STAT5 proteins are components of the common growth hormone and interleukin 2 family of cytokines' signaling pathway. Mutations in the STAT5b gene, described in 2 patients, lead to growth hormone insensitivity that resembles Laron syndrome. Clinical immunodeficiency was also present, although immunologic defects have not been well characterized thus far. Here we describe a 16-year-old girl who suffered generalized eczema and recurrent infections of the skin and respiratory tract since birth. She also suffered severe chronic lung disease and multiple episodes of herpetic keratitis. Clinical features of congenital growth hormone deficiency were observed, such as persistently low growth rate, severely delayed bone age, and postnatal growth failure resulting from growth hormone resistance. This combined phenotype of growth hormone insensitivity and immunodeficiency was attributable to a homozygous C-->T transition that resulted in a nonsense mutation at codon 152 in exon 5 of the STAT5b gene. This novel mutation determined a complete absence of protein expression. The main immunologic findings were moderate T-cell lymphopenia (1274/mm3), normal CD4/CD8 ratio, and very low numbers of natural killer (18/mm3) and gammadelta T (5/mm3) cells. T cells presented a chronically hyperactivated phenotype. In vitro T-cell proliferation and interleukin 2 signaling were impaired. CD4+ and CD25+ regulatory T cells were significantly diminished, and they probably contributed to the signs of homeostatic mechanism deregulation found in this patient. This new case, in accordance with 2 previously reported cases, definitely demonstrates the significant role of the STAT5b protein in mediating growth hormone actions. Furthermore, the main immunologic findings bring about an explanation for the clinical immunodeficiency features and reveal for the first time the relevant role of STAT5b as a key protein for T-cell functions in humans.

HLA alleles are known to be associated with susceptibility to develop autoimmune hepatitis (AH), and hepatitis A virus (HAV) infection is postulated as a putative trigger for AH. We investigated whether HLA may influence the outcome of the HAV infection by studying 67 children with self-limited and 39 children with protracted forms of this infection. HLA typing of the uncomplicated forms showed no significant increase of any HLA class I or II alleles. In contrast, DRB1*1301 was present in 46.1% of the children with protracted forms (vs. 9.8% in healthy controls; relative risk [RR]: 7.6; 2 ‫؍‬ 33.3; P ‫؍‬ 2 ؋ 10 ؊9 ). In uncomplicated hepatitis, 45% developed anti-smooth muscle antibody (SMA)/actin antibodies, but only 1 child had detectable antibodies after 3 months of infection onset. In contrast, after 1 year, 69% of the patients suffering protracted forms had titers of anti-SMA/actin antibodies that ranged between 1:40 and 1:160. Within their follow-up, 2 patients developed a Hashimoto's thyroiditis, but the remaining patients showed no signs of developing autoimmune hepatitis. We conclude that the DRB1*1301 haplotype is strongly associated with the protracted forms of HAV infection and suggest that the infection allows a sustained release of liver self-antigens. However, other still-unknown susceptibility genes are required for the full development of pediatric AH. (HEPATOLOGY 2001;33:1512-1517

Although molecular diagnosis has been available in our center for the past 10 years, there is no doubt that awareness for early recognition of immunodeficiency should be improved through broader and more comprehensive education programs emphasizing characteristics of patients with immunodeficiencies.

Complete deficiency of complement inhibitor factor I (FI) results in secondary complement deficiency due to uncontrolled spontaneous alternative pathway activation leading to susceptibility to infections. Current genetic examination of two patients with near complete FI deficiency and three patients with no detectable serum FI and also close family members revealed homozygous or compound heterozygous mutations in several domains of FI. These mutations were introduced into recombinant FI and the resulting proteins were purified for functional studies, while transient transfection was used to analyze expression and secretion. The G170V mutation resulted in a protein that was not expressed, whereas the mutations Q232K, C237Y, S250L, I339M and H400L affected secretion. Furthermore, the C237Y and the S250L mutants did not degrade C4b and C3b as efficiently as the WT. The truncated Q336x mutant could be expressed, in vitro, but was not functional because it lacks the serine protease domain. Furthermore, this truncated FI was not detected in serum of the patient. Structural investigations using molecular modeling were performed to predict the potential impact the mutations have on FI structure. This is the first study that investigates, at the functional level, the consequences of molecular defects identified in patients with full FI deficiency.Key words: Complement . Factor I . Human . Immunodeficiency disease IntroductionThe complement system is a very powerful enzymatic cascade, which is beneficial when activated in response to foreign pathogens, but can be destructive when self-tissues give rise to activation. Therefore, the body is equipped with membrane-bound and soluble complement inhibitors, many of which inhibit complement by acting as cofactors for the serine proteinase factor I (FI). In the presence of cofactors, FI inhibits all pathways of complement by degrading the a 0 -chain of the activated complement components C4b and C3b.Several cases of near complete FI deficiencies have been reported and were found to lead to systemic consumption of C3, 310factor H (FH) and factor B (FB) due to uninhibited activation of the alternative pathway. Because of this consumption, opsonization with C3b cannot occur and patients are much more susceptible to recurrent pyogenic infections, such as otitis media, pneumonia and meningitis [1][2][3][4]. There have also been reports of FI-deficient patients who suffer from glomerulonephritis [5] or systemic lupus erythematosus (SLE) [6]. To date, only three studies have identified a molecular defect in FI at the DNA level in patients with a full FI deficiency [7][8][9]. The remainder of the literature comprises reports of clinical presentation [1-6, 10, 11]. The mutant FI proteins in question have not yet been expressed in a recombinant form and therefore there is no information available concerning the effects of these mutations on FI secretion and function. Mutations in FI have also been identified in atypical hemolytic uremic syndrome (aHUS) patients, where they always occur i...

Summary. We investigated the prognostic significance of soluble interleukin 2 receptor (sIL‐2r) levels in the pre‐ and post‐treatment serum of paediatric patients with Langerhans cell histiocytosis (LCH). Serum levels of sIL‐2r from 32 LCH patients and 14 healthy controls were determined using enzyme‐linked immunosorbent assay. The LCH patients were classified, evaluated and treated according to the Histiocyte Society's protocols. The following clinical stages were considered: single‐system disease (A) divided into single‐site (A1; n=4), multiple‐site (A2; n=9), and multisystem disease (B) without organ dysfunction (B1; n=5) and with organ dysfunction (B2; n=14). Pretreatment concentrations of sIL‐2r were markedly increased at diagnosis in LCH patients compared with controls [in pg/ml, median (range) 9200 (1124–40000) versus 610 (343–800)], P < 0·0001. Levels differed significantly between stages A [3250 (1124–11000)] and B [22750 (3400–40000)], P < 0·05, and between substages A2 and B2, P < 0·05. There was a significant correlation between clinical stages and sIL‐2r serum levels, r=0·7996 (P < 0·0001). Patients with ≥ 17500 pg/ml of sIL‐2r had a 30‐month survival of 0·417 (SEM: 0·142) compared with those with levels < 17500 pg/ml, who presented a 30‐month survival of 0·848 (SEM: 0·100) (log‐rank, P < 0·0001). In multivariate analysis, sIL‐2r levels ≥ 17500 pg/ml were found to have greater predictive strength than other well‐known prognostic factors.