Affinity purified anti-citrullinated protein/peptide antibodies target antigens expressed in the rheumatoid joint

Table 2 ACPA IgG responses (AU/mL) in 10 plasma and 11 synovial fluid samples “pre” and “post” CCP2 affinity column purification

Plasma	CCP		CEP-1		Cit-vim		Cit-fib		Cit-C1
Plasma	Pre	Post	Pre	Post	Pre	Post	Pre	Post	Pre	Post
RA 1	>3,200	>3,200	142	254	<10	45	17	417	17	122
RA 2	505	>3,200	104	1,207	<10	101	18	92	<10	20
RA 3	>3,200	>3,200	44	225	18	59	101	518	333	333
RA 4	>3,200	>3,200	97	1,052	30	65	33	79	77	195
RA 5	>3,200	>3,200	24	30	21	35	104	139	114	172
RA 6	>3,200	>3,200	13	43	30	70	18	36	<10	<10
RA 7	>3,200	>3,200	140	69	107	348	282	155	170	86
RA 8	>3,200	>3,200	11	15	<10	27	42	168	17	26
RA 9	763	>3,200	17	135	<10	59	<10	79	73	222
RA 10	1,151	>3,200	<10	24	<10	47	<10	92	18	38
Median	3,200	3,200	34	102	9	59	25.5	115.5	45.5	104
Synovial fluid	CCP		CEP-1		Cit-vim		Cit-fib		Cit-C1
Synovial fluid	Pre	Post	Pre	Post	Pre	Post	Pre	Post	Pre	Post
RA 11	2,447	>3,200	173	447	31	14	28	163	<10	<10
RA 12	311	1,780	<10	117	15	131	<10	156	<10	<10
RA 13	596	>3,200	15	1,339	19	32	<10	34	<10	185
RA 14	1,196	>3,200	22	109	<10	<10	<10	152	30	18
RA 15	508	>3,200	67	183	<10	191	<10	253	<10	200
RA 16	435	>3,200	16	46	<10	40	<10	<10	<10	111
RA 17	378	1,311	51	610	<10	167	<10	97	<10	44
RA 18	592	1,282	688	900	<10	17	<10	17	<10	48
RA 19	1,084	>3,200	85	339	23	115	17	187	19	62
RA 20	515	1,537	67	1,271	<10	17	<10	21	<10	80
RA 21	566	897	101	900	<10	113	<10	80	<10	146
Median	566	3,200	67^a	447^a	0	40	0	97	0	62

“Pre” samples were tested at a dilution of 1:100, and “Post” samples were tested at 10 μg/mL. Cutoffs for positivity: 25 AU/mL (CCP) and 10 AU/mL (CEP-1, Cit-vim, Cit-fib, and Cit-C1). ^aAnti-CEP-1 IgG levels in synovial fluid were significantly higher than the other anti-citrullinated protein/peptide antibody (ACPA) levels (P <0.01). CCP, cyclic citrullinated peptide; CEP-1, citrullinated α-enolase peptide 1 (amino acid 5-21); Cit-C1, citrullinated triple helical peptide/epitope on collagen type II (amino acid 359-369); Cit-fib, citrullinated fibrinogen peptide (β-chain, amino acid 36-52); Cit-vim, citrullinated vimentin peptide (amino acid 60-75); IgG, immunoglobulin G; RA, rheumatoid arthritis.

ISSN: 1478-6362