The sustained inflammatory disease observed in HLH caused by lesions affecting the exocytic machinery is presumed to result from failure to eradicate the causal microbe, which accumulatesin vivoand stimulates expansion of antigen-specific lymphoid clones. TLR signaling pathways to elicit IL-1 production. IL-1 signaling via MyD88 elicits inflammatory disease. Keywords:Ptpn6, Toll-like receptors A large body of evidence points to participation of the innate immune response in the pathogenesis of autoimmune disease (1,2). The Toll-like receptors, Nod-like receptors, and RIG-I-like helicases sense microbial signature and endogenous molecules and initiate signaling leading to the production of proinflammatory cytokines. These cytokines, including types I and II IFN, TNF, IL-1, IL-6, and IL-12, mediate inflammatory responses to contamination and enhance responses of the adaptive immune system. Moreover, their overproduction is often associated with autoimmune or autoinflammatory diseases. For example, type I IFN has been implicated in the development of systemic lupus erythematosus (SLE) (1), TNF contributes to the pathology of rheumatoid arthritis (3), and IL-1 contributes to neonatal onset multisystem inflammatory disease (NOMID) (4). Themotheatenmutants (meandviable motheaten,me-v) develop autoimmune disease and inflammation with features similar to SLE.Motheatenmice carry null or hypomorphic alleles ofPtpn6, encoding the hematopoietic protein tyrosine phosphatase SHP1 (57), which is thought to down-regulate signaling from cytokine receptors, B and T cell receptors, chemokine receptors, receptor tyrosine kinases, and integrins (8).Ptpn6meandPtpn6me-vhomozygotes or compound heterozygotes are immunodeficient and develop systemic inflammation and autoimmunity, marked by alopecia, glomerulonephritis, dermatitis, inflammation of the paws, and interstitial pneumonitis, which ultimately causes death (9,10). In both strains, there is overproduction and accumulation of macrophages and neutrophils in the lungs, skin, and extremities, and elevated concentrations of serum immunoglobulins and autoantibodies (1012). In double mutantPtpn6me-v/me-vRag1/mice, which lack B and T cells and cannot generate autoantibodies, severe inflammatory lesions still develop, in which macrophages and granulocytes infiltrate healthy tissues. This indicates that chronic inflammatory disease progression inPtpn6me-vmutants does not require the adaptive immune response (13). However, mice lackingPtpn6expression only in B lymphocytes develop both autoimmunity and chronic inflammatory disease, as evidenced by increased levels of serum immunoglobulins reactive to single- and double-stranded DNA, lymphocytic infiltrates of the lung and liver, and glomerulonephritis (14). These data show that SHP1 deficiency need affect only B cells to cause autoimmunity featuring autoantibody production. Augmented cytokine production or signaling has been proposed to contribute to the development of disease inmotheatenmutants (15,16). Here, we describe a hypomorphic allele ofPtpn6(m1Btlr, designatedspin) detected because it elicits chronic inflammatory and autoimmune disease. By screening the suppressive effects of mutations at other loci and deriving the mice into a germ-free (GF) environment, we have concluded that the inflammatory phenotype requires MyD88, IRAK4, and the IL-1 receptor, but not type I or type II IFNs, or TNF. Inflammation cannot be expressed in the absence of commensal microbes. == Results == == spinPhenotype. == A recessive inflammatory Bleomycin hydrochloride phenotype (calledspinto denote spontaneous inflammation) was observed in a G3 mouse homozygous for mutations induced byN-ethyl-N-nitrosourea (ENU) on Bleomycin hydrochloride a pure C57BL/6J background. The plantar surfaces of the feet develop inflamed, natural, weeping lesions (Fig. 1). By following this visible phenotype, a homozygous stock ofspinmutants was established. Around the C57BL/6 background, inflammation is usually 90% penetrant in both males and females scored between 10 and 25 Bleomycin hydrochloride weeks of age. Histological examination of the feet revealed thickening of the epidermis, microabscesses in the epidermal and dermal layers, bone marrow hyperplasia, and a neutrophilic infiltrate in the dermal layer [supporting information (SI) Fig. S1AD]. Mixed inflammatory infiltrates were also noted in the salivary glands (Fig. S1EandF) and lungs (Fig. S1GandH) ofspinmice. == Fig. 1. == Chronic inflammation in homozygousspinmutants. Foot lesions develop inspinhomozygotes from 6 weeks of age. Two representative foot lesions fromspinhomozygotes are shown. Before 5 weeks of age,spinmice show no indicators of foot Rabbit polyclonal to IQCE inflammation and have normal frequencies and total numbers of myeloid and erythroid cells in the bone marrow, Bleomycin hydrochloride spleen, and peripheral blood (Table.