Familial Mediterranean fever (FMF) is a recessive inherited autoinflammatory 
syndrome. Patients with FMF have symptoms such as recurrent fever and abdominal 
pain, sometimes accompanied by arthralgia. Biopsy specimens have revealed 
substantial neutrophil infiltration into synovia. FMF patients have a mutation 
in the Mediterranean fever gene, encoding pyrin, which is known to regulate the 
inflammasome, a platform for processing interleukin (IL)-1β. FMF patients 
heterozygous for E148Q mutation, heterozygous for M694I mutation, or combined 
heterozygous for E148Q and M694I mutations, which were found to be major 
mutations in an FMF study group in Japan, suffer from arthritis, the severity of 
which is likely to be lower than in FMF patients with M694V mutations. 
Expression plasmids of wild-type (WT) pyrin and mutated pyrin, such as E148Q, 
M694I, M694V, and E148Q+M694I, were constructed, and SW982 synovial sarcoma 
cells were transfected with these expression plasmids. IL-8 and IL-6 were 
spontaneously secreted from the culture supernatant of SW982 cells without any 
stimulation, whereas IL-1β and TNF-α could not be detected even when stimulated 
with lipopolysaccharide. Notably, two inflammasome components, ASC and 
caspase-1, could not be detected in SW982 cells by Western blotting. IL-8 but 
not IL-6 secretion from SW982 cells was largely suppressed by WT pyrin, but less 
suppressed by mutated pyrin, which appeared to become weaker in the order of 
E148Q, M694I, E148Q+M694I, and M694V mutations. As for IL-8 and IL-6, similar 
results were obtained using stable THP-1 cells expressing the WT pyrin or 
mutated pyrins, such as M694V or E148Q, when stimulated by LPS. In addition, 
IL-8 secretion from mononuclear cells of FMF patients was significantly higher 
than that of healthy volunteers when incubated on a culture plate. Thus, our 
results suggest that IL-8 secretion from SW982 synovial sarcoma cells suppressed 
by pyrin independently of inflammasome is affected by pyrin mutations, which may 
reflect the activity in FMF arthritis.