CD40 and vitamin B12 deficiency: In the gastrectomized rat model, vitamin B12 deficiency leads to increased spinal cord synthesis and increased cerebrospinal fluid (CSF) levels of two myelinotoxic cytokines, tumor necrosis factor-alpha (TNF-α) and soluble (s) CD40:sCD40 ligand dyad, and a myelinotoxic growth factor, nerve growth factor (NGF).