X Figure: immediate recall Rey Complex Figure: delayed recall Wisconsin Card Sorting Test Wechsler Memory Scale-Revised General memory Delayed memory Verbal memory Visual memory AttentionControl 72.0611.1 124.3628.7 163.2634.6 263.9645.0 28.762.5 28.063.3 327.56108.CFS(2) 79.3613.7 125.1619.2 161.5631.2 260.8645.8 29.862.7 28.763.1 314.7641.CFS(+) 75.469.3 125.5630.7 187.4670.1 275.7627.0 28.763.3 27.862.7 338.26106.112.168.0 113.869.0 109.769.1 114.065.5 102.0614.114.569.4 115.0611.2 112.0610.6 114.765.2 100.5616.109.265.3 112.466.5 107.067.0 113.266.3 103.8613.Data are expressed as mean 6 SD. No significant differences were observed among control, CFS(2), and CFS(+) patients. doi:10.1371/journal.pone.0051515.t[11C](+)-3-MPB Binding in Brain of Autoantibody(+)ResultsFigure 1A shows the radioligand assay in serum samples collected on the PET experiment day. There were 5 positive patients (CFS(+)) whose serum autoantibody was higher than the cut-off value shown as a dashed line. In normal controls, there were no subjects with positive autoantibody against the mAChR. As shown in Table 1, fatigue scores, expressed by visual analogue scale, were similar between CFS(+) and CFS(2) patients (5.961.2 vs. 6.761.4, respectively). In all the 
neuropsychological assessments, there were no significant differences among the 3 groups (Table 2). Representative maps of the BPND of [11C](+)3-MPB using the Logan plot with reference regions are BI 78D3 site presented in Figure 1B. The BPND of [11C](+)3-MPB in each brain of CFS(+) patients were significantly lower than those in CFS(2) patients and control subjects (Fig. 1B, Table 3). Compared with controls, a 10?5 reduction of BPND was observed in CFS(+) patients (Table 3). AChE activity did not Pleuromutilin price differ among the 3 groups (Table 3). There were no significant differences in BPND between 23977191 CFS(2) patients and control subjects. There were no regions in which the BPND of [11C](+)3-MPB significantly correlated with any neuropsychological indices.DiscussionReduction of [11C](+)3-MPB binding was observed in CFS(+) patients who showed a higher level of serum autoantibody against the mAChR, compared with CFS(2) patients and normal controls. In contrast, the AChE activity was similar in subjects from the 3 groups. The indices of intelligence and cognitive function did not differ among the 3 groups, and these indices did not relate to [11C](+)3-MPB binding in this study. To 1326631 our knowledge, this is the first PET study to demonstrate a reduction of neurotransmitter receptor binding in brains of CFS patients with high levels of serum autoantibody. The present results suggest the possibility of the autoantibody interacting directly with 
the mAChR in the brain, although the autoantibody at this level did not affect cognitive function in CFS patients. The present finding supports the idea that penetration of the antibody into the brain resulted in impaired BBB function. This may be one possible mechanism by which the serum autoantibody could affect central mAChR function [57]. Although the precise mechanism of the production of the autoantibodies against the mAChR in the CFS brain is unclear, there are the following mechanisms based on an autoimmune reaction theory: 1) a viral infection of the brain tissue exposes the brain to self-antigen; and 2) an infection (not necessarily in the brain tissue) causes production of antibodies which, as a result of molecular mimicry, identify brain antigens as non-self and causeTable 3. Comparisons of [11.X Figure: immediate recall Rey Complex Figure: delayed recall Wisconsin Card Sorting Test Wechsler Memory Scale-Revised General memory Delayed memory Verbal memory Visual memory AttentionControl 72.0611.1 124.3628.7 163.2634.6 263.9645.0 28.762.5 28.063.3 327.56108.CFS(2) 79.3613.7 125.1619.2 161.5631.2 260.8645.8 29.862.7 28.763.1 314.7641.CFS(+) 75.469.3 125.5630.7 187.4670.1 275.7627.0 28.763.3 27.862.7 338.26106.112.168.0 113.869.0 109.769.1 114.065.5 102.0614.114.569.4 115.0611.2 112.0610.6 114.765.2 100.5616.109.265.3 112.466.5 107.067.0 113.266.3 103.8613.Data are expressed as mean 6 SD. No significant differences were observed among control, CFS(2), and CFS(+) patients. doi:10.1371/journal.pone.0051515.t[11C](+)-3-MPB Binding in Brain of Autoantibody(+)ResultsFigure 1A shows the radioligand assay in serum samples collected on the PET experiment day. There were 5 positive patients (CFS(+)) whose serum autoantibody was higher than the cut-off value shown as a dashed line. In normal controls, there were no subjects with positive autoantibody against the mAChR. As shown in Table 1, fatigue scores, expressed by visual analogue scale, were similar between CFS(+) and CFS(2) patients (5.961.2 vs. 6.761.4, respectively). In all the neuropsychological assessments, there were no significant differences among the 3 groups (Table 2). Representative maps of the BPND of [11C](+)3-MPB using the Logan plot with reference regions are presented in Figure 1B. The BPND of [11C](+)3-MPB in each brain of CFS(+) patients were significantly lower than those in CFS(2) patients and control subjects (Fig. 1B, Table 3). Compared with controls, a 10?5 reduction of BPND was observed in CFS(+) patients (Table 3). AChE activity did not differ among the 3 groups (Table 3). There were no significant differences in BPND between 23977191 CFS(2) patients and control subjects. There were no regions in which the BPND of [11C](+)3-MPB significantly correlated with any neuropsychological indices.DiscussionReduction of [11C](+)3-MPB binding was observed in CFS(+) patients who showed a higher level of serum autoantibody against the mAChR, compared with CFS(2) patients and normal controls. In contrast, the AChE activity was similar in subjects from the 3 groups. The indices of intelligence and cognitive function did not differ among the 3 groups, and these indices did not relate to [11C](+)3-MPB binding in this study. To 1326631 our knowledge, this is the first PET study to demonstrate a reduction of neurotransmitter receptor binding in brains of CFS patients with high levels of serum autoantibody. The present results suggest the possibility of the autoantibody interacting directly with the mAChR in the brain, although the autoantibody at this level did not affect cognitive function in CFS patients. The present finding supports the idea that penetration of the antibody into the brain resulted in impaired BBB function. This may be one possible mechanism by which the serum autoantibody could affect central mAChR function [57]. Although the precise mechanism of the production of the autoantibodies against the mAChR in the CFS brain is unclear, there are the following mechanisms based on an autoimmune reaction theory: 1) a viral infection of the brain tissue exposes the brain to self-antigen; and 2) an infection (not necessarily in the brain tissue) causes production of antibodies which, as a result of molecular mimicry, identify brain antigens as non-self and causeTable 3. Comparisons of [11.