THU0230 IGG1 ANTIBODIES AGAINST PHOSPHORYLCHOLINE ARE NEGATIVELY ASSOCIATED WITH DISEASE ACTIVITY, DISEASE DAMAGE, CARDIOVASCULAR DISEASE AND ATHEROSCLEROSIS IN SLE: POTENTIAL UNDERLYING MECHANISMS.
Authors: D. Thiagarajan, R. Fiskesund, J. Steen, M. Rahman, S. Lundström, J. Frostegård
Journal: Annals of the Rheumatic Diseases (2020)

Background: Phosphorylcholine (PC) is an important component in cellular membranes and in lipoproteins that is exposed and recognized by the immune system, when cells undergo apoptosis or lipoproteins like LDL undergo oxidation. PC is also exposed in some microorganisms including nematodes and bacteria (non-self). We reported that IgM anti-PC is associated with protection in atherosclerosis, SLE, RA and other chronic inflammatory conditions. 1 We also reported potential underlying protective mechanisms: 1: increase in clearance of human dead cells, 2 2: inhibition of uptake of oxLDL in macrophages, 3: inhibition of cell death. 1 4: anti-inflammatory; 5: promotion of polarization of T regulatory cells in SLE-patients´ T cells from a low level and also in plaque T cells. 3 We generated in-house fully human IgG1 anti-PC clones for experimental studies to study anti-PC properties in humans. In contrast to mice, anti-PC are not germ-line encoded with a dominant clone. 4 Objectives: We here study IgG1 and IgG2 anti-PC, with focus on atherosclerosis and SLE and properties of fully human IgG1 clones, in relation to SLE. Methods: We determined anti-PC by ELISA in 116 SLE-patients and 110 age- and sex-matched controls. For functional studies, we used three in-house generated, fully human monoclonal IgG1 anti-PC (A01, D05, E01). Apoptosis was induced in Jurkat T-cells and pre-incubated with A01, D05, E01 or isotype control IgG1 and effects on efferocytosis by human macrophages studied. Anti-PC peptide/protein characterization was determined using a proteomics de novo sequencing approach. Results: IgG1 but not IgG2 anti-PC levels were higher among SLE patients (p=0.02). IgG1 anti-PC was negatively associated with SLICC and SLEDAI (OR: 2,978 CI: 0.876-10.098, OR: 5.108 CI 1.3 20.067 respectively) and negatively associated with CVD, atherosclerotic plaques and echolucent (potentially vulnerable plaques) but the association for the two former was not significant after controlling for confounders. D05 had maximum effect on macrophage efferocytosis efficiency, followed by A01 and E01. The monoclonal antibodies showed differential binding specificity to PC and PC associated neo-epitopes. Peptide analysis showed difference in the CDR3 region of the three anti-PC IgG1 clones which are crucial for recognition of PC on apoptotic cell surface and other neo-epitopes. Conclusion: Anti-PC IgG1 is negatively associated with disease activity, and disease damage in SLE, but the negative association with CVD is also dependent on confounding risk factors. One potential underlying mechanism could be increased clearance of dead cells. References: [1]Frostegard J. Immunity, atherosclerosis and cardiovascular disease. BMC Med . 2013;11:117. [2]Rahman M, Sing S, Golabkesh Z, Fiskesund R, Gustafsson T, Jogestrand T, Frostegard AG, Hafstrom I, Liu A and Frostegard J. IgM antibodies against malondialdehyde and phosphorylcholine are together strong protection markers for atherosclerosis in systemic lupus erythematosus: Regulation and underlying mechanisms. Clin Immunol . 2016;166-167:27-37. [3]Sun J, Lundstrom SL, Zhang B, Zubarev RA, Steuer J, Gillgren P, Rahman M, Ajeganova S, Liu A and Frostegard J. IgM antibodies against phosphorylcholine promote polarization of T regulatory cells from patients with atherosclerotic plaques, systemic lupus erythematosus and healthy donors. Atherosclerosis . 2018;268:36-48. [4]Fiskesund R, Steen J, Amara K, Murray F, Szwajda A, Liu A, Douagi I, Malmstrom V and Frostegard J. Naturally occurring human phosphorylcholine antibodies are predominantly products of affinity-matured B cells in the adult. J Immunol . 2014;192:4551-9. Disclosure of Interests: : Divya Thiagarajan: None declared, Roland Fiskesund: None declared, Johanna Steen: None declared, Mizanur Rahman: None declared, Susanna Lundström: None declared, Johan Frostegård Grant/research support from: Unconditional competitive grant from Amgen, related only to PCSK9, not the topic of this abstract