Question

1a) What is Dendritic Cell Licensing?

b) What happens to the immune response if Dendritic Cell Licensing is removed (or knocked-out)?

Answer 1

Dendritic cells constitute only 0.2% of WBCs in the blood bit play an important role in nonspecific resistance. They are present in the skin and mucous membranes of the nose,lungs, and intestines where they readily contact invading pathogens, phagocytose and process antigens, and display foreign antigens on their surface.

CD8(+) T cells require CD4(+) T cell help for memory formation. Evidence suggests that such help can be antigen independent, challenging whether the 'licensing' of dendritic cells (DCs) by CD4(+) T cells is ever required for cytotoxic T lymphocyte (CTL) responses. We show here that help is essential for the generation of CTL immunity to herpes simplex virus 1 and that CD4(+) T cells mediate help in a cognate, antigen-specific way. We provide direct in vivo evidence for DC licensing by helper T cells and show that licensing is rapid and essential for the formation of effector and memory CTLs. In situations in which DCs are poorly licensed by pathogen-derived signals, our findings suggest that CTL immunity may be heavily dependent on cognate DC licensing.

Ans-2 When the dendritic cell begins to mature, it also starts moving, or migrating toward a lymph node. The lymph nodes contain large numbers of lymphocytes, another type of immune cell. Everyone probably remembers having enlarged lymph nodes in their neck when they had a sore throat. The lymph nodes are where the action is when it comes to the immune system. There are areas in the body that contain large numbers of lymph nodes. The neck, armpits, and groin areas all have clusters of nodes that lie close to the skin.
So the mature dendritic cell has migrated to the lymph node. There it comes in
contact with different kinds of lymphocytes. If it has matured properly, the co-
stimulatory molecules on its surface will help pass the tumor information along to the cytotoxic T lymphocytes, or CTLs. The CTLs are the body's main defense against tumor cells. When the right CTL comes in contact with the dendritic cell, it will become activated and begin to divide, effectively making an army of cloned soldiers ready to kill any cancerous or pre-cancerous cell.

The role of DCs in our immune system:

DCs (also known as accessory cells) process and present soluble antigens, in complex with either class I or class II major histocompatibility complex (MHC) molecules on their cell surface, to the B or T cells, which carry receptor molecules that recognize specific targets. DCs thus act as messengers between the innate immune system and the adaptive immune system.

DCs are present in trace numbers in most tissues and in a relatively immature state, especially in the blood. However, in the presence of inflammatory signals, they rapidly recognize foreign antigens and undergo maturation. Once activated, they migrate to the lymph nodes, where they interact with T and B cells to initiate an immune response.