The innate lymphoid cel ls ( ILC) are a group of lymphocytes that constitute part of innate immunity. The ILC do not have either TCR (T-cell receptor) or BCR (B-cell receptor).The ILC-1, ILC-2 and ILC-3 form three groups of the innate lymphoid cell family while each of these groups have an individual cytokine production profile and a different function. The first response to an infection or tissue damage, and the regulation of commensal microorganisms are the main functions of the ILCs. However, autoimmune and allergic diseases such as allergic asthma, Crohn disease and psoriaasis could be the result of excessive stimulation of innate lymphoid cells. The understanding of the function of the ILCs has improved our knowledge of many chronic diseases in general and will most probably help us find new treatment options in the future.