ABCG1 and infection: In addition, the expression of the following BBB specific transporter markers were induced during infection: TFRC (related to iron metabolism), ABCG1 (cholesterol homeostasis), SLC15A3 (proton oligopeptide co-transporters), SLC7A5 (cationic amino acid transporters and the glycoprotein-associated amino acid transporters), ABCC3 (multidrug resistance associated protein 3) and ABCC5 (multidrug resistance associated protein 5).