Abstract： Objective To observe effects of hyperbaric oxygen on the changes in proteolipid protein (PLP), PLP antigen and antibody in serum in rats with acute carbon monoxide poisoning(ACOP) and to explore the role of the immune system in ACOP and also the mechanism that might be involved in. Methods Two hundred and two rats were randomly divided into 3 groups: the carbon monoxide (CO) group, the HBO group and the norrnobaric oxygen (NBO) group. The rat model of ACOP was established with static inhalation of CO. Abdominal aorta blood was collected before poisoning, the moment immediately after poisoning, 100 min, 3rd, 7th, 10th and 20th days after poisoning. Then, levels of PLP antigen and PLP antibody were measured with ELISA. Results For the CO group measured immediately after poisoning in the HBO group and NBO group, the levels of PLP antigen and antibody elevated, when they were compared with those before poisoning(P ＜0.05). The level of PLP antigen at 100 min in the HBO group was lower than that of the CO group (P ＜ 0.05 ). The levels of PLP antibody in the HBO group were lower than those of the CO group on 3rd and 7th days( P ＜ 0. 05 ). The levels of PLP antibody in the HBO group were lower than those of the NBO group on 3rd and 10th days(P ＜0.05); The levels of PLP antibody in the NBO group were lower than those in the CO group on 7th and 20th days ( P ＜ 0.05 ). Conclusions Following acute carbon monoxide poisoning, levels of PLP antigen and PLP antibody increased in serum, which initiated impairment of myelin and an adaptive immunological response. Regular HBO and NBO treatment could alleviate lesion to the myelin following CO poisoning, and HBO treatment was more effective than NBO treatment.