*4.2.5 Lipid metabolism*

FAs and cholesterol, important building materials for cell membranes, are energydense substrates, and are required for post-translational modifications, thereby modulating T-cell proliferation and differentiation. This ability to guide posttranslational modifications (by serving as ligands for several transcription factors) varies with the length of their carbon atom chains (short-chain FAs with less than 6 carbon atoms *vs*. long-chain FAs with more than 12 carbon atoms) and their degree of saturation (polyunsaturated fatty acids, PUFA *vs*. saturated fatty acids, SFA/monounsaturated fatty acids, MUFA).
