Finding 1: Because of our interest in patients with symptoms of atopy in the context of unidentified syndromes, we have been studying a series of families with cold urticaria, antibody deficiency, autoimmunity and granulomatous disease segregating in an autosomal dominant pattern. We have named this syndrome PLAID, as described in our report in the New England Journal of Medicine. Patients have low IgM and IgA, low NK cells, normal T cells and low to absent class-switched B cells. In collaboration with Dr. Daniel Kastner's lab, we found that the disease is caused by genomic deletions in PLCG2. The deletions are in an autoregulatory domain, leading to gain of PLCG2 enzymatic function but loss of distal signaling function, resulting in defective calcium flux and ERK phosphorylation in response to surface receptor cross-linking in B and NK cells, poor in vitro expansion and switched immunoglobulin secretion in response to SAC and CpG, and abnormal B-cell receptor editing in B-cells. We have found that the cold spontaneously activates certain cells in these patients, such as B cells and mast cells. Neutrophils from these patients appear to be constitutively active, perhaps explaining the granulomatous disease seen in some of the patients. In addition, again in collaboration with the Kastner lab, we have participated in the identification and cellular study of another family with an autoinflammatory disorder affecting lungs, skin and eyes, as well as loss of class switched B cells. This family has heterozygous point mutations in the same SH2 domain of PLCg2, which is deleted in PLAID. We have termed this disease APLAID, to reflect the autoinflammatory component. We have characterized major differences between PLAID and APLAID patients, including the increased cellular responses to ligand and lack of cold response in APLAID patients. These results were published in the American Journal of Human Genetics. Finding 2: In our study of patients with immune deficiencies and atopic phenotypes, we have developed a flow-based assay for assessing multiple STAT responses to individual cytokines. Using this tool, in collaboration with Dr. Steve Holland's lab, we have found a family with invasive cryptosporidial infections, bronchiectasis and antibody deficiency with marked elevations in serum IgE. We found absent IL-21 signaling in these patients. In collaboration with Christoph Klein in Munich, we found a 6 bp in-frame deletion in the IL-21 receptor in these patients. Dr. Klein had followed two patients with similar phenotypes and found an independent mutation in the IL-21 receptor. The report of ours and Dr. Klein's patients was published in the Journal of Experimental Medicine. In addition, we have used this tool to identify patients with gain of function mutations in STAT1 from the Holland lab and in collaboration with Neil Romberg at Yale, which lead to a variety of clinical phenotypes, and we have made inroads into the pathogenesis of these mutations leading to the discrete phenotypes. Three different manuscripts describing these findings were published in the Journal of Allergy and Clinical Immunology. The clinical and laboratory overlap between STAT3 loss-of-function patients, STAT1 gain-of-function patients, and IL-21r loss of function patients can be gleaned from these various reports, and provides the basis for ongoing investigation into these common pathways. Finding 3: Using whole exome sequencing, we found recessive mutations in phosphoglucomutase 3 (PGM3) which lead to a syndrome of severe allergy, immune deficiency and neurocognitive abnormalities. The patients have severe atopic dermatitis and high IgE, as well as high IgA and IgG, low CD8 and memory B-cell numbers, dysmyelination, and abnormally increased Th2 and Th17 cytokine production. The mutations in PGM3 lead to a reduction in normal protein glycosylation and segregate perfectly with disease in two different multiplex families affected. The results are under review at a major Allergy and Clinical Immunology journal. Finding 4: In our efforts to describe familial inheritance of allergic disease, we have identified 9 families with an autosomal dominant inheritance of elevated basal tryptase levels in the absence of any signs of mastocytosis. Affected family members have cutaneous flushing, episodic gastrointestinal pain, food allergy and anaphylaxis, and, in a subset of patients, connective tissue abnormalties reminiscent of Ehlers-Danlos syndrome, hypermobility type. Patient basophils have a degranulation defect, perhaps due to anergy ex-vivo, and in the 5 families in whom bone marrow biopsies were done, there was a significant elevation in mast cell number, despite the lack of morphologic evidence or scale of mastocytosis.
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