TAK patients and HC
Thirty-two consecutive TAK patients and 30 HC with similar mean age (45.6 ± 13.7 years vs. 44.1 ± 10.8 years, p = 0.651) and female/male ratio (30/32 vs. 28/30, p = 0.947) were included in the study. Table 1 describes the disease features and therapy of TAK patients. Type V was the most frequent angiographic type observed in TAK patients followed by type I. Twenty-seven (84.4%) patients received therapy for TAK including immunosuppressive agents or biological agents. TNF inhibitors and tocilizumab were the biologic agents prescribed (Table 1). Twelve TAK patients (37.5%) used prednisone with a median daily dose of 6.3mg (2.5-20.0).
Monocyte subsets in TAK patients and HC
TAK patients presented a higher number of circulating intermediate monocytes compared to HC [25.0 cells x 106/L (16.6-52.0) vs. 17.2 cells x 106/L (9.2-25.3); p = 0.014]. However, no significant differences were observed between TAK patients and HC regarding total monocytes [493.1 cells x 106/L (313.5-976.7) vs. 461.3 cells x 106/L (314.0-544.1); p = 0.185], classical monocytes [453.1 cells x 106/L (269.5-819.7) vs. 420.7 cells x 106/L (278.0-506.4); p = 0.200] and non-classical monocytes [20.8 cells x 106/L (9.7-49.3) vs. 14.2 (6.5-28.3); p = 0.125] (Figure 2). In addition, no differences were observed between TAK patients and HC for the percentage of the classical [88.5% (83.7-91.4) vs. 90.9% (87.5-94.7); p = 0.111], intermediate [5.8% (4.1-7.4) vs. 3.7% (2.8-6.7); p = 0.066], and non-classical subsets [4.8% (3.5-7.5) vs. 3.4% (1.4-6.8); p = 0.149] (Figure 2).
Monocyte subsets and disease activity in TAK
The comparisons among active TAK, TAK in remission and HC yielded significant differences regarding the number of total monocytes [976.1 cellsx106/L (495.0-2,438.4) vs. 465.8 cellsx106/L (283.4-677.0) vs. 461.3 cellsx106/L (314.0-544.1); p = 0.025], classical monocytes [818.8 cellsx106/L (451.2-2,004.9) vs. 404.0 cellsx106/L (257.4-604.0) vs. 420.6 cellsx106/L (278.0-506.4); p = 0.022] and intermediate monocytes [55.4 cellsx106/L (27.5-162.2) vs. 20.7 cellsx106/L (15.7-33.8) vs. 17.2 cellsx106/L (9.2-25.3); p = 0.003]. However, no differences were found between active TAK, TAK in remission and HC regarding the number of non-classical monocytes [43.3 cellsx106/L (18.0-259.9) vs. 18.3 cellsx106/L (8.4-40.3) vs. 14.2 cellsx106/L (6.5-28.3); p = 0.089] in the peripheral blood, respectively. The percentage of the classical [86.2% (78.6-89.6) vs. 89.1% (84.5-91.9) vs. 90.9% (87.5-94.7); p = 0.171], intermediate [6.5% (3.7-8.1) vs. 5.5% (4.1-7.0) vs. 3.7% (2.8-6.7); p = 0.154], and non-classical subsets [6.3% (3.5-11.4) vs. 5.5% (2.6-7.2) vs. 3.7% (2.8-6.7); p = 0.265] was not different among these three groups (Figure 3).
In the post hoc analyses, the main differences regarding the number of monocytes in the peripheral blood were found between TAK patients with active disease and HC for total monocytes (p = 0.005), classical monocytes (p = 0.005), and intermediate monocytes (p = 0.001). However, differences between TAK patients with active disease and those in remission were not significant according to Bonferroni’s correction (i.e., p < 0.016) for total monocytes (p = 0.029), classical (p = 0.023), and intermediate monocytes (p = 0.019) in the peripheral blood. In addition, TAK patients with active disease and those in remission had similar numbers of total monocytes and their subsets (p > 0.05) (Figure 3). Longitudinal analysis of monocytes in TAK
Four TAK patients with active disease were reassessed for monocytes subsets in the peripheral blood when achieving remission at a median of 14.5 months (11.3-18.5) after the first assessment. Despite the low number of patients assessed longitudinally, an apparent decrease in the median number of cells in the peripheral blood was observed between active disease and remission in TAK in paired analyses of total monocytes [1,972.0 cells x 106/L (491.0-4,986.0) vs. 411.0 cells x 106/L (334.7-545.0)], classical monocytes [1,643.0 cells x 106/L (423.9-3,743.0) vs. 360.9 cells x 106/L (271.4-462.6)], intermediate monocytes [118.9 cells x 106/L (33.0-206.3) vs. 20.7 cells x 106/L (14.6-22.2)], and non-classical monocytes [180.5 cells x 106/L (30.5-1,026.0) vs. 40.6 cells x 106/L (25.0-61.4)] from active disease to remission, respectively.
Serum chemokines in TAK patients and HC
Significant differences among TAK patients with active disease, TAK patients in remission and HC were found for serum CCL22 (2030.5 ± 982.5 pg/mL vs. 1222.3 ± 552.6 pg/mL vs. 1390.6 ± 410.9 pg/mL; p = 0.011), serum CCL3 [5.7 pg/mL (4.6-11.2) vs. 6.3 pg/mL (5.0-7.5) vs. 9.3 pg/mL (5.7-14.7); p = 0.033] and serum CCL4 levels (36.1 ± 15.1 pg/mL vs. 37.9 ± 17.9 pg/mL vs. 51.3 ± 20.4 pg/mL; p = 0.023], respectively (Figure 4).
The post hoc analyses with the Tukey’s test showed higher median serum CCL22 in TAK patients with active disease compared to patients in remission (p = 0.008), and between active disease and HC (p = 0.048). Serum levels of CCL3 and CCL4 were lower in patients in remission than HC (p = 0.010 and p = 0.028, respectively). No differences were found for CCL3 and CCL4 levels between active TAK and TAK in remission (p = 0.979 and p = 0.978, respectively) or between active TAK and HC (p = 0.219 and p = 0.231, respectively) (Figure 4).
No significant differences were found among active TAK, TAK in remission and HC for serum concentrations of CX3CL1, CXCL10, CCL2, CCL5 and CCL7, respectively (Supplementary Table S1).
Correlations between monocyte subsets and serum chemokines with ITAS2010 and acute phase reactants in TAK
No correlations were found between total monocytes and monocyte subsets counts in the peripheral blood with erythrocyte sedimentation rate (ESR), serum C-reactive protein (CRP) or ITAS2010 score (Supplementary Table S2). The analysis of correlations between serum chemokine levels and acute phase reactants or ITAS2010 score yielded only a significant negative correlation between serum CCL2 levels and ITAS2010 score (rho = -0.611; p = 0.046). No significant correlations were observed between serum levels of other chemokines and ESR, serum CRP or ITAS2010 score (Supplementary Table S3).
Interactions between monocyte subsets and chemokines in TAK patients
Serum CCL4 levels were significantly correlated with the total number of monocytes (Rho: 0.489; p = 0.005), as well as, with classical and intermediate monocytes (Rho: 0.448; p = 0.010 and Rho: 0.412; p = 0.019, respectively). CCL7 was also significantly correlated with the number of non-classical monocytes in the peripheral blood (Rho: 0.360; p = 0.043). No other correlations were found between other serum chemokine levels and total monocytes or monocyte subsets in the peripheral blood from TAK patients (Supplementary Table S4).
The impact of therapy on monocyte subsets and serum chemokines
Firstly, we analyzed the effect of prednisone use and its daily dose on monocyte subsets and circulating chemokines. TAK patients using prednisone dose ≥ 5mg were compared to those on prednisone < 5mg/day or no prednisone. Daily prednisone ≥ 5mg was associated with a lower percentage of non-classical monocytes compared to daily prednisone < 5mg [3.7% (1.3-4.1) vs. 6.9% (3.9-8.5), p = 0.011]. No other significant differences were observed in the absolute numbers and percentages of monocyte subsets in the peripheral blood regarding prednisone use in TAK patients. When relations between prednisone use and serum chemokines were analyzed, TAK patients on a prednisone daily dose ≥ 5mg presented lower serum CXCL10 levels than those using < 5mg/day. No differences were observed regarding prednisone use and serum levels of other chemokines in TAK patients (Table 2). The prednisone daily dose also had a strong negative correlation with the percentage of non-classical monocytes (rho: -0,796; p = 0.002). (Supplementary Table S5). Correlations between daily prednisone dose and serum chemokines yielded no significant results (Supplementary Table S5).
The impact of immunosuppressive and biological agents on monocyte subsets and serum chemokine levels was also analyzed in TAK patients. Despite the lower number of total monocytes and classical monocytes in the peripheral blood in TAK patients on immunosuppressive agents, the comparison with those on biological agents and no therapy in the post hoc analyses yielded no significant results according to Bonferroni’s correction (i.e., p > 0.016) (Table 3). No other significant differences were observed for monocyte subsets and serum chemokine levels regarding therapy for TAK (Table 3).