Objective To observe the influence of moxibustion of "Shenshu"(BL 23) and "Zusanli"(ST 36) on the microstructure of synovial cells in the knee-joint in rheumatoid arthritis(RA) rats so as to study its underlying mechanism in anti-inflammatory immune effect.Methods A total of 120 Wistar rats were randomized into normal control

model

acupuncture

moxi-bustion

CO2-laser and medication groups(n=20/group).RA model was duplicated by raising the rats in a windy(electro-fan blowing)

cold [(6±2)℃]and wet(80%-90%)environment for 12h/d and 20 days

followed by injecting Freund's complete adjuvant(0.15mL) into the rat's ankle.Moxibustion or acupuncture or CO2 laser(10.6μm) irradiation was applied to "Shenshu"(BL 23) and "Zusanli"(ST 36) for 20min

once daily for 15 days.Intragastric perfusion of Leigongteng(Tripterygium Wilfordii Hook.f.) was given to medication group

8 mg/kg

once daily for 15 days.The thoracic gland index [weight of the thoracic gland(mg)/ body weight(g)×100%] and spleen index [weight of the spleen(mg)/body weight(g)×100%] were calculated after killing the rats under anesthesia.The ultrastructure of synovial cells of the knee-joint was observed by using transmission electron microscopy.Results In comparison with the normal control group

the thoracic gland index in the model group was decreased significantly(P<0.01)

while the spleen index of the model group increased considerably(P<0.05).In comparison with the model group

the thoracic gland indexes in the acupuncture

moxibustion

CO2-laser and medication groups were increased significantly(P<0.05

P<0.01)

whereas the spleen indexes in the four groups decreased evidently(P<0.05).No significant diffe-rences were found among the acupuncture

moxibustion

CO2-laser and medication groups in up-regulating the thoracic gland index and down-regulating the spleen index(P>0.05).After modeling

the synoviocytes of the knee-joint were impaired remarkably

exhibiting incomplete cellular membrane

some prolapsed organelles

marginalized stained granules in the cellular nucleus

vague nuclear membrane

enlarged rough endoplasmic reticulum

reduction in the number of mitochondria with vacuolization degeneration and multiple lysosomes.But

the pathological changes of the ultrastructure of most synoviocytes in the acupuncture

moxibustion

CO2-laser and medication groups were relatively milder.Conclusion Moxibustion can protect the immune organs(thoracic gland and spleen) from injury and improve pathological changes of the ultrastructure of local synoviocytes in RA rats.