APOE and atherosclerosis: Additionally, reactivity levels to heparin (in terms of OD values) in preimmune sera as well as in normal sera from age-matched apoE-/- mice were higher than those observed in previous studies, which is consistent with literature reports indicating an increase in serum IgG1 levels in advanced atherosclerosis due to a greater activation state of B lymphocytes (Rincón-Arévalo et al., 2016).