title: Diagnosing XLP1 in patients with hemophagocytic lymphohistiocytosis.
abstract: BACKGROUND
  Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening, heterogeneous, hyperinflammmatory disorder. Prompt identification of inherited forms resulting from mutation in genes involved in cellular cytotoxicity can be crucial. X-linked lymphoproliferative disease 1 (XLP1), due to mutations in SH2D1A (Xq25) encoding signaling lymphocyte activation molecule-associated protein (SAP), may present with HLH. Defective SAP induces paradoxical inhibitory function of the 2B4 coreceptor and impaired natural killer (NK) (and T) cell response against EBV-infected cells.
  
  
  OBJECTIVE
  To characterize a cohort of patients with HLH and XLP1 for SAP expression and 2B4 function in lymphocytes, proposing a rapid diagnostic screening to direct mutation analysis.
  
  
  METHODS
  We set up rapid assays for 2B4 function (degranulation or (51)Cr-release) to be combined with intracellular SAP expression in peripheral blood NK cells. We studied 12 patients with confirmed mutation in SH2D1A and some family members.
  
  
  RESULTS
  The combined phenotypic/functional assays allowed efficient and complete diagnostic evaluation of all patients with XLP1, thus directing mutation analysis and treatment. Nine cases were SAP(-), 2 expressed SAP with mean relative fluorescence intensity values below the range of healthy controls (SAP(dull)), and 1, carrying the R55L mutation, was SAP(+). NK cells from all patients showed inhibitory 2B4 function and defective killing of B-EBV cells. Carriers with SH2D1A mutations abolishing SAP expression and low percentage of SAP(+) cells showed neutral 2B4 function at the polyclonal NK cell level. Three novel SH2D1A mutations have been identified.
  
  
  CONCLUSIONS
  Study of SAP expression is specific but may have insufficient sensitivity for screening XLP1 as a single tool. Combination with 2B4 functional assay allows identification of all cases.
authors.affiliation: Istituto di Ricovero e Cura a Carattere Scientifico Azienda Ospedaliera Universitaria San Martino-Istituto Nazionale per la Ricerca sul Cancro, Genoa, Italy.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Meazza
authors.affiliation: Istituto di Ricovero e Cura a Carattere Scientifico Azienda Ospedaliera Universitaria San Martino-Istituto Nazionale per la Ricerca sul Cancro, Genoa, Italy; Dipartimento di Medicina Sperimentale, Università degli Studi di Genova, Genoa, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Tuberosa
authors.affiliation: Dipartimento Oncoematologia Pediatrica, Azienda Ospedaliero-Universitaria Meyer, Florence, Italy; Pediatric Oncology Network, Istituto Toscano Tumori (I.T.T.), Florence, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Cetica
authors.affiliation: Istituto Giannina Gaslini, Genoa, Italy.
authors.forename: Michela
authors.initials: M
authors.lastname: Falco
authors.affiliation: Dipartimento di Medicina Molecolare e Traslazionale, Università degli Studi di Brescia, Brescia, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Parolini
authors.affiliation: Department of Medicine, Cambridge Institute for Medical Research, Cambridge, United Kingdom.
authors.forename: Sam
authors.initials: S
authors.lastname: Grieve
authors.affiliation: Department of Medicine, Cambridge Institute for Medical Research, Cambridge, United Kingdom.
authors.forename: Gillian M
authors.initials: GM
authors.lastname: Griffiths
authors.affiliation: Dipartimento Oncoematologia Pediatrica, Azienda Ospedaliero-Universitaria Meyer, Florence, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Sieni
authors.affiliation: Istituto Giannina Gaslini, Genoa, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Marcenaro
authors.affiliation: Istituto Giannina Gaslini, Genoa, Italy.
authors.forename: Concetta
authors.initials: C
authors.lastname: Micalizzi
authors.affiliation: Dipartimento di Scienze della Sanità Pubblica e Pediatriche, Università degli Studi di Torino, Turin, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Montin
authors.affiliation: Oncoematologia Pediatrica e Centro Trapianti, Ospedale Infantile Regina Margherita, Turin, Italy.
authors.forename: Franca
authors.initials: F
authors.lastname: Fagioli
authors.affiliation: Dipartimento di Medicina Sperimentale, Università degli Studi di Genova, Genoa, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Moretta
authors.affiliation: Istituto di Ricovero e Cura a Carattere Scientifico Azienda Ospedaliera Universitaria San Martino-Istituto Nazionale per la Ricerca sul Cancro, Genoa, Italy; Dipartimento di Medicina Sperimentale, Università degli Studi di Genova, Genoa, Italy.
authors.forename: Maria C
authors.initials: MC
authors.lastname: Mingari
authors.affiliation: Istituto Giannina Gaslini, Genoa, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Moretta
authors.affiliation: Division of Immunology, Boston Children's Hospital, Boston, Mass.
authors.forename: Luigi D
authors.initials: LD
authors.lastname: Notarangelo
authors.affiliation: Dipartimento di Medicina Sperimentale, Università degli Studi di Genova, Genoa, Italy; Istituto Giannina Gaslini, Genoa, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Bottino
authors.affiliation: Dipartimento Oncoematologia Pediatrica, Azienda Ospedaliero-Universitaria Meyer, Florence, Italy; Pediatric Oncology Network, Istituto Toscano Tumori (I.T.T.), Florence, Italy. Electronic address: maurizio.arico@ittumori.it.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Aricò
authors.affiliation: Istituto di Ricovero e Cura a Carattere Scientifico Azienda Ospedaliera Universitaria San Martino-Istituto Nazionale per la Ricerca sul Cancro, Genoa, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Pende
mesh_terms: D000293:Adolescent; D000328:Adult; D015703:Antigens, CD / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000276:immunology*; D007694:Killer Cells, Natural / Q000276:immunology; D007963:Leukocytes, Mononuclear / Q000276:immunology; D051359:Lymphohistiocytosis, Hemophagocytic / Q000175:diagnosis* / Q000235:genetics / Q000276:immunology; D008232:Lymphoproliferative Disorders / Q000175:diagnosis* / Q000235:genetics / Q000276:immunology; D008297:Male; D009154:Mutation; D011971:Receptors, Immunologic / Q000276:immunology*; D000071179:Signaling Lymphocytic Activation Molecule Associated Protein; D000071176:Signaling Lymphocytic Activation Molecule Family; D055815:Young Adult
chemical_list: D015703:Antigens, CD; C084093:CD244 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D011971:Receptors, Immunologic; C114953:SH2D1A protein, human; D000071179:Signaling Lymphocytic Activation Molecule Associated Protein; D000071176:Signaling Lymphocytic Activation Molecule Family
keywords: 2B4 function; HLH; NK cells; SAP expression; XLP1