Absence of interleukin-17 receptor a signaling prevents autoimmune inflammation of the joint and leads to a Th2-like phenotype in collagen-induced arthritis

OBJECTIVE

Interleukin-17A (IL-17A) signals through the IL-17 receptor (IL-17R) A/C heterodimer. IL-17RA serves as a common receptor subunit for several IL-17 cytokine family members. Lack of IL-17RA signaling may therefore have additional effects beyond those of lack of IL-17A alone. The present study was undertaken to determine the role of IL-17RA signaling in autoimmune arthritis.

METHODS

Disease incidence and severity were scored in type II collagen-treated wild-type, IL-17RA-deficient, and IL-23p19-deficient mice. T helper cell profiles and humoral immune responses were analyzed at several time points. Pathogenicity of T cells and total splenocytes was determined by in vitro functional assay. IL-17RA signaling was blocked in vivo in mice with antigen-induced arthritis (AIA).

RESULTS

Comparable to the findings in IL-23p19-deficient mice, IL-17RA-deficient mice were completely protected against the development of collagen-induced arthritis (CIA). However, IL-17RA-deficient mice exhibited an increased number of IL-4-producing CD4+ T cells, distinct from IL-17A+CD4+ T cells. This was associated with fewer plasma cells, lower production of pathogenic IgG2c antibody, and increased production of IgG1 antibody. Both isolated CD4+ T cells and total splenocytes from IL-17RA-deficient mice had a reduced ability to induce IL-6 production by synovial fibroblasts in the setting of CIA, in a functional in vitro assay. Furthermore, blocking of IL-17RA signaling in AIA reduced synovial inflammation.

CONCLUSION

These results demonstrate that absence of IL-17RA leads to a Th2-like phenotype characterized by IL-4 production and suggest that IL-17RA signaling plays a critical role in the regulation of IL-4 in CIA and the development of autoimmune inflammation of the joint.

Microbiological spectrum and susceptibility patterns of pathogens causing bacteraemia in paediatric febrile neutropenic oncology patients: comparison between two consecutive time periods with use of different antibiotic treatment protocols

This study was devised to look at trends in the microbiological spectrum and susceptibility patterns of pathogens causing bacteraemia in paediatric febrile oncology patients. The retrospective study compared various microbiological aspects recorded for febrile oncology neutropenic patients treated with two different empirical antibiotic regimens (ceftazidime plus gentamicin during 1998-1999 and piperacillin/tazobactam plus amikacin during 2000-2002). Eighty-one bacteraemic episodes occurred in 41 patients. Overall, 132 (34 during 1998-1999 and 98 during 2000-2002) organisms were isolated: 84 (65%) Gram-negative bacteria, 39 (30%) Gram-positive bacteria and 7 (5%) fungi. Enterobacter spp. incidence decreased from 18 to 6% (P=0.07) while the recovery rates of Gram-positive organisms increased from 24 to 32% (P=0.4) during 2000-2002 compared with 1998-1999. MRSA were not isolated from any episode of bacteraemia. Five (18%) of the 28 Escherichia coli and Klebsiella spp. isolates were beta-lactamase producers (80% [4/5] isolated during 2000-2002). Twenty-seven of 28, 27/27, 23/28, 20/25 and 27/28 of these isolates were susceptible to imipenem, piperacillin/tazobactam, gentamicin, ceftazidime and ciprofloxacin, respectively. Thirty-two of 34 (94%) and 60/74 (81%) of the Gram-negative organisms isolated during 2000-2002 were susceptible to piperacillin/tazobactam and ceftazidime, respectively (P=0.076). No major differences in the microbial spectrum and antibiotic susceptibilities were recorded between the two consecutive study periods. An increase in the number of extended beta-lactamase producing E. coli and Klebsiella spp. occurred during 2000-2002. All beta-lactamase producing organisms were susceptible to piperacillin/tazobactam and initial empirical therapy with piperacillin/tazobactam was more appropriate than ceftazidime to cover most of the pathogens causing bacteraemia.