Vitamin B1 (thiamin) is considered to be the oldest vitamin and in 1936 R.R. Williams and colleagues determined its chemical structure and were able to synthesize this vitamin. Vitamin B1 influences pro-apoptotic proteins, mitochondrial membrane potential, cytochrome C release, protein kinases, p38-MAPK, suppresses oxidative stress-induced NF-kappaB and has anti-inflammatory properties. Deficiency of vitamin B1 may cause beriberi, dysfunction of the nervous system, neuroinflammation, T cell infiltration, chemokine CCL2 activation, over expression of proinflammatory cytokines, such as IL-1, TNF, IL-6, and arachidonic acid products, and induces expression of CD40 by the microglia and CD40L by astrocytes which provoke the death of neurons. Here we report the relationship between vitamin B complex and immunity.