Recent epidemiological studies in France showed a high prevalence of obesity (14.5%) and its strong increase in the last 20 years. Among the many complications associated with obesity, liver complications (steatosis and steatohepatitis [NASH]) are among the most common. Semaphorins were described in the early 1990. More than 20 types of these proteins have been reported to date. These proteins were used for neural development. Since many functions have also been described. The semaphorins are involved in numerous physiological or physiopathological processes (cardiac morphogenesis, vascular growth, tumor progression), the regulation of immune cells and liver fibrosis. Preliminary studies have allowed to show that dendritic cells infiltrate adipose tissue and initiate the activation of T cells and inflammation. Immune semaphorin are new players in the regulation of inflammation and immune reactions.