The components of immune system are specific (adaptive immunity) and non-specific (innate immunity). Regardless of antigenic properties, the non-specific components function either as eliminators or barriers of wide range of pathogens. A person is born with innate immunity as the natural resistances, which has three kinds; anatomic mechanical and biochemical factors. The resistances are provided by innate immunity via various chemical, cellular and physical approaches. The colonization, entry and spread of microorganisms can be prevented by innate immunity. Two main sub-divided types of adaptive immunity are humeral and cellular. Active immunity resulting from the development of antibodies in response to the presence of an antigen is a long-term and acquired immunity. This review article summarizes some important potential mechanisms in innate immune system. The host renal tract which has been investigated from many aspects of the pathogenesis of urinary tract infection (UTI) are still poorly defined and require a better understanding of the pathophysiology immune system.