Primary Immune Regulatory Disorders With an Autoimmune Lymphoproliferative Syndrome-Like Phenotype: Immunologic Evaluation, Early Diagnosis and Management

Abstract

Primary immune regulatory disorders (PIRD) are associated with autoimmunity, autoinflammation and/or dysregulation of lymphocyte homeostasis. Autoimmune lymphoproliferative syndrome (ALPS) is a PIRD due to an apoptotic defect in Fas-FasL pathway and characterized by benign and chronic lymphoproliferation, autoimmunity and increased risk of lymphoma. Clinical manifestations and typical laboratory biomarkers of ALPS have also been found in patients with a gene defect out of the Fas-FasL pathway (ALPS-like disorders). Following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA), we identified more than 600 patients suffering from 24 distinct genetic defects described in the literature with an autoimmune lymphoproliferative phenotype (ALPS-like syndromes) corresponding to phenocopies of primary immunodeficiency (PID) (NRAS, KRAS), susceptibility to EBV (MAGT1, PRKCD, XIAP, SH2D1A, RASGRP1, TNFRSF9), antibody deficiency (PIK3CD gain of function (GOF), PIK3R1 loss of function (LOF), CARD11 GOF), regulatory T-cells defects (CTLA4, LRBA, STAT3 GOF, IL2RA, IL2RB, DEF6), combined immunodeficiencies (ITK, STK4), defects in intrinsic and innate immunity and predisposition to infection (STAT1 GOF, IL12RB1) and autoimmunity/autoinflammation (ADA2, TNFAIP3,TPP2, TET2). CTLA4 and LRBA patients correspond around to 50% of total ALPS-like cases. However, only 100% of CTLA4, PRKCD, TET2 and NRAS/KRAS reported patients had an ALPS-like presentation, while the autoimmunity and lymphoproliferation combination resulted rare in other genetic defects. Recurrent infections, skin lesions, enteropathy and malignancy are the most common clinical manifestations. Some approaches available for the immunological study and identification of ALPS-like patients through flow cytometry and ALPS biomarkers are provided in this work. Protein expression assays for NKG2D, XIAP, SAP, CTLA4 and LRBA deficiencies and functional studies of AKT, STAT1 and STAT3 phosphorylation, are showed as useful tests. Patients suspected to suffer from one of these disorders require rapid and correct diagnosis allowing initiation of tailored specific therapeutic strategies and monitoring thereby improving the prognosis and their quality of life.

Keywords: ALPS; ALPS-like; autoimmunity; immune dysregulation; lymphoproliferation; malignancy.

Figure 1

ALPS-like related cases. Twenty-four distinct genetic defects with immune dysregulation, lymphoproliferation and autoimmunity were identified in the literature until October 2020. More than 2000 total cases were reported. After filtering according to the ALPS-like inclusion criteria, 645 patients were selected. (A) percentage of patients that fulfill clinical ALPS-like phenotype criteria. The number of ALPS-like patients with respect to the total number of patients counted in each genetic defect is indicated in parentheses. (B) ALPS-like related genes prevalence. *ALPS-like related genes with a prevalence less than 1%: PRKCD (0.9%), DEF6 (0.9%), RASGRP1 (0.8%), IL2RA (0.6%), IL2RB (0.6%), TNFRSF9 (0.5%), TET2 (0.5%), TPP2 (0.3%).

Figure 2

Clinical features associated with ALPS-like disorders. Blue: ALPS-like related genes with EBV-susceptibility; orange: ALPS-like related genes with regulatory T-cells defect; green: other ALPS-like related genes.

Figure 3

DNT in ALPS-like patients. (A) percentage of patients with normal (red bars) increased (blue bars) or not reported (gray bars) values of DNT. (B) range of DNT percentage presented in patients with high DNT. Circles: percentage of DNT in CD3+TCRαβ+ lymphocytes. Rhombus: percentage of DNT in CD3+ lymphocytes. Dashed line at point 3.8: DNT cutoff in CD3+TCRαβ+ lymphocytes. Dashed line at point 2.5: DNT cutoff in CD3+lymphocytes.

Figure 4

Pathophysiology and functional assays through flow cytometry in ALPS-like patients with EBV-susceptibility. (A) Schematic representation of the genetic defects (in color) and pathways identified in ALPS-like patients predisposing to high susceptibility to Epstein-Barr Virus (EBV)-driven lymphoproliferative disease. Immunologic studies are outlined in blue. The letters in parentheses refer to the functional studies included in figure 4. Defects in the control of EBV infection is mainly due to impairment of CD8, NK and NKT cell cytotoxicity (due to SAP, MAGT1 and TNFRSF9 deficiencies) and/or EBV-specific T cell proliferation (due to ITK, RASGRP1, TNFRSF9 deficiencies, PIK3CD gain of function and PIK3R1 loss of function) or survival (due to XIAP and STK4 deficiencies). (B) Decreased but not absent SAP expression in NK-cells of a patient with SAP deficiency. MFI: median fluorescence Intensity. (C) Decreased but not absent XIAP expression in NK-cells of a patient with XIAP deficiency. (D) Decreased NKG2D expression both in CD8 T and NK-cells of a MAGT1 patient (blue) in comparison with a healthy control (purple). (E) Hyperactivation of the PI3K-AKT signaling pathway is shown as high levels of AKT phosphorylation in a patient with PIK3R1 defect. (F) Senescence phenotype of CD8+CD57+ T-cells in a PIK3R1 patient. (G) Decreased CD3+Vα24+Vβ11+ invariant NKT-cells in a patient with common variable immunodeficiency and ALPS-like features.

Figure 5

Pathophysiology and functional assays through flow cytometry in ALPS-like patients with regulatory T-cells defect. (A) Schematic representation of the genetic defects (in color) and pathways identified in ALPS-like patients with Treg defect. Immunologic studies are outlined in orange. The letters in parentheses refer to the functional studies included in Figure 5. Altered Tregs levels and/or function is shown in patients with CTLA4, LRBA, DEF6, IL2RA and IL2RB deficiencies and gain of function of STAT3. (B) Decreased CD4+CD25+FoxP3+ Treg cells in a LRBA patient. (C) Lower CTLA4 levels in a patient with CTLA4 haploinsufficiency (blue) in comparison with the healthy control analyzed (purple). (D) Decreased LRBA expression in CD4 T-cells of a patient with LRBA deficiency (blue) in comparison with the healthy control analyzed (purple). (E) Expansion of CD4+CXCR5+CD45RA- circulant follicular helper T cells (cTFH) and polarization to CCR6-CXCR3+ Th1 phenotype in a LRBA patient. (F) Hyperphosphorylation and delayed dephosphorylation of STAT3 (in tyrosine 705) induced by IL-6 in a patient with gain of function of STAT3 in comparison of the healthy control included. Line graph shows the median intensity fluorescence of STAT3 phosphorylated in the STAT3 GOF patient (blue) and the healthy control (purple). NS, no stimulation.

Figure 6

Pathophysiology and functional assays in other ALPS-like related genes. Immunologic studies are outlined in green. It is shown schematic representation of the genetic defects and pathways identified in ALPS-like patients with RALD, TTP2 and TET2 disorders (A), IL12RB1, STAT1 GOF, TNFAIP3, CARD11 GOF (B), ADA2 (C). (D) Hyperphosphorylation and delayed dephosphorylation of STAT1 (in tyrosine 701) induced by IFNγ in patient´s monocytes with gain of function of STAT1 in comparison of the healthy control included. Line graph shows the MFI of STAT1 phosphorylated in the STAT1 GOF patient (blue) and the healthy control (purple). NS, no stimulation.

Figure 7

Monitorization of two cases of STAT3 GOF and LRBA deficiency measuring sCD25. Arrows indicate the changes in the treatment. HCQ, hydroxychloroquine; MMF, mycophenolate mofetil; SCIg, subcutaneous immunoglobulin therapy.