Defects of Innate Immunity

Defects of Innate Immunity

TLR signalling

IRAK4 and MyD88 AR Same clinical phenotype for both genes (Recurrent) invasive bacterial infections: Meningitis and septicemia >> skin Pneumococcus >> Staph aureus > Pseudomonas 40% of cases die of invasive bacterial infection Usually <2yo (no infections >8yo) Poor inflammatory response (fever, CRP)

TLR signalling

IRAK4 and MyD88 Test available: CD62L shedding (Tuesdays) Management: Immunisation Prophylactic antibiotics

Anhidrotic ectodermal dysplasia NEMO (XL) or IKBA (AD) gain of function Viral AND bacterial (pneumococcus) AND fungal (Candida) AND atypical mycobacteria Sepsis, gut infection, pneumonia Sparse hair, sparse conical teeth, cannot sweat (ectodysplasin receptor)

TLR signalling

Anhidrotic ectodermal dysplasia Tests: Clinical plus... Standard investigations of T and B cells Treatment depends on the level of ID Immunisations Prophylactic antibiotics IVIG HSCT

Candida CARD9 STAT1 gain of function IL17R IL17 (HIES: absent Th17 cells) (APECED: IL17 autoantibodies) (Combined IDs)

Defects associated with CMC

HPV WHIM Warts, Hypogammaglobulinemia (and low B cells), ID and Myelokathexis (and neutropenia) CXCL4 (chemokine receptor) gain of function Ligand widely expressed EVER Warts only On lymphocytes and keratinocytes (Combined IDs e.g. DOCK8, GATA2, STK4)

Defects associated with HPV

HSV Encephalitis CNS: neurons, astrocytes, oligodendrocytes Multiple genes: TLR3 (AD, AR) UNC93B (AR) TRAF3 (AD) TRIF (AD, AR) TBK1 (AD) HSV encephalitis only

Genetic susceptibility to HSE

Immune Dysregulation

Familial HLH Decreased or absent cytotoxicity WithOUT hypopigmentation Perforin (PRF1, FHL2) UNC13D (FHL3) STX11 (FHL4) STXBP2 (FHL5) With hypopigmentation (partial albinism) Chediak Higashi (LYST) Griscelli (RAB27)

HLH Primary HLH Secondary HLH Systemic autoimmune disease Malignancy Infection??

Diagnostic criteria for HLH A. Molecular diagnosis consistent with HLH: pathogenic mutations of PRF1, UNC13D, STXBP2, STX11, Rab27a, LYST, SH2D1A or XIAP B. Five of the eight criteria listed below are fulfilled 1. Fever 38.5 C 2. Splenomegaly 3. Cytopaenias (affecting at least 2 of 3 lineages in peripheral blood) Hb <90g/L (in infants <4 weeks: Hb<100g/L) Platelets <100 x 10 9 /L Neutrophils <1 x 10 9 /L 4. Hypertriglyceridemia (fasting 3mmol/L) and/or hypofibrinogemia ( 1.5g/L) 5. Ferritin 500μg/L 6. Elevated scd25 (α-chain of sil-2 receptor) 7. Haemophagocytosis in bone marrow, spleen, lymph nodes or liver 8. Low or absent NK cell activity Henter J et al. Pediatr Blood Cancer 2007;48:124 131

Diagnostic criteria for HLH A. Molecular diagnosis consistent with HLH: pathogenic mutations of PRF1, UNC13D, STXBP2, STX11, Rab27a, LYST, SH2D1A or XIAP B. Five of the eight criteria listed below are fulfilled 1. Fever 38.5 C 2. Splenomegaly 3. Cytopaenias (affecting at least 2 of 3 lineages in peripheral blood) Hb <90g/L (in infants <4 weeks: Hb<100g/L) Platelets <100 x 10 9 /L Neutrophils <1 x 10 9 /L 4. Hypertriglyceridemia (fasting 3mmol/L) and/or hypofibrinogemia ( 1.5g/L) 5. Ferritin 500μg/L 6. Elevated scd25 (α-chain of sil-2 receptor) 7. Haemophagocytosis in bone marrow, spleen, lymph nodes or liver 8. Low or absent NK cell activity

Ferritin and scd25 (IL2Rα) Ferritin 500μg/L in HLH-04 criteria Recent studies >10 000μg/L highly sensitive (90%) and specific (96%) for HLH Rate of decline of ferritin may be useful prognostic marker Lin T et al. Pediatr Blood Cancer 2011;56:154-155 Allen C et al. Pediatr Blood Cancer 2008;50:1227-1235

Ferritin and scd25 (IL2Rα) Interleukin-2 receptor-α Upregulated on activated T cells Elevated in inflammation High levels in HLH Normal ranges for levels of scd25 vary with age Method dependent Komp DM et al Blood.1989 73: 2128-2132

Diagnostic criteria for HLH A. Molecular diagnosis consistent with HLH: pathogenic mutations of PRF1, UNC13D, STXBP2, STX11, Rab27a, LYST, SH2D1A or XIAP B. Five of the eight criteria listed below are fulfilled 1. Fever 38.5 C 2. Splenomegaly 3. Cytopaenias (affecting at least 2 of 3 lineages in peripheral blood) Hb <90g/L (in infants <4 weeks: Hb<100g/L) Platelets <100 x 10 9 /L Neutrophils <1 x 10 9 /L 4. Hypertriglyceridemia (fasting 3mmol/L) and/or hypofibrinogemia ( 1.5g/L) 5. Ferritin 500μg/L 6. Elevated scd25 (α-chain of sil-2 receptor) 7. Haemophagocytosis in bone marrow, spleen, lymph nodes or liver 8. Low or absent NK cell activity

Haemophagocytosis Lacks sensitivity and specificity for HLH May not be present early in disease Marked heterogeneity in BM involvement in both primary HLH and secondary forms of HLH Used in combination with other diagnostic features Gupta A et al. Pediatr Blood Cancer 2008;50:192-194

Diagnostic criteria for HLH A. Molecular diagnosis consistent with HLH: pathogenic mutations of PRF1, UNC13D, STXBP2, STX11, Rab27a, LYST, SH2D1A or XIAP B. Five of the eight criteria listed below are fulfilled 1. Fever 38.5 C 2. Splenomegaly 3. Cytopaenias (affecting at least 2 of 3 lineages in peripheral blood) Hb <90g/L (in infants <4 weeks: Hb<100g/L) Platelets <100 x 10 9 /L Neutrophils <1 x 10 9 /L 4. Hypertriglyceridemia (fasting 3mmol/L) and/or hypofibrinogemia ( 1.5g/L) 5. Ferritin 500μg/L 6. Elevated scd25 (α-chain of sil-2 receptor) 7. Haemophagocytosis in bone marrow, spleen, lymph nodes or liver 8. Low or absent NK cell activity

NK cell function Jordan B et al. Blood 2011;118:4041-4052

NK cell function assays NK cell cytotoxicity Intracellular perforin expression CD107a expression (degranulation)

Diagnostic algorithm HLH diagnosed or suspected Male Female (NK cell cytotoxicity) CD107a expression Perforin expression SAP protein expression + XIAP protein expression (NK cell cytotoxicity) CD107a expression Perforin expression

HLH: a disease of risk factors? Primary HLH Secondary HLH?

Lymphoproliferation without Autoimmunity XLP1 Predisposition to EBV-associated LPD and HLH SAP deficiency (SH2D1A, XL) Hypogammaglobulinemia XLP2 XIAP deficiency (BIRC4 mutation, XL) Colitis/IBD, LPD (+/- LPD) ITK (AR) and CD27 (AR) Predisposition to EBV-associated LPD

Autoimmune Lymphoproliferation (ALPS) Three gene defects FAS (AD) FAS (somatic, DNTs) FAS ligand (AR) Caspase 10 (AR) Splenomegaly Lymphadenopathy Autoimmunity: cytopenias

Autoimmune Lymphoproliferation (ALPS) Investigations: Double negative T cells (TCRab+) Defective apoptosis Management: Treat the cytopenias (steroids, AZA, MMF, sirolimus)?hsct

Autoimmunity without Lymphoproliferation IPEX syndrome: Immunodysregulation, Polyendocrinopathy, Enteropathy, XL Autoimmune enteropathy, early onset diabetes, cytopenias, eczema FOXP3 mutation (XL) Defect of Tregs (CD4+/CD25+FOXP3+)

Autoimmunity without Lymphoproliferation APECED (APS1): Autoimmune polyendocrinopathy (hypothyroidism, hypoparathyroidism, adrenal insufficiency), candidiasis, ectodermal dysplasia (alopecia) AIRE mutation (AR) Autoreactive T cells in thymus not deleted

Dysregulation with Colitis Genes: IL10 (AR) IL10R (AR) Severe early onset IBD Recurrent respiratory infection Arthritis HSCT...