Rushani Saltzman

IL-2 induces a WAVE2-dependent pathway for actin reorganization that enables WASp-independent human NK cell function

Wiskott-Aldrich syndrome (WAS) is a primary immunodeficiency associated with an increased susceptibility to herpesvirus infection and hematologic malignancy as well as a deficiency of NK cell function. It is caused by defective WAS protein (WASp). WASp facilitates filamentous actin (F-actin) branching and is required for F-actin accumulation at the NK cell immunological synapse and NK cell cytotoxicity ex vivo. Importantly, the function of WASp-deficient NK cells can be restored in vitro after exposure to IL-2, but the mechanisms underlying this remain unknown. Using a WASp inhibitor as well as cells from patients with WAS, we have defined a direct effect of IL-2 signaling upon F-actin that is independent of WASp function. We found that IL-2 treatment of a patient with WAS enhanced the cytotoxicity of their NK cells and the F-actin content at the immunological synapses formed by their NK cells. IL-2 stimulation of NK cells in vitro activated the WASp homolog WAVE2, which was required for inducing WASp-independent NK cell function, but not for baseline activity. Thus, WAVE2 and WASp define parallel pathways to F-actin reorganization and function in human NK cells; although WAVE2 was not required for NK cell innate function, it was accessible through adaptive immunity via IL-2. These results demonstrate how overlapping cytoskeletal activities can utilize immunologically distinct pathways to achieve synonymous immune function.

Invariant natural killer T cells from children with versus without food allergy exhibit differential responsiveness to milk-derived sphingomyelin.

BACKGROUND A key immunologic feature of food allergy (FA) is the presence of a T(h)2-type cytokine bias. Ligation of the invariant natural killer T cell (iNKT) T-cell receptor (TCR) by sphingolipids presented via the CD1d molecule leads to copious secretion of T(h)2-type cytokines. Major food allergens (eg, milk, egg) are the richest dietary source of sphingolipids (food-derived sphingolipids [food-SLs]). Nonetheless, the role of iNKTs in FA is unknown. OBJECTIVE To investigate the role of iNKTs in FA and to assess whether food-SL-CD1d complexes can engage the iNKT-TCR and induce iNKT functions. METHODS PBMCs from 15 children with cows milk allergy (MA), 12 children tolerant to cows milk but with allergy to egg, and 13 healthy controls were incubated with α-galactosylceramide (αGal), cows milk-sphingomyelin, or hens egg-ceramide. iNKTs were quantified, and their cytokine production and proliferation were assessed. Human CD1d tetramers loaded with milk-sphingomyelin or egg-ceramide were used to determine food-SL binding to the iNKT-TCR. RESULTS Milk-sphingomyelin, but not egg-ceramide, can engage the iNKT-TCR and induce iNKT proliferation and T(h)2-type cytokine secretion. Children with FA, especially those with MA, had significantly fewer peripheral blood iNKTs and their iNKTs exhibited a greater T(h)2 response to αGal and milk-sphingomyelin than iNKTs of healthy controls. CONCLUSION iNKTs from children with FA, especially those with MA, are reduced in number and exhibit a T(h)2 bias in response to αGal and milk-sphingomyelin. These data suggest a potential role for iNKTs in FA.

Food allergies and atopic dermatitis: differentiating myth from reality.

PEDIATRIC ANNALS 38:2 | FEBRUARY 2009 Food Allergies and Atopic Dermatitis: Differentiating Myth from Reality Adverse food reactions or food allergy can be the source of stress for many families. Some studies have assessed the quality of life for children with food allergy. One study showed that parents of children with food allergy report that family activities and general health perception are negatively affected.1 Cohen et al, using principles established in measuring disease-specifi c, health-related quality of life instruments, found that multiple domains are affected in families with food allergy including school, camp, social activities involving food, vacations, children in the care of others, restaurant meals, and being near other children who are eating. Parents also reported anxiety and frustration over nutritional issues, worry over not being able to help their child with a reaction, and whether their child eventually will overcome the allergy.2 Managing food allergy is an ongoing process involving cooperation between the parent and physician. Determining the etiology of food reactions can better guide therapies.3 Food allergies or adverse reactions to food can be defi ned in many different ways. A standard classifi cation is used to split the reactions into non-immunogenic or immunogenic causes. Non-immunogenic reactions can be physical, toxic reactions

Clinical conditions associated with PCP in children

Pneumocystis jirovecii is a leading cause of opportunistic infections among the immune compromised. During the 1980s, attention focused on patients with HIV, however, with the advent of anti‐retroviral therapy, we wished to revisit the question of underlying diseases associated with Pneumocystis pneumonia in children. We identified 80 cases from 1986 to 2006 and performed a retrospective chart review to identify clinical characteristics for each of the cases. HIV was the single most common associated underlying condition seen in this cohort, accounting for 39% of the cases overall, however, it was seen in just 15% of the cases since 1998. Transplant recipients and oncology patients together comprised another 39% of the cases, with 9% of cases attributed to primary immune deficiency and another 9% of cases associated with less well‐recognized causes of susceptibility. This study documents the ongoing need for vigilance to diagnose Pneumocystis pneumonia in less well‐recognized clinical scenarios. Pediatr Pulmonol. 2012; 47:510–516.

Congenital alterations of NEMO glutamic acid 223 result in hypohidrotic ectodermal dysplasia and immunodeficiency with normal serum IgG levels

BACKGROUND Hypomorphic mutations in the nuclear factor-κB (NF-κB) essential modulator (NEMO) gene result in a variable syndrome of somatic and immunologic abnormalities. Clinically relevant genotype-phenotype associations are essential to understanding this complex disease. OBJECTIVE To study 2 unrelated boys with novel NEMO mutations altering codon 223 for similarity in phenotype in consideration of potential genotype-phenotype associations. METHODS Clinical and laboratory features, including cell counts, immunoglobulin quantity and quality, natural killer cell cytotoxicity, and Toll-like and tumor necrosis factor receptor signaling, were evaluated. Because both mutations affected NEMO codon 223 and were novel, consideration was given to new potential genotype-phenotype associations. RESULTS Both patients were diagnosed as having hypohidrotic ectodermal dysplasia and had severe or recurrent infections. One had recurrent sinopulmonary infections and the other necrotizing soft tissue methicillin-resistant Staphylococcus aureus infection and Streptococcus anginosus subdural empyema with bacteremia. NEMO gene sequence demonstrated a 3-nucleotide deletion (c.667_669delGAG) in one patient and a substitution (667G>A) in the other. These findings predict either the deletion of NEMO glutamic acid 223 or it being replaced with lysine, respectively. Both patients had normal serum IgG levels but poor specific antibodies. Natural killer cell cytotoxicity and Toll-like and tumor necrosis factor receptor signaling were also impaired. Serious bacterial infection did not occur in both patients after immunoglobulin replacement therapy. CONCLUSIONS Two different novel mutations affecting NEMO glutamic acid 223 resulted in clinically relevant similar phenotypes, providing further evidence to support genotype-phenotype correlations in this disease. They suggest NEMO residue 223 is required for ectodermal development and immunity and is apparently dispensable for quantitative IgG production but may be required for specific antibody production.

Novel mutation in STXBP2 prevents IL-2–induced natural killer cell cytotoxicity

We have identified dizygotic twins with a novel syntaxin-binding protein 2 (STXBP2) mutation, where cytotoxicity cannot be restored with IL-2. This defines STXBP2 as an absolute requirement for NK cell cytotoxic function.

Invariant natural killer cells change after an oral allergy desensitization protocol for cow's milk

Cow milk (CM) allergy (CMA) affects up to 3% of the paediatric population and recent data suggest that only about 50% will outgrow by age 8. Oral immunotherapy (OIT) is a type of immune‐modulating treatment that is able to induce desensitization to food allergens, to increase tolerance threshold, to reduce the risk of anaphylaxis, and to improve the patients quality of life. The examination of the immunological changes observed during the establishment of food allergy (FA) desensitization in FA patients is a window into the pathogenesis of food allergy and food tolerance development. In this pathway, we have previously found that invariant natural killer T cells (iNKTs) are involved in CM allergy sensitization and now examine their role in OIT.

Food Protein-Induced Enterocolitis Syndrome Food Challenges: Experience from a Large Referral Center

BACKGROUND Food protein-induced enterocolitis syndrome (FPIES) is a non-IgE-mediated food allergy that is diagnosed based on clinical findings, but can be confirmed with oral food challenge (OFC). OFC is more often performed to assess the development of tolerance. Most studies describing OFCs in FPIES are limited in size. OBJECTIVE We sought to describe our experience with OFCs using our FPIES protocol. Patients were given one-third of serving size with a 4-hour observation period, followed by home titration to full dose. METHODS We conducted a retrospective chart review of patients who underwent OFC via the FPIES protocol from 2014 to 2017. Data regarding the history of reaction, age at the time of challenge, and reactions during challenge or with home introduction were collected. RESULTS A total of 169 OFCs were completed under the FPIES protocol, in 119 patients to 19 different foods. Thirty challenges (18%) were positive, with 17 challenges (10%) during initial challenge and 13 (7.7%) during home dosing. Most reactions during initial challenge required intravenous fluids (IVF), but hypotension was uncommon. One hundred thirty-nine (82%) OFCs were negative with home introduction, indicating tolerance to the challenged foods. The mean age of passing a challenge to milk, soy, and grain was earlier than that of other solid foods. CONCLUSIONS Our data suggest that our FPIES OFC protocol is safe. Early administration of IVF may prevent the development of hypotension. It is difficult to stratify the risk of severe or delayed reaction based on patient characteristics, and more data are needed to identify those appropriate for home introduction.

Differences in egg and milk food challenge outcomes based on tolerance to the baked form

BACKGROUND Previous studies suggest inclusion of baked egg and milk in the diet of children with egg or cows milk (CM) allergy might positively affect native tolerance. However, differences in native food reactivity based on historical baked tolerance are not fully understood. OBJECTIVE To assess differences in native egg and CM oral food challenge (OFC) outcomes based on presenting history of tolerance and exposure to these foods in the baked form. METHODS This study is a retrospective review of all egg and CM OFCs at the Childrens Hospital of Philadelphia (Philadelphia, Pennsylvania) over 4 years (N = 580). History of baked ingestion was compared with OFC pass rate, eliciting dose, epinephrine use, reaction classification, and recent skin test reaction or specific immunoglobulin E level. RESULTS There were 115 egg- and 70 CM-positive challenge reactions, with most eliciting anaphylaxis. Children tolerating baked egg passed OFC more frequently (75%) compared with children who avoided baked egg (58%; P = .01) or never ingested egg (45%; P < .0001). For positive reactions, children tolerant of baked egg reacted at higher eliciting doses of native egg (median 3.0 g, range 0.125-15.75 g) compared with those avoiding baked egg (median 0.69 g, range 0.13-10.0 g; P = .03) and those with no egg exposure (median 0.88 g, range 0.13-13.88 g; P = .01). Further, epinephrine use was lower in children tolerating baked egg (10%) compared with children avoiding baked egg (22%; P = .02) and compared with children who never ingested egg (32%; P = .0001). These differences were not observed for CM challenges. CONCLUSION Children who historically tolerated baked egg were less sensitive to native egg during OFC compared with children whose baked reactivity was largely unknown.

Gastrointestinal Syndromes Associated with Food Allergies

The relationship between food and gastrointestinal (GI) symptoms is not new. From diarrhea due to food contamination to hives and vomiting from egg—a link has been made.