A putative hematopoietic differentiation pathway for myeloid and lymphoid DC. Lymphoid DC have different properties (?tolerizing) from the myeloid DC, which is immunostimulatory in most circumstances. The surveillance tissue-based DC:LC in the skin, DC in the respiratory tract, gut, or other nonlymphoid tissues, migrate after exposure to infection, tissue damage/inflammation, or antigen (ie, danger signals) via the afferent lymphatics to the T-lymphocyte–dependent areas of the draining LN. It is possible that epithelial based CD1⁺ DC have an independent derivation from the stem cell. The ability of Mo and Mø to convert to DC in vivo has yet to be established.