3.1. General clinical characteristics
The baseline characteristics of the patients with MG are shown in Table 1.
3.2. Expression of TRAF6 in MG patients
In general, the TRAF6 expression levels in CD19+ B cells and CD19+CD27+ memory B cells were both significantly higher in MG patients than in HCs (CD19+ B cells: HCs: 0.89 (0.36, 1.45), MG patients: 1.94 (1.018, 3.773), p < 0.01; CD19+CD27+ memory B cells: HCs: 0.27 (0.16, 1.57), MG: 2.25 (0.77, 4.42), p < 0.01) (Figure 1A, B).
Table 1 General clinical characteristics
|
MG (n=89)
|
HC (n=43)
|
Age (mean±SD)
|
58.34±14.99
|
55.72±19.51
|
Sex (male/female)
|
44/45
|
27/16
|
Onset age
|
55.36±15.20
|
|
EOMG
|
28/89
|
|
LOMG
|
61/89
|
|
AChR-Ab(+)
|
81/89
|
|
MuSK-Ab(+)
|
1/89
|
|
AChR-Ab/MuSK-Ab (-)
|
7/89
|
|
OMG
|
38/89
|
|
GMG
|
51/89
|
|
Thymoma
|
22/89
|
|
Thymic hyperplasia
|
3/89
|
|
Before treatment
|
42/89
|
|
MGFA-I
|
14/42
|
|
MGFA-II
|
10/42
|
|
MGFA-III
|
14/42
|
|
MGFA-IV
|
3/42
|
|
MGFA-V
|
0/42
|
|
MMS
|
47/89
|
|
Immunotherapy
|
|
|
Tacrolimus only
|
13/89
|
|
Corticosteroid only
|
13/89
|
|
Azathioprine only
|
1/89
|
|
Cyclophosphamide only
|
1/89
|
|
Tacrolimus and corticosteroid
|
6/89
|
|
Azathioprine and corticosteroid
|
2/89
|
|
Abbreviations:
MG: myasthenia gravis, HC: healthy control, n: number, EMOG: early-onset myasthenia gravis, LOMG: late-onset myasthenia gravis, AChR-Ab: Acetylcholine receptor-specific antibody, MuSK-Ab: Muscle-specific kinase-specific antibody, OMG: ocular myasthenia gravis, GMG: generalized myasthenia gravis, MGFA: MG Foundation of America, MMS: minimal manifestation status.
We classified the patients into the OMG group and the GMG group according to the muscle involved, and we found a greater increase in CD19+CD27+ memory B cells in GMG patients than in OMG patients when compared to the level in healthy people (HCs: 1.41 (1.05, 2.64), OMG: 2.04 (1.34, 2.04), GMG: 2.74 (1.87 4.05), p=0.002, p = 0.02, respectively). The elevated TRAF6 expression in CD19+ B cells and CD19+CD27+ memory B cells in GMG patients was greater than that in the corresponding cells in OMG patients before treatment (CD19+ B cells: OMG: 1.76 (0.83, 3.26), GMG: 3.23 (1.51, 6.70), p = 0.03; CD19+CD27+ memory B cells: OMG: 1.94 (0.68, 3.38), GMG: 3.23 (1.61, 6.45), p = 0.03). TRAF6 expression in CD19+ B cells and CD19+CD27+ memory B cells was low, and there was no significant difference between OMG and GMG in the MMS state; however, the expression levels were still higher than those in healthy subjects (Figure 1).
Furthermore, the before-treatment patients were classified by the guidelines of the MG Foundation of America (MGFA). TRAF6 expression exhibited an increasing trend from type I to type IV, and the differences between type I and type III were statistically significant (CD19+ B cells: p = 0.018, CD19+CD27+ memory B cells: p = 0.015) (Figure 2A, B).
In our study, the positive rate of TRAF6 had no significant correlations with sex, age or onset age, and thymoma also had no influence on this rate.
3.3. Relationship between TRAF6 expression and MG-ADL score
We found that there was a significantly positive correlation between the TRAF6 expression level in CD19+ B cells and the ADL score in both OMG patients and GMG patients before treatment (OMG: p < 0.001, r = 0.89; GMG: p = 0.001, r = 0.59) (Figure 2C, D). The TRAF6 expression level in CD19+CD27+ memory B cells was also positively correlated with the ADL score in OMG and GMG patients before treatment (OMG: p = 0.001, r = 0.80; GMG: p = 0.048, r = 0.38) (Figure 2E, F).
3.4. Expression of TRAF6 before and after treatment
In the 11 MG patients who were followed, TRAF6 expression was significantly decreased in both CD19+ B cells and CD19+CD27+ memory B cells after treatment (CD19+ B cells: before treatment: 2.30 (1.44, 4.52), after treatment: 0.40 (0.19, 2.48), p = 0.03; CD19+CD27+ B cells: before treatment: 1.71 (0.75, 6.00), after treatment: 0.56 (0.23, 3.06), p < 0.01) (Figure 3).