PRF1 and type 2 diabetes mellitus: Contradictorily, increased PD-1 proteins on the T cell subset that lacks CD28 molecules (popularly known as CD4+ CD28null T cells), which destabilizes the plaques with their in-built ability to release atheroma-deteriorating secretomes—IFN-γ, TNF-α, perforin and granzyme B—were increased among patients with aggressive atherosclerosis macrovascular disease with underlying type 2 diabetes mellitus (T2DM) comorbidity [56].