Most important antigen presenting cells in human?

Ans. c (Langerhan's cells/histiocytes). (Ref. Robbins, Pathology, 7th, 199, 1228)# Macrophages have role in inflammation and induction and effector phase of immune response.# Dendritic cells are important antigen presenting cells for initiating primary immune responses against protein ags.# Features which contribute to their function are location at right place to capture ags (under epithelia, in interstitia), expression of receptors for capturing and responding to microbes (TLRs and mannose receptors) and expression of same chemokine receptors as do naive T-and immature dendritic cells within epidermis are Langerhan's cells.Cell TypeMajor Role in Innate ImmunityMajor Role in Adaptive ImmunityPlasmacytoid dendritic cells (DCs) of lymphoid lineageProduce large amounts of IFN-alpha which has antitumor and antiviral activity, and are found in T cell zones of lymphoid organs; they circulate in blood.IFN-alpha is a potent activator of macrophage and mature DCs to phagocytose invading pathogens and present pathogen antigens to T and B cellsMyeloid dendritic cells are of two types; Interstitial and Langerhans-derived- Interstitial DCs are strong producers of IL-12 and IL-10 and are located in T cell zones of lymphoid organs, circulate in blood, and are present in the interstices of the lung, heart, and kidney;- Langerhans DCs are strong producers of IL-12; are located in- T cell zones of lymph nodes,- Skin epithelia, and- Thymic medulla;- and circulate in bloodInterstitial DCs are potent activators of macrophages and mature DCs to phagocytose invading pathogens and present pathogen antigens to T and B ceils