MyD88 is a key downstream adapter for most Toll-like receptors (TLRs) and interleukin-1 receptors (IL-1Rs). MyD88 deficiency in mice leads to susceptibility to a broad range of pathogens in experimental settings of infection. We describe a distinct situation in a natural setting of human infection. Nine children with autosomal recessive MyD88 deficiency suffered from life-threatening, often recurrent pyogenic bacterial infections, including invasive pneumococcal disease. However, these patients were otherwise healthy, with normal resistance to other microbes. Their clinical status improved with age, but not due to any cellular leakiness in MyD88 deficiency. The MyD88-dependent TLRs and IL-1Rs are therefore essential for protective immunity to a small number of pyogenic bacteria, but redundant for host defense to most natural infections.

Autosomal recessive interleukin-1 receptor-associated kinase (IRAK)-4 and myeloid differentiation factor (MyD)88 deficiencies impair Toll-like receptor (TLR)- and interleukin-1 receptor-mediated immunity. We documented the clinical features and outcome of 48 patients with IRAK-4 deficiency and 12 patients with MyD88 deficiency, from 37 kindreds in 15 countries. The clinical features of IRAK-4 and MyD88 deficiency were indistinguishable. There were no severe viral, parasitic, and fungal diseases, and the range of bacterial infections was narrow. Noninvasive bacterial infections occurred in 52 patients, with a high incidence of infections of the upper respiratory tract and the skin, mostly caused by Pseudomonas aeruginosa and Staphylococcus aureus, respectively. The leading threat was invasive pneumococcal disease, documented in 41 patients (68%) and causing 72 documented invasive infections (52.2%). P. aeruginosa and Staph. aureus documented invasive infections also occurred (16.7% and 16%, respectively, in 25% and 25% of patients). Systemic signs of inflammation were usually weak or delayed. The first invasive infection occurred before the age of 2 years in 53 (88.3%) and in the neonatal period in 19 (32.7%) patients. Multiple or recurrent invasive infections were observed in most survivors (n = 36/50, 72%).

The cytokines controlling the development of human interleukin (IL) 17–producing T helper cells in vitro have been difficult to identify. We addressed the question of the development of human IL-17–producing T helper cells in vivo by quantifying the production and secretion of IL-17 by fresh T cells ex vivo, and by T cell blasts expanded in vitro from patients with particular genetic traits affecting transforming growth factor (TGF) β, IL-1, IL-6, or IL-23 responses. Activating mutations in TGFB1, TGFBR1, and TGFBR2 (Camurati-Engelmann disease and Marfan-like syndromes) and loss-of-function mutations in IRAK4 and MYD88 (Mendelian predisposition to pyogenic bacterial infections) had no detectable impact. In contrast, dominant-negative mutations in STAT3 (autosomal-dominant hyperimmunoglobulin E syndrome) and, to a lesser extent, null mutations in IL12B and IL12RB1 (Mendelian susceptibility to mycobacterial diseases) impaired the development of IL-17–producing T cells. These data suggest that IL-12Rβ1– and STAT-3–dependent signals play a key role in the differentiation and/or expansion of human IL-17–producing T cell populations in vivo.

Loss of function in the kinase IRAK-4 or the adapter MyD88 in humans interrupts a pathway critical for pathogen sensing and ignition of inflammation. Yet patients with loss of function mutations are surprisingly only susceptible to a limited range of pathogens. We employed a systems approach to investigate transcriptome responses following in vitro exposure of patients’ blood to Toll-like receptor and interleukin-1 receptor agonists, and whole pathogens. Responses to purified agonists were globally abolished but variable residual responses were present following exposure to whole pathogens. Further dissection of the latter responses identified a narrow repertoire of immune transcriptional programs affected by loss of MyD88 or IRAK-4 function. This work introduces the use of a systems approach for the global assessment of innate immune responses, and the characterization of human primary immunodeficiencies.

The PTPN22 gene, encoding the lymphoid-specific protein tyrosine phosphatase, a negative regulator in the T-cell activation and development, has been associated with the susceptibility to several autoimmune diseases, including type 1 diabetes. Based on combined case-control and family-based association studies, we replicated the finding of an association of the PTPN22 C1858T (R620W) functional variant with type 1 diabetes, which was independent from the susceptibility status at the insulin gene and at HLA-DR (DR3/4 compared with others). The risk contributed by the 1858T allele was increased in patients with a family history of other autoimmune diseases, further supporting a general role for this variant on autoimmunity. In addition, we found evidence for an association of 1858T allele with the presence of GAD autoantibodies (GADA), which was restricted to patients with long disease duration (>10 years, P < 0.001). This may help define a subgroup of patients with long-term persistence of GADA. The risk conferred by 1858T allele on GAD positivity was additive, and our meta-analysis also supported an additive rather than dominant effect of this variant on type 1 diabetes, similar to previous reports on rheumatoid arthritis and systemic lupus erythematosus. Diabetes 56:522-526, 2007

Interleukin-1 receptor (IL1R)-associated kinase 4 (IRAK4) is a central regulator of innate immune signaling, controlling IL1R and Toll-like receptor (TLR)-mediated responses and containing both scaffolding and kinase activities. Humans deficient in IRAK4 activity have autosomal recessive primary immune deficiency (PID). Here, we characterized the molecular mechanism of dysfunction of two IRAK4 PID variants, G298D and the compound variant R12C (R12C/R391H/T458I). Using these variants and the kinase-inactive D329A variant to delineate the contributions of IRAK4's scaffolding and kinase activities to IL1R signaling, we found that the G298D variant is kinase-inactive and expressed at extremely low levels, acting functionally as a null mutation. The R12C compound variant possessed WT kinase activity, but could not interact with myeloid differentiation primary response 88 (MyD88) and IRAK1, causing impairment of IL-1-induced signaling and cytokine production. Quantitation of IL-1 signaling in IRAK4-deficient cells complemented with either WT or the R12C or D329A variant indicated that the loss of MyD88 interaction had a greater impact on IL-1-induced signaling and cytokine expression than the loss of IRAK4 kinase activity. Importantly, kinase-inactive IRAK4 exhibited a greater association with MyD88 and a weaker association with IRAK1 in IRAK4-deficient cells expressing kinase-inactive IRAK4 and in primary cells treated with a selective IRAK4 inhibitor. Loss of IRAK4 kinase activity only partially inhibited IL-1-induced cytokine and NF-κB signaling. Therefore, the IRAK4-MyD88 scaffolding function is essential for IL-1 signaling, but IRAK4 kinase activity can control IL-1 signal strength by modulating the association of IRAK4, MyD88, and IRAK1.

No abstract

Background: The role of metabolic states in cardiovascular risks among individuals with varying degrees of obesity is unknown. The study aimed to compare cardiometabolic index (CMI), atherogenic index of plasma (AIP), lipid accumulation product (LAP) and novel anthropometric indices in metabolic and non-metabolically obese individual with regard to the role of FTO gene in Iranian adults. Methods: In total, 165 individuals were recruited into this cross-sectional study. Individuals grouped into four groups: metabolic healthy normal-weight (MHNW) individuals, metabolically unhealthy normal-weight (MUNW) individuals, metabolically healthy obese (MHO) individuals and metabolic unhealthy obese (MUO) individuals. The dietary intake was evaluated by food frequency questionnaire (FFQ). The cardiovascular indices (CMI, AIP and LAP) were calculated. A variety of anthropometric indices were calculated, including body adiposity Index (BAI), weight-adjusted-waist index (WWI), A body shape index (ABSI) and waist-height ratio (WHR). The genotypes of FTO-rs9939609 subjects were detected by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Results: The individuals with metabolically unhealthy phenotypes (MUO, MUNW) have higher levels of triglyceride and cardiovascular indices (AIP, LAP and CMI) than the individuals with metabolic healthy phenotypes (MHO, MHNW). With a similar degree of obesity, the anthropometric indices (BAI, WWI and WHR) levels were higher in metabolic unhealthy groups than metabolically healthy groups. The highest frequency of obesity-risk allele AA of FTO gene was observed in MUO, MHO, MUNW and MHNW, respectively. Conclusion: Normal-weight individuals with metabolic unhealthy status are at higher risk for cardiovascular diseases than obese individuals with metabolically healthy status. The genotype frequencies of obesity-risk allele AA of FTO gene were higher in obesity phenotypes than metabolic phenotypes.