Question

At the molecular level, why would Dendritic cells choose to convery antigen "tolerance" versus antigen immunity?

Answer 1

• Dendritic cells are antigen presenting cells of immune system derived from bone marrow. They process and present antigen to T-cells.
• They play an important role in both innate and adaptive immunity. They also involved in inducing and maintaining immune tolerance in steady state. Immune tolerance is the condition where there is no response from the immune system on substances that induce immunity. This prevent the autoimmune disorders by differentiating self and non-self antigens.
• Most of the dendritic cells in the lymphoid organs are in the state of immature or semi-mature. These present self antigens to T-cells inorder to maintain the tolerance. During inflammatory conditions dendrictic cells get matured and induce innate or adaptive immune response based on the type of antigen.
• Dendritic cells continuously present the self antigens in the absence of activating cytokines along with or without costimulation.
• Mature dendritic cells detect and recognize the pathogen with the help of pattern recognition receptors (PRR), secrete cytokines and present antigen to the T-cells in the lymphoid organ. In the same way immature dendritic cells present the antigen but in the absence of pathogen. If the T-cell bind to the self-MHC molecules carrying self antigen, they will be phagocytosed.
• When the dendritic cells encounter pathogen associated molecular patterns (PAMPs), they get stimulated to become a mature cells by changing its phagocytic function to antigen presenting function.