona-fide effect of GCs on the immune system in general, and T lymphocytes in particular. Decreased lymphocyte/thymic output, as well as increased apoptotic T-cell death underlies lymphopenia in ECS/chronic GCs-exposed patients. Under such conditions, IL-21 was significantly decreased in plasma and our in-vitro studies showed that IL-21 replenishment was able to increase BCL2 (anti-apoptotic molecule) and BCL6 expression, and efficiently counteract the apoptotic effects of GCs. Recombinant IL-21 has been explored as a co-adjuvant treatment for multiple human cancers and may offer a treatment option for lymphopenia and its complications in patients with ECS/ chronic GCs exposure. Further studies are warranted to evaluate this therapeutic option.
(251) Submission ID#619776
F-BAR domain only protein 1 (FCHO1) deficiency is a novel cause of combined immune deficiency in humans
Enrica Calzoni, MD1, Craig D. Platt, MD, PhD2, Sevgi Keles, MD3, Hye Sun Kuehn, PhD4, Yu Zhang, PhD5, Julia Pazmandi, MSc6, Gaetana Lanzi, PhD7, Azzedine Tahiat, PhD8, Hasibe Artac, MD9, Jasmin Dmytrus, Msc10, Ismail Reisli, MD11, Dilara Uygun, MD12, Bertrand Boisson, PhD13, Sergio D. Rosenzweig, MD/PhD14, Helen C. Su, MD, PhD15, Silvia Giliani, PhD16, Michael J. Lenardo, MD17, Raif S. Geha,
MD18, Kaan Boztug, MD19, Janet Chou, MD20, Luigi D. Notarangelo,
MD, PhD21
1Graduate Student, Laboratory of Clinical Immunology and
Microbiology, IDGS, DIR, NIAID, NIH, Bethesda, MD, USA
2
Attending Physician, Division of Immunology, Boston Childrens Hospital, Harvard Medical School, Boston, MA 02115
3
Attending Physician, Division of Pediatric Immunology and Allergy, Meram Medical Faculty, Necmettin Erbakan University, Konya, Turkey
4
Staff Scientist, Immunology Service, Department of Laboratory Medicine, Clinical Center, NIH, USA
5
Staff Scientist, Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
6
Graduate Student, Ludwig Boltzmann Institute for Rare and Undiagnosed Diseases, Vienna, Austria
7Staff Scientist, A. Nocicelli Institute for Molecular Medicine,
Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
8Staff Scientist, Laboratory of Medical Biology, Rouiba Hospital,
Algiers, Algeria
9
Attending Physician, Pediatric Immunology and Allergy, Selcuk University Medical Faculty, Konya, Turkey
10
Graduate Student, Ludwig Boltzmann Institute for Rare and Undiagnosed Diseases, Vienna, Austria
11
Professor, Division of Pediatric Immunology and Allergy, Meram Medical Faculty, Necmettin Erbakan University, Konya, Turkey
12
Attending Physician, Department of Immunology-Allergy, Akdeniz University School of Medicine, Antalya, Turkey
13
Assistant Professor, St. Giles Laboratory of Human Genetics of Infectious Diseases, Rockefeller Branch, The Rockefeller University, New York, NY 10065
14
Chief, Immunology Service, Department of Laboratory Medicine, NIH Clinical Center, Bethesda, MD, USA
15
Chief, Human Immunological Diseases Section, Laboratory of Clinical Immunology and Microbiology, NIAID, NIH, Bethesda, MD
16
Associate Professor, A. Nocicelli Institute for Molecular Medicine, Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
17
Senior Investigator, Molecular Development of the Immune System Section, Laboratory of Immune System Biology, NIAID, National Institutes of Health, Bethesda, MD, USA
18
Chief, Division of Immunology, Boston Childrens Hospital, Harvard Medical School, Boston, MA 02115
19Director, Ludwig Boltzmann Institute for Rare and Undiagnosed
Diseases, Vienna, Austria
20Associate Professor, Division of Immunology, Boston Childrens
Hospital, Harvard Medical School, Boston, MA 02115
21
Chief, Laboratory of Clinical Immunology and Microbiology, IDGS, DIR, NIAID, NIH, Bethesda, MD, USA
Abstract
Clathrin-mediated endocytosis (CME) is the major endocytic pathway by which eukaryotic cells internalize cell-surface cargo proteins and extra-cellular molecules, thereby allowing for a broad range of biological pro-cesses, including cell signaling, nutrient and growth factor uptake, and cell fate and differentiation1. The FBAR domain only proteins 1 and 2 (FCHO1/FCHO2) are involved in the initiation of clathrin coat pit for-mation. Whether FCHO1 and FCHO2 are functionally redundant or have distinct functions is unclear. We report here the first cases of a severe immunodeficiency due to a genetic defect affecting CME. By using whole exome sequencing and genomic analysis of a targeted PID gene panel, we have identified biallelic loss-of-function FCHO1 mutations in five patients from unrelated families of Italian (P1), Turkish (P2, P3, and P5) and Algerian (P4) origin with severe T cell lymphopenia manifesting as recurrent and severe infections of bacterial, mycobacterial, viral and fungal origin. P3 developed EBV-associated diffuse large B cell lympho-ma. Three patients (P3-P5) died in childhood, whereas P1 and P2 are alive with full donor chimerism at 13 and 1.5 years after allogeneic hemato-poietic stem cell transplantation, respectively and have cleared pre-trans-plant infections. Patients P2, P3, and P4 carried homozygous frameshift mutations predicted to cause premature termination. Western-blotting analysis of HA- or FLAG-tagged FCHO1 constructs showed expression of truncated products in P2 and P3, whereas no protein was detected in P4, presumably due to mRNA decay. P1 and P5 carried homozygous splice-site mutations at the invariant -1 and +1 positions, respectively, leading to skipping of exon 6 in P1's FCHO1 cDNA. qPCR analysis demonstrated differential expression of the FCHO1 and FCHO2 genes, with the former being predominantly expressed in lymphoid cells, where-as FCHO2 wwhere-as more abundantly expressed in fibroblwhere-asts and K562 cells. Analysis of T cell activation in P2 (the only patient for whom pre-trans-plant PBMC were available) revealed reduced T cell proliferation. While TCR internalization in response to CD3 cross-linking was normal (con-sistent with recent evidence that TCR internalization occurs through a clathrin-independent pathway), chase experiments demonstrated that transferrin internalization was abolished in activated T cells from P2. We had previously reported that a missense mutation in TFRC, encoding transferrin receptor 1, impairs transferrin internalization and intracellular iron delivery, causing a combined immunodeficiency with defective T cell proliferation.
Our data identify the first form of severe immunodeficiency due to defects of clathrin-mediated endocytosis, and provide additional evidence in sup-port of the critical role played by iron cellular metabolism in T cell func-tion and homeostasis.
J Clin Immunol (2019) 39 (Suppl 1):S1–S151 S150
Publisher’s Note Springer Nature remains neutral with regard to juris-dictional claims in published maps and institutional affiliations.
