Primary Immunodeficiencies

• Heterogenous group of rare, single-gene diseases leading to impairment of the immune responses

• Inherited as X-linked or autosomal disorders, either dominant or recessive

• gene defects lead to missing enzymes, developmental arrest in immune differentiation, absent or non-functional proteins, abnormal DNA repair, altered signal transduction, impairment of cell-to-cell and intracellular communications

• Incidence, Prevalence• ranges from 1:300 (sIgA deficiency) to 1:100 000

live births (SCID)• 80% of affected persons < 20 years of age• 70% males (5:1 males in children; 1:1 in adults)• over 120 different entities described; of them,

about 20 account for > 90% of cases

• increasing due to better methodologies and newborn screening programs (2000s: 1 / 10 000 European Society for Immunodeficiencies EDIS Registry)

0

10

20

30

40

50

60

%

Humoral

Cellular

Combined

Phagocytic

Complement

others

Suspected when:• - two or more episodes of consolidative pneumonia in one

year

• two or more serious sinus infections in one year

• recurrent deep skin or organ abscesses

• two or more deep-seated infections such as meningitis, sepsis, osteomyelitis, cellulitis

• iv antibiotics required to clear up infections

• little effect of antibiotics

• persistent oral or skin thrush after age of 1

• Pneumocystis carinii, Aspergillus infections

• Positive family history

• Organ complications from infections (bronchiectasis, chronic sinusitis, mastoiditis, CNS involvement)

• Chronic diarrhea, malabsorbtion due to recurrent giardiasis, rotaviruses, cryptosopidiosis

• Chronic GI inflammatory diseases (IBD, gluten enteropathy, atrophic gastritis with pernicious anemia, nodular lymphoid hyperplasia)

• Autoimmune disorders (autoimmune hemolytic anemia, thrombocytopenia, leukopenia, SLE)

• Other causes carefully evaluated and excluded:• allergic rhinitis, nasal structural abnormalities

(polyps, deviated septum, chronic hyperplastic rhinitis_

• adenoidal hypertrophy• cystic fibrosis, ciliary diskinesia, COPD,

bronchiectasis• immunosupresive therapy, malnutrition,

infiltrative diseases, malignancies, infectious diseases, protein losing disorders

• (Atkinson, 2007)

Human Primary Immunodeficiency DiseasesAlain Fischer, Immunity 27, December 2007

Cellular and Genetic Basis of PrimaryImmune DeficienciesJames W. Verbsky, MD, PhDa,William J. Grossman, MD, PhDPediatr Clin N Am 53 (2006) 649–684

General categories of PIDs (Saunders & Mak, 2006)

• SCID - low numbers/absence of T cells and sometimes of B cells; lack of B cell functions due to T cell function impairment

• T-PIDs - normal numbers of T, B, NK cells; T cells are non-functional; B cell function may be affected

• B-PIDs - B cells non-functional or absent; T and NK cells are normal

• DNA repair defects - low lymphocyte numbers

• Lymphoproliferative disorders - mutations in death receptors or ligands, or in caspase cascade; uncontrolled proliferation of T and B cells

• Phagocyte response deficiencies - defects in extravasation, activation, function of phagocytes

• IL-12 / IFN gamma axis - failure in macrophage (hyper-)activation

• Autoinflammatory syndromes - severe local inflammation and prolonged periodic fevers with no obvious cause; lymphocyte numbers are normal

• Neutropenias - reduced level of neutrophils in circulation

• Complement deficiencies - lack of complement activation; T and B cells are normal

Laboratory Diagnosis

- flowcytometry for lymphocyte lineage enumeration

- biochemical tests for soluble molecule

- cellular (functional) tests

- genetic tests

Treatment of PIDs (immunological)

- Intravenous immunoglobulin replacement therapy, established in the 1980s to threat hypoglobulinemia. The IV-IG preparation most often used: 10% IgG in a form that resists aggregation and has low risk of complement activation; 400-600mg/kg/month is usually sufficient to prevent recurrent infections. Risk of IgE-anti-IgA anaphylaxy (in serum/secreted IgA-deficient patients). Not indicated if hypogammaglobulinemia is secondary of protein-loss conditions (congenital lymphangiectasia, enteropathies) or in transient hypoglobulinemia of infancy / steroid induced hypogammaglobulinemia.

- Enzyme replacement: PEGADA (Polyethylene glycol-treated bovine adenosine deaminase) in infants with ADA-deficient SCID if bone marrow transplantation has already failed.

- Bone Marrow (BMT) / Hematopoietic cell transplantation (HCT) from histocompatible (/half compatible) donors; prenatal diagnosis allows for in utero transplantation; ~ 60% survival rate (risk of the GvHD <= controlled by Cyclosporine, Methothrexate, steroids); some may require long term IV-IG

-Thymus transplantation (DiGiorge), from related siblings (either fetal thymus transplantation, bone marrow cells including residual adult T cells, or cultured HLA-DR-matched cultured mature thymic epithelial explants)

- gene therapy - still a main topic in research (positive hints for SCID-X1 retroviral-mediated gene transfer; ADA mutation; of the 20 patients in a French cohort: 3 developed leukemia apparently associated with LMO2 - locus integration.)

Disorders of Immune regulation

Genetics of PIDs - X chromosome

Selective IgA deficiency

- 1:333 blood donors

- reported in both apparently healthy and patients

- infections of the respiratory, gastrointestinal, urogenital tracts

- frequent occurrence of autoimmune diseases and increased incidence of malignacy

- serum IgA < 10mg/dL (! Cross-reactivity of IgG against cow milk and ruminant serum proteins => false detection of IgA when using goat, but not rabbit, antisera)

~ 40% have anti-IgA antibodies (including IgE; risk of severe anaphylactic reactions; only washed erythrocytes can be administered in case of blood transfusions)

- cause unknown

- heterogeneic condition; some patients: genetic linkage to MHC III (HLA-DR3, -B8, -A1 in Northern Europeans); in others, it develops secondary to dilantin, sulfasalazine, d-penicillamine, gold therapy); in vitro: some patients may show B lymphocytes able to switch to IgA under anti-CD40 and IL-10

Selective IgG deficiency

- recurrent upper and lower respiratory tract infections (autosomal recessive; defect unknown but mutations were reported of the Igh locus: gamma3, gamma2

-associate allergy, autoimmunity, malignancies

- IV-IG

Anti-polysaccharide deficiency (APAD)

- revealed often by vaccination (pneumococci and meningococci)

- IV-IG

Hyper IgE Syndrome

- extremely high levels of IgE; often also IgD

- characteristic facies in children; dermatitis and pyogenic infections (staphylococci affecting lungs, joints, skin: Job’s syndrome, after the Biblical sufferer). Respiratory allergies are rare, and the dermatitis is quite distinct from that of the atopic form. Associate abnormalities in tooh root resorbtion (not loosing the primary teeth). Reduced bone density (fractures). Very rare autoimmunity and malignancies.

- elevated numbers of eosinophils in blood and sputum; some impairments in secondary humoral responses, chemotaxis of neutrophils.

- some forms are autosomal dominant

- some associate defects in IgE catabolism

- some have low propensity in IFN gamma production by Th, but not increased IL-4; possible mutations in the IL-4Ralpha receptor chain (common for IL-4 and IL-13) resulting in increased signaling

- Antibiotics; surgery; no effect for IFNgamma or BMT/HCT

Hyper-IgE syndrome. Also known as Job syndrome, this immunodeficiency has a distinct facial expression with mild asymmetry, prominent jaw, and wide nasal ala. Eczematous skin lesions, recurrent staphylococcal skin infections, recurrent episodes of pneumonias often due to Staphylococcus aureus, pneumatoceles, and mucocutaneous candidiasis are common. Delayed shedding of primary teeth and skeletal abnormalities including severe scoliosis and recurrent pathologic fractures further characterize these patients. The morbidity of this disease varies, and some patients survive into adulthood, as did the patient pictured here. Written permission of the patient was obtained for use of this picture for medical publication through the courtesy of Dr Charlotte Cunningham-Rundles, Mount Sinai Medical Center, New York, NY, and the Immune Deficiency Foundation, Towson, Md. JACI 120-982, 2007

Hyper IgM Syndrome

-5 types; the most common is secondary to CD40L-deficiency affecting Th cells

-HIGM2: autosomally inherited mutations in AID: in contrast with HIGM1, no hypermutation detectable and different opportunistic infections (as CD40L is normal); abnormal giant CGs with many IgD and IgM harboring B lymphocytes, enlarged lymphoid organs.

-HIGM3: autosomal recessive mutations CD40; very similar to X-linked HIGM1, with deficits of cell mediated immunity

-HIGM4 - similar to, and milder than HIGM2, but impaired humoral immune responses (opportunistic bacterial and mycobacterial infections). Hypermutation is not affected. CD40, CD40L, AID, UNG, NEMO are normal, but defects downstream of CD40 signaling and DNA-repair prevent class switch

- HIGM5 - very similar to HIGM2, with susceptibility to bacterial (not opportunistic) infections. The defect lies in uracil DNA glycosilase UNG, that acts downstream of AID, removing the uracil residues deaminated by AID, removal that initiate the double-stranded breaks required for class switch.

- HIGM-NEMO (HIGM associated with X-linked hypohydrotic ectodermal dysplasia) is a mild form of HIGM; sparse hair and abnormal or missing teeth, lack swat glands. Impaired responses to polysaccharides, but also of cell-mediated immunity. Frequent opportunistic bacterial and mycobacterial infections. NEMO = NF-kappaB essential modulator, part of the IKK (IbB kinase) complex that phosphorylates IkB - the inhobitor of the NF-kB. That stands that NF-kB is involved in the CD40-indiced class switch, but details are still missing

CONGENITAL Agammaglobulinemia (Brunton XLA)

- rare (1:200 000); affects boys; lack of mature B cells and all isotypes; unusually suceptible to pyogenic bacterial infections. Over 300 distinct mutations invove the Btk, those continous signaling is required for differentiation from the preB stage. Myeloid cells appears normal, T cells are not affected. Within families, there were described different phenotypes. Mouse models reveals a less devastating picture than in humans.

Non Brunton-Agammaglobulinemia (NBA)

- accounts for ~10% of the patients with XLA-phonotype

-mutations in the miu heavy chain gene, lambda5, Igalpha, BLNK = > blocks in proB or preB cell transition (earlier than in Btk mutations).

- involved genes are autosomal, so both boys and girls are affected

CVID, Common Variable Immunodeficiencies / acquired hypogammaglobulinemia (~1:30 000)

-heterogenous group of disease, general impairment in humoral immune responses

- profound decrease in IgG, IgA, and ~50% also lack IgM. There are circulating, mature, B cells, but no memory B cells.

- recurrent bacterial infections starting in childhood similar with XLA, but ENLARGED lymphoid tissues (particularly Peyer’s patches). 1/4 die of chronic pulmonary disease or B cell lymphomas; amyloidosis, non-caseating granulomasta of the lung, splle, skin, liver and autoimmunity are common.

- IV-IG improves the clinical conditions; in some of them also IL-2

-reported defects: PKC activation pathway, DNA repair, protein tyrosine phosphorylation paths, upregulated Fas. Other appears to be seccondary to T cell defects

- mutations in MHC III (linked to TNF and LT).

~30%: low counts for Th cells; ~40%: decreased CD40L expression on Th)

- defects of the ICOS gene (inducible costimulator that contributed to T activation, GC formation, class switch): normal counts for T cells, but deficits of naïve and memory B cells

Lymphoprolipherative syndromes

XLP (X-linked lymphoprolipherative disorder)

-young boys: inappropriate response to the common EBV infection (leading to fulminant liver necrosis)

-uncontrolled proliferation of B cells, lymphadenopathy, hepatosplenomegaly, aplastic anemia, fever, associated with high serum levels for IFN gamma (Th1). Survivors may develop a selective Ig deficiency or Burkitt’s lymphoma; death occurs before age 50 years due to hepatic necrosis or bone marrow failure).

- only EBV triggers the disease

- the defect is in the SAP gene (SLAM-associated protein= SH2D1A = DSHP). SAP associated with SLAM (measles virus receptor) - molecule that is a minor costimulator for B, T cells, and is also expressed on DCs. SAP appears to downmodulate the IFNgamma production by T cells. If SAP is defective, Th are constimulated by a CD28-independent way. NK cells also use SAP; they fail to lyse EBV-infected B lymphocytes.

Lymphoprolipherative syndromes

ALPS (Autoimmune lymphoprolipherative syndromes)

- hyperproliferation of B cells (CD5+), Tc, and DN thymocytes, but not other subsets/types.

-enlargement of lymphoid organs (lymphadenopathy and hepatosplenomegaly) diagnosed usualy until age of 5.

-increased levels of IgG, IgA

-autoimmunity: anemia, thrombocytopenia; breat, colon, lung cancers and lymphomas

-defects in the Fas-mediated pathway

-ALPS Ia: mutations in CD95; ALPS Ib: defects in CD95L; ALPS II: mutations in caspase 10; unknown for ALPS III

-although the transmission is autosomal, the effect is genre-independent, as CD95 must function as a trimer (similar to the TRAPS)

DiGeorge syndrome

-complex disorder affecting thymus genesis (~1:4 000 live births)

-abnormal facies (long narrow face, small mouth, prominent nose, hooded or full upper eyelids, low-set cupped ears), small hands, abundant hair on the head, cardiac and renal malformations, cleft palate, neural tube defects, parahypothyroidism, recurrent infections.

-translocations or large (2Mbp) deletions 22q1, (sometimes associated with maternal alcoholism, diabetes, chemicals), and possible TBX1 mutation, a transcription factor involved also in aortal development, GSCL (goosecoid-like) - involved in neurogenesis, and HIRA, a corepressor involved in embryonic histone transcription in heart, cranium, pharyngeal arches.

-T cells, if present, display abnormal tendency to spontaneous apoptosis. NK and B counts appear normal

-murine equivalent: nude defect.DiGeorge syndrome. The characteristic facies of infantswith DiGeorge syndrome include widened epicanthal folds,flattened nasal bridge, short philtrum, recessed chin, roundedsmall mouth, and low set, posteriorly rotated ears with simplifiedhelices.

WAS Wiscott-Aldrich Syndrome

-X-linked recessive heterogenous disorder, WAS protein gene. WASP is expressed by all hematopoietic cells; is involved in HSC survival.

~1/3 patients (classic WAS) CID, eczema, thrombocytopenia; increased susceptibility to viral, pyogenic, opportunistic infecitons, autoimmunity, allergy, lymphomas)

~1/5 patients: only some of the above (Thrombocytopenia, XLT)

WASP is critical for both lymphocyte and platelet survival. DTH responses are affected; normal IgG but reduced IgM and elevated IgA and E levels.

- unclear mechanism; WASP binds to SH3-containing signaling molecules, Src kinases, Grb2 adaptor protein, PLC gamma, Btk, nut also with the cytoskeleton (acting as direct effector of the GTPase Cdc42, a regulator of the cytoskeleton organization). All these are important in T cell activation.

IV-IG, splenectomy, BMT/HCT

Wiskott-Aldrich syndrome (WAS). Recurrent bacterial,fungal, and, in this case, viral (Herpes simplex) infectionsplague patients with WAS. Equally a problem is that ofbleeding into eczematous skin lesions, mucosal surfaces,and other tissues because of concomitant thrombocytopeniaand small platelet size. The long-term prognosis is complicatedby an increased risk of malignancies and autoimmunedisorders. Patient died at age of 14.

Defects in DNA repair

-non-homologous end joining repair of DSB, homologous recombination repair, nucleotide excision repair (NHEJ, NER, NER)

AT, Ataxia-Telangiectasia

-autosomal recessive, progressive cerebellar ataxia, oculocutaneous telangiectasia, variable CID

recurrent severe lung infections, sins infections, hypo IgA, IgE, IgG2, IgG4; hypersensitive to ionizing radiation, increased risk of cancer (lymphomas, acute leukemias), autoimmunity.

Due to neurological defects, patients confined to weelchair before age 20, and die before 30. No effective treatment.

Defects: in ATM gene (ataxia telangiectasia mutated), that encodes a PI3K family protein that phosphorylated p53, thus preventing it’s interaction with Mdm2 and subsequent ubiquitin-directed degradation.

Ataxia telangiectasia (AT). This patient demonstratesfacial cellulitis and periorbital telangiectasias. The AT mutatedgene produces pleiotropic changes in cellular response toradiation, cell cycle control, and intracellular transport ofproteins that manifest themselves in choreoathetosis, cerebellarataxia, susceptibility to malignancies, and humoral andcellular (T-cell) deficiency. Patients with AT frequently havegreatly elevated serum levels of a-fetoprotein due to defectiveliver metabolism. Patient died at less than 10 years of age.

Nijmengen Breakage Syndrome (NHEJ defects)

Bloom syndrome

Xeroderma pigmentosum

T cell defects

-CD8 lymphocytopenia, or Zap70 deficiency

-p56lck defects

-HLA I defects

-HLA II defects

SCID. This patient typifies the wasted infant with SCIDwith failure to thrive and repeated infections. This patient hasno human leukocyte antigen/mixed leukocyte culture matchedsiblings and at the time (circa 1970s) was not a candidate for amismatched bone marrow transplant. This child succumbed tohis infections.