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Objective The aim was to evaluate whether T cell subsets and the lipid profile could be linked to the cardioprotective effect of IgM anti-phosphorylcholine (PC) antibodies in SLE. Methods Anti-PC antibodies were quantified by ELISA in 197 patients and 99 controls and analysed in relationship to clinical features, treatments and serum lipids. Carotid atheromatosis was evaluated by ultrasonography; Th1, Th17, Treg and CD4+CD28null cells by flow cytometry; and cytokine serum levels by immunoassays, in a subgroup of 120 SLE patients and 33 controls. Results IgM anti-PC serum levels were reduced in SLE patients compared with controls (P < 0.001) and were associated with age (β= −0.252; P = 0.002), high-density lipoprotein (HDL; β = 0.271; P = 0.001), low-density lipoprotein (LDL; β= −0.192; P = 0.017) and glucocorticoid treatment (β= −0.201; P = 0.012), whereas the IgG-to-IgM anti-PC ratio was increased (P = 0.007) and associated with age (β = 0.194; P = 0.028) and SLEDAI (β = 0.250; P = 0.005). Also, patients with clinical or subclinical cardiovascular disease exhibited reduced IgM anti-PC levels compared with their cardiovascular disease-free counterparts, regardless of glucocorticoid usage (P = 0.001). CD4+CD28null and Th17 cells were increased in SLE patients compared with controls (P < 0.01) and correlated inversely with IgM anti-PC levels. These associations were observed in patients displaying high triglyceride or low HDL levels, even after adjusting for clinical parameters and treatments (CD4+CD28null: β = −0.455, P = 0.001; Th17: β= −0.280, P = 0.035), but not in those with a normal lipid profile. High triglyceride and low HDL profiles were related to low IgM anti-PC and Treg levels, respectively, whereas both lipid profiles were associated with inflammatory markers and cytokines. Conclusion The present study provides evidence for an association of IgM anti-PC antibodies with pro-atherogenic T cell subsets in SLE, with a high triglyceride/low HDL lipid profile playing a facilitating major role. [ABSTRACT FROM AUTHOR]