In rheumatoid arthritis (RA), locally produced interleukin 15 (IL-15)
can recruit and activate synovial T cells, which then amplify and perp
etuate inflammation through induction of monocyte-derived tumour necro
sis factor alpha (TNF-alpha) via a cell-contact-dependent mechanism. T
hus, IL-15 could play a pivotal role in disease pathogenesis, acting u
pstream of TNF-alpha in orchestrating the induction of a cascade of in
flammatory cytokines.