3.3 Associations of serum concentration of CXCL13 in different disease activities in SLE patients, LN/non-LN patients, active/inactive LN patients, and high-avidity/low-avidity IgG ANAs
In our cohort of 97 SLE patients, a total of 20 patients (20.6%, 20/97) were diagnosed with no/mild disease activity SLE (0≤SLEDAI≤9), 44 patients (45.4%, 44/97) were diagnosed with moderate disease activity SLE (10≤SLEDAI≤14), and 33 patients (34.0%, 33/97) were diagnosed with severe disease activity SLE (SLEDAI≥15). A total of 54 patients (55.7%, 54/97) were diagnosed with LN, and 73 (75.3%, 73/97) patents were diagnosed with high-avidity IgG ANAs of SLE. Significantly higher serum CXCL13 levels were observed in SLE patients with severe disease activity [1023.077 (648.565-1768.138) pg/ml] among the no/mild disease activity [212.523 (30.229-297.550) pg/ml] and moderate disease activity SLE [341.845 (222.341-514.179) pg/ml] groups (p <0.001). (Figure 2a). We also found that the serum CXCL13 levels were significantly higher in the LN group [609.746 (338.472-1101.573) pg/ml] and active LN group [683.145 (399.065-1205.628) pg/ml] than in the non-LN group [279.310 (115.381-482.276) pg/ml] and inactive LN group [251.475 (125.930-315.340) pg/ml] (p <0.001) (Figure 2b, c). As in our previous study, we divided the SLE patients into a high-avidity IgG ANA group (RAI%≥40%) and a low-avidity IgG ANA group (RAI%<40%) according our detection assay. We found that the serum CXCL13 level was significantly higher in the high-avidity IgG ANA group [590.915 (280.092-1045.527) pg/ml] than in the low-avidity IgG ANA group [266.978 (117.615-408.526) pg/ml] (p <0.001) (Figure 2d).
3.4 Correlation analysis of the serum levels of CXCL13 with the SLEDAI, the RAI (relative avidity index) of HA IgG ANAs, the serum levels of anti-dsDNA, the ESR, and the C3 and C4 complements in SLE patients
In SLE patients, there was a correlation among the level of CXCL13, disease activities and laboratory results. The results showed that the concentration of CXCL13 was positively correlated with the SLEDAI score and RAI of HA IgG ANAs (r=0.7547, p <0.0001; r=0.5590,p <0.0001) (Figure 3a, b). The concentration of CXCL13 was positively related to the serum level of anti-dsDNA and ESR (r=0.4860, p <0.0001; r=0.3082, p =0.0021) (Figure 3c, d). Furthermore, the concentration of CXCL13 was negatively related and significantly decreased with serum C3 and C4 levels (r=-0.4605,p <0.0001; r=-0.5165, p <0.0001) (Figure 3e, f).