BUILDING UP OF AN ANIMAL MODEL OF CONDITIONED IMMUNOSUPPRESSION AND ANALYSIS OF ITS POSSIBLE MECHANISM

In the present study,camphor edor and intraperitoneal(ip)injection ofcyclophosphamide(CY)were used as conditional and unconditional stimulus,respectively,in mice.Mice were exposed to camphor edor for 1h in their cage in a closed area followed by an ip injection ofCY(75 mg·kg^-1)This association trial session was repeated once on the next day.Delayed type hypersensitivityresponse(DTH)was induced as follows:six days after the second association trial session the micewere sensitized by smearing dinitrochlorobenezene(DNCB)on their aMominal skin,The mice werechallenged by smearing DNCB on the left ear 5 days after the antigen sensitization,The left and rightears were removed 24 h after the challenge and weighed,the weight ratio of left/ right ears wascalculated for identification of the response,The ratio was 1.30±0.113(±s,P<0.001),indicating that the challenged ear was heavier than the other and DTH was induced.In theunconditioned response(UCR)group, CY(75 mg·kg^-1)was given 24 h prior to the challenge andthe ratio was 1.09±0.024(P<0.001)indicating that DTH was uppressed by unconditional stimulus(CY).In the conditioned response(CR) group mice were reexposed to camphor edor 24 h prior to thechallenge and normal saline was injected instead of CY,The ratio was 1.13±0.074(P<0.001),indicating that DTH was also suppressed by conditional stimulus(camphor odor).These results showthat a conditioned immunosuppressive response was induced,In the experiment, many other groups,including unconditioned response group, CYE group and camphor control group,were described inmore details in the text.In order to further analyse the mechanisms of the conditioned response,theblood from the mice in CR group was obtained 6 h after reexposure to camphor odor and the serum wasinjected to normal mice 6h prior to the challenge,DTH was found to be suppressed significantly whencompared with the mice injected with normal serum,The conditioned serum was dialyzed against amembrane with a 10 000 molecular weight cut off.The suppressive activity of the conditioned serumdisapf1eared, suggesting that the molecular weight of the suppressive element in the serum was probablyless than 10000kDa.