Antigen-presenting dendritic cells (DCs) represent trace population of leukocytes that are widely distributed over the whole body. DCs are regarded as inducer of antigen-specific adaptive immune responses. However, various types of functions of DCs are now exposing. In the steady-state, DCs induce immunogenic tolerance to self antigens and harmless entities and thus maintain normal homeostasis. On the other hand, in presence of non-self and dangerous entities, DCs play a cardinal role in the induction of innate immunity by producing type-1 interferons. DCs are also essential for the development of antigen-specific B-lymphocytes and plasma cells. Infection, depletion and dysfunction of DCs have been reported from patients with chronic microbial infections. Impaired functions of DCs have also been shown from patients with autoimmune diseases and allergic diseases. Patients with cancers also have phenotypic and functional impairment of DCs. These observations inspired optimism of using DC-based therapy for treating different pathological conditions. DC-based therapies showed excellent therapeutic potential in animal model of human diseases. The efficacy of DC-based therapy has not been properly evaluated in patients with different diseases. However, some clinical trials indicate that administration of antigen-pulsed DCs might be safe and possibly effective. In this review, we would first provide a description about the nature and functions of DCs that have been taught from the laboratory benches. Next, we would discuss how the information taught in the laboratory benches has been applied in patient's bedsides.