BBB can be broken centripetally (the most normal) or centrifugally. Several possible biochemical disrupters were proposed. Some hypotheses about how the BBB is compromised revolve around the presence of compounds in the blood that could interact with vessels only in the NAWM areas. The permeability of two cytokines, Interleukin 15 and LPS, may be involved in BBB breakdown. Breakdown is responsible for monocyte infiltration and inflammation in the brain. Monocyte migration and LFA-1-mediated attachment to brain microvascular endothelia is regulated by SDF-1alpha through Lyn kinase.