BDNF and myeloid sarcoma: In MS PBMC-derived neurotrophins could play a neuroprotective role directly, binding to trk receptors on neurons within the CNS and promoting their survival, or indirectly by interacting with the neurotrophin receptors on the immune cells, regulating their functions (proliferation, immunoglobulin production) and determining their survival or apoptosis [15,29,30].