OBJECTIVETo investigate the influence of escharectomy at different time-points after burn injury on the lymphocyte apoptosis and the antigen presentation function of monocytes in peripheral blood of scalded rats.

METHODSOne hundred and thirty-six Wistar rats were randomly divided into normal control ( C,n = 8 ), scald ( S, n = 64,without treatment after scald) , A ( n = 40, with escharectomy at 36 post-burn hour( PSH) ) , B ( n = 24, with escharectomy at 72 PSH ) groups. The rats in A , B, S groups were inflicted with 30% TBSA full-thickness scald. The rats in S group were sacrificed on 6,12,24,72,120,168,216, 288 PSH, while those in A and B groups were sacrificed at 72 -288 PSH, 168 -288PSH, respectively. The rats in C group were also sacrificed as control. The apoptotic rate of peripheral lymphocytes, the positive expression rate of MHC- II in mononuclear cells, the changes in concentration of IL-4 and gamma-IFN were determined in each group. The correlation of above indices were also analyzed.

RESULTS(1) The apoptotic rate of peripheral lymphocyte in S group were increased dramatically at 6PSH, peaking at 24 PSH( 18. 19+/-1.42% ) , then decreasing gradually, reaching the lowest level at 72 PSH(8. 25+/-0.56% ) , then it increased gradually again, approaching almost the peak value at 288 PSH( 17.81 +/- 1.99% ). The values were all obviously higher than those in C group( P <0.05). The apoptotic rates of peripheral lymphocyte in A and B groups were evidently lower than that in S group ( P <0. 01). (2) The positive expression rate of MHC-II in monocyte was decreased sharply at 6 PSH, and it was 20% lower than that in C group (37. 2 +/- 2. 4% ) at 24 PSH. It then increased gradually, but it was significantly lower than that in A, B groups at 288 PSH (18. 8 +/-2. 8, P <0.01). (3) The plasma level of y-IFN in S group increased gradually from 6 PSH on, peaking at 24 PSH(440. 8 +/-25. 1 )ng/L,then decreasing gradually , and it reached the lowest level at 288 PSH (51.3 +/-37.0) ng/L. The IL-4 level in S group was increased gradually ,peaking at 288 PSH (78. 1+/-2. 8) ng/L. (4) There was negative correlation between the expression rate of MHC- II in S group and IL-4/gamma-IFN ratio in escharectomy groups during 72 - 288 PSH ( r = - 0. 96, P < 0. 05).

CONCLUSIONEacharectomy after scald can inhibit peripheral lymphocyte apoptosis, slow down the insertional tendency of IL-4/gamma-IFN , and ameliorate the antigen presentation function of monocytes. Moreover, escharectomy during shock stage can markedly promote the immune function of monocytes.