Inflammasome-mediated disease animal models reveal roles for innate but not adaptive immunity.

NLRP3 nucleates the inflammasome, a protein complex responsible for cleavage of prointerleukin-1beta (IL-1beta) to its active form. Mutations in the NLRP3 gene cause the autoinflammatory disease spectrum cryopyrin-associated periodic syndromes (CAPS). The central role of IL-1beta in CAPS is supported by the response to IL-1-targeted therapy. We developed two Nlrp3 mutant knockin mouse strains to model CAPS to examine the role of other inflammatory mediators and adaptive immune responses in an innate immune-driven disease. These mice had systemic inflammation and poor growth, similar to some human CAPS patients, and demonstrated early mortality, primarily mediated by myeloid cells. Mating these mutant mice to various gene mutant backgrounds showed that the mouse disease phenotype required an intact inflammasome, was only partially dependent on IL-1beta, and was independent of T cells. These data suggest that CAPS are true inflammasome-mediated diseases and provide insight for more common inflammatory disorders.

Cold urticaria, immunodeficiency, and autoimmunity related to PLCG2 deletions.

BACKGROUND: Mendelian analysis of disorders of immune regulation can provide insight into molecular pathways associated with host defense and immune tolerance. METHODS: We identified three families with a dominantly inherited complex of cold-induced urticaria, antibody deficiency, and susceptibility to infection and autoimmunity. Immunophenotyping methods included flow cytometry, analysis of serum immunoglobulins and autoantibodies, lymphocyte stimulation, and enzymatic assays. Genetic studies included linkage analysis, targeted Sanger sequencing, and next-generation whole-genome sequencing. RESULTS: Cold urticaria occurred in all affected subjects. Other, variable manifestations included atopy, granulomatous rash, autoimmune thyroiditis, the presence of antinuclear antibodies, sinopulmonary infections, and common variable immunodeficiency. Levels of serum IgM and IgA and circulating natural killer cells and class-switched memory B cells were reduced. Linkage analysis showed a 7-Mb candidate interval on chromosome 16q in one family, overlapping by 3.5 Mb a disease-associated haplotype in a smaller family. This interval includes PLCG2, encoding phospholipase Cγ(2) (PLCγ(2)), a signaling molecule expressed in B cells, natural killer cells, and mast cells. Sequencing of complementary DNA revealed heterozygous transcripts lacking exon 19 in two families and lacking exons 20 through 22 in a third family. Genomic sequencing identified three distinct in-frame deletions that cosegregated with disease. These deletions, located within a region encoding an autoinhibitory domain, result in protein products with constitutive phospholipase activity. PLCG2-expressing cells had diminished cellular signaling at 37°C but enhanced signaling at subphysiologic temperatures. CONCLUSIONS: Genomic deletions in PLCG2 cause gain of PLCγ(2) function, leading to signaling abnormalities in multiple leukocyte subsets and a phenotype encompassing both excessive and deficient immune function. (Funded by the National Institutes of Health Intramural Research Programs and others.).

Mutations of complement factor I and potential mechanisms of neuroinflammation in acute hemorrhagic leukoencephalitis.

PURPOSE: Acute Hemorrhagic Leukoencephalitis (AHLE) is a rare demyelinating disorder of acute onset, rapid deterioration and significant morbidity and mortality. Most often described as a post-infectious complication of an upper respiratory illness, its precise pathophysiology remains unclear. We describe two pediatric patients with AHLE with partial complement factor I (FI) deficiency whose successful treatment included the interleukin-1 (IL-1) receptor antagonist, anakinra, implicating a role for FI and IL-1 in this disorder. METHODS: Extensive clinical workup of two patients presenting with AHLE revealed complement abnormalities, specifically related to the alternative pathway and its regulator, FI. Aggressive management with steroids, immunoglobulin, and anakinra ultimately led to improvement of clinical status and near return to neurologic baseline in both patients. Genetic sequencing of the FI coding regions of the patients and their families was performed. In vitro protein expression studies and immunohistochemistry of fixed brain tissue was used to investigate pathogenic mechanisms. RESULTS: Two novel mutations in FI were identified in our patients, which result in failure to secrete FI. Immunohistochemical evaluation of brain tissue demonstrated positive staining for C3, membrane attack complex (MAC) and IL-1. CONCLUSIONS: We propose AHLE is an unreported, rare phenotype for partial FI deficiency. The upregulation of C3, MAC and IL-1 with subsequent demyelination support a pathologic role for complement activation in AHLE, and suggest anakinra as an important adjunctive therapy in this disease.

Familial atypical cold urticaria: description of a new hereditary disease.

BACKGROUND: Acquired cold urticaria (ACU) is usually a self-limited, sporadic, cutaneous disease diagnosed based on history and a positive cold stimulation time test (CSTT) result. We describe 3 unrelated families (A, B, and C) with lifelong atypical cold urticaria distinguished from ACU and familial cold autoinflammatory syndrome. OBJECTIVE: We sought to describe a new hereditary disease of cold urticaria and study its pathogenesis. METHODS: Questionnaires, interviews, physical examinations, skin testing, and biopsies were performed. Absolute values, means, and prevalence percentages of data are reported. RESULTS: Thirty-five subjects are described with familial atypical cold urticaria (FACU; family A, 17; family B, 8; and family C, 10) displaying an autosomal dominant pattern of inheritance. All tested subjects had negative CSTT results. Completed questionnaires from affected and unaffected members of families A and B (n = 35) revealed that all affected subjects had lifelong symptoms that began in early childhood with pruritus, erythema, and urticaria after cold exposure. Angioedema (family A, 23%; family B, 42%) and syncope, near syncope, or both (family A, 46%; family B, 86%) were also present. Triggers included cold atmosphere (100%), aquatic activities (family A, 92%; family B, 100%), handling cold objects (family A, 54%; family B, 71%), and ingestion of cold foods or beverages (family A, 69%; family B, 100%). Skin biopsy specimens demonstrated a mast cell infiltrate with the appearance of degranulation after cold challenge. CONCLUSIONS: FACU is a new cold-induced inherited disease that is different than ACU in its natural history, atmospheric cold elicitation, severity of systemic reactions, and CSTT results. FACU differs from familial cold autoinflammatory syndrome in symptom timing and the absence of fever, chills, and joint pain. The cause is suspected to be mast cell related. Treatment of reactions is similar to that for ACU. Further evaluation of pathogenesis and genetics is warranted.