CXCL13 and human African trypanosomiasis: The most interesting cytokines and chemokines used for staging sleeping sickness are IL-10, IL-6, IL-1β, CCL-3, CXCL-8, SLPI, Lipocalin 2, ICAM-1, VCAM, MMP-9, MMP-2, CXCL-10, and CXCL-13 [48, 49], which permit the activation and amplification of the immune response and allow leukocytes which are sequestered in the perivascular space to transmigrate across the basement membrane and the glial limitans to reach the brain parenchyma [50].