Table 1.
Relative concentration of specific ACPA, anti-CCP2 and circulating immune complexes (CIC) in sera and synovial fluids
| Sequence | Number of patients reacting in serum (%) | Serum median (mean) | SF median (mean) | P values (Wilcoxon) |
Compartment with highest level | Serum/ IgG median (mean) |
SF/ IgG median (mean) |
P values (Wilcoxon) |
Compartment with highest level | |
| Filaggrin 307–324 (CCP1) | HQCHQEST(cit)GRSRGRCGRGS (cyclic) | 55/77 (71) | 38.89 (233.82) | 17.07 (185.86) | 0.0005 | Serum | 3.16 (22.69) | 4.19 (36.59) | 0.0282 | SF |
| Vimentin 2–17 | ST(cit)SVSSSSY(cit)(cit)MFGG | 40/77 (52) | 2.7 (14.78) | −0.43 (19.40) | 0.9179 | 0.14 (1.27) | −0.11 (3.79) | 0.561 | ||
| Vimentin 60–75 | VYAT(cit)SSAV(cit)L(cit)SSVP | 48/77 (62) | 36.76 (195.93) | 11.5 (168.09) | 0.0575 | 2.63 (18.14) | 4.00 (36.36) | 0.0009 | SF | |
| Fibrinogen α36–50 | GP(cit)VVE(cit)HQSACKDS | 22/77 (29) | 0 (61.38) | 0 (53.56) | 0.1822 | 0 (4.67) | 0 (9.67) | 0.0355 | SF | |
| Fibrinogen α563–583 | HHPGIAEFPS(cit)GKSSSYSKQF | 47/77 (61) | 10.05 (107.30) | 6.48 (82.61) | 0.0378 | Serum | 1.02 (10.51) | 1.08 (18.02) | 0.0216 | SF |
| Fibrinogen α580–600 | SKQFTSSTSYN(cit)GDSTFESKS | 25/77 (32) | 0 (43.90) | 0 (27.70) | 0.1398 | 0 (4.65) | 0 (7.61) | 0.5338 | ||
| Fibrinogen α621–635 | (cit)GHAKS(cit)PV(cit)GIHTS | 36/77 (47) | 0 (121.15) | 0 (91.35) | 0.3756 | 0 (13.33) | 0 (20.48) | 0.0987 | ||
| Fibrinogen β36–52 | NEEGFFSA(cit)GHRPLDKK | 47/77 (61) | 14.38 (156.83) | 7.44 (132.73) | 0.039 | Serum | 1.33 (13.84) | 2.32 (27.04) | 0.0087 | SF |
| Fibrinogen β60–74 | (cit)PAPPPISGGGY(cit)A(cit) | 52/77 (68) | 17.7 (170.93) | 7.49 (156.08) | 0.0292 | Serum | 1.46 (14.62) | 2.40 (30.47) | 0.0005 | SF |
| Fibrinogen β62-81(Fib72) | APPPISGGGY(cit)ARPAKAAAT | 25/77 (32) | 0 (11.19) | 0 (7.09) | 0.9311 | 0 (1.16) | 0 (1.60) | 0.936 | ||
| Fibrinogen β62-81(Fib74) | APPPISGGGYRA(cit)PAKAAAT | 22/77 (29) | 0.55 (35.02) | 0.73 (32.12) | 0.2692 | 0.06 (2.76) | 0.11 (6.08) | 0.0305 | SF | |
| α-Enolase 5-21(CEP-1) | CKIHA(cit)EIFDS(cit)GNPTVEC (cyclic) | 49/77 (64) | 72.82 (263.44) | 32.4 (235.90) | 0.0183 | Serum | 7.85 (22.65) | 6.79 (55.09) | <0.0001 | SF |
| hnRNP 1 | (proprietary)* | 28/77 (36) | 9.79 (70.52) | 6.44 (53.49) | 0.0003 | Serum | 0.89 (6.06) | 1.72 (10.64) | <0.0001 | SF |
| hnRNP 5 | (proprietary)* | 49/77 (64) | 19.8 (134.97) | 9.14 (120.27) | 0.1191 | 1.67 (12.52) | 2.36 (26.61) | 0.0005 | SF | |
| hnRNP Z1 | (proprietary)* | 35/77 (45) | 0 (65.53) | 0.83 (56.09) | 0.4464 | 0 (6.47) | 0.25 (13.54) | 0.0283 | SF | |
| hnRNP Z2 | (proprietary)* | 46/77 (60) | 4.96 (128.27) | 6.21 (105.07) | 0.1726 | 0.43 (13.44) | 2.75 (24.81) | 0.0066 | SF | |
| hnRNP Bla26 | (proprietary)* | 41/77 (53) | 4.57 (45.95) | 0.81 (45.32) | 0.2491 | 0.43 (4.13) | 0.46 (8.74) | 0.005 | SF | |
| Histone4 14–34 | GAK(cit)H(cit)KVL(cit)DNIQGITKPAI | 32/77 (42) | 18.77 (109.76) | 11.64 (81.80) | <0.0001 | Serum | 1.66 (9.79) | 2.14 (15.51) | 0.0053 | SF |
| Histone4 31–50 | KPAI(cit)(cit)LA(cit)(cit)GGVK(cit)ISGLI | 47/77 (61) | 11.04 (101.92) | 4.79 (67.97) | 0.029 | Serum | 0.75 (10.42) | 1.36 (11.51) | 0.3402 | |
| Anti-CCP2 | – | 55/77 (71) | 132 (317.25) | 55 (153.99) | <0.0001 | Serum | 11.60 (29.44) | 10.48 (39.95) | 0.0053 | SF |
| CIC µg Eq/mL | – | – | 0.53 (12.35) | 0.27 (5.87) | 0.0252 | Serum | 0.042 (1.112) | 0.054 (0.914) | 0.5018 |
Values are shown both as arbitrary units in sera and SF, as well as after correction for total IgG levels in the corresponding serum or SF samples. Comparisons were performed with the Mann-Whitney U test; significant differences are depicted in bold. The second column details the sequences of the citrullinated peptides in the multiplex assay, using the single-letter amino acid code and ‘(cit)’ for citrulline. The not listed arginine-containing control peptides have identical sequences except that they contain arginine residues instead of citrulline.
*Peptides are derived from hnRNP A3. Available on request from KS; see authors’ details.
ACPA, anti-citrullinated protein/peptide antibodies; SF, synovial fluid.