The immune system is a network of interacting cellular and soluble components. Its function is to distinguish entities within the body as \self\ or \nonself\ and to eliminate those that are nonself
Definition. A flow network is a directed graph G = (V, E) with two distinguished vertices: a source s and a sink t. Each edge (u, v) ∈ E has a nonnegative capacity c(u, v). If (u, v) ∉ E, then c(u, v) = 0