The immune system composed of cells that are sensitive to a series of surrounding factors and forming an integrated network. During the last decade a significant increase in the number of studies demonstrated that diet components released from adipocytes and metabolic pathways, affected the immune system and highly contributed to the human health. T-cells are significantly affected by nutrition. Decrease in glucose uptake and metabolism, cytokine synthesis, T-cell proliferation and survival in addition to decrease in circulating leptin level have been observed in cases of heavy malnutritions. It has also been shown that leptin represents an important link between nutrition and immunity. Additionally, the effects of diet components on epigenetic mechanisms were also found essential in regulation of the immunity-related genes. The microbiota has also been showen to be a significant factor in the formation and protection of the human immunity. In addition to supply adequate energy and protein requirements for immune system, supporting the immune system with specific nutrients (omega-3 fatty acids, vitamins, trace elements, flavonoids, etc.) is also important. Because they are also required to combat with local or systemic inflammation by strengthening the mucosal, cellular, and humoral immunity. Recently, the concept of immuno-nutrition has been applied with considerable interest. Nutritional Immunology, as a discipline, aims to understand nutritional factors influencing on immune responses.