What is the Difference Between Central and Peripheral Tolerance?

The difference between central and peripheral tolerance lies in the location and mechanisms involved in the induction of tolerance in the immune system. Immune tolerance is critical to prevent the development of autoimmune and inflammatory diseases. There are two main types of tolerance:

1. Central Tolerance: This type of tolerance occurs in the thymus and bone marrow, where T and B cells are educated. Central tolerance prevents the maturation and egress of autoreactive immune cells, for example, via clonal deletion of T cells in the thymus. Most autoreactive B cells are deleted in the bone marrow.
2. Peripheral Tolerance: This type of tolerance takes place in peripheral lymphoid organs and tissues, such as the spleen and lymph nodes. Peripheral tolerance is essential because not all antigens that T cells need to be tolerant of are expressed in the thymus, and thus central tolerance mechanisms alone are insufficient. Mechanisms of peripheral tolerance include:

• Clonal anergy: This occurs when T cells are activated in the absence of co-stimulation, leading to an unresponsive state.
• Suppression by regulatory T cells (Tregs): Tregs can suppress the function of self-reactive T cells and prevent them from causing damage in the periphery.

In summary, central tolerance is associated with the deletion of autoreactive cells in the thymus and bone marrow, while peripheral tolerance involves various mechanisms that act on mature circulating T cells to restrain their numbers and/or function. Both types of tolerance are crucial for maintaining immune homeostasis and preventing autoimmune and inflammatory diseases.

Comparative Table: Central vs Peripheral Tolerance

Central and peripheral tolerance are two types of immune tolerance that help the immune system discriminate between self and non-self antigens. Here is a table comparing the differences between central and peripheral tolerance:

In summary, central tolerance is the primary mechanism that helps the immune system discriminate self from non-self, occurring in the thymus and bone marrow. It operates on developing T and B lymphocytes that are reactive to self, mainly through deletion of self-reactive lymphocytes and production of Tregs. On the other hand, peripheral tolerance occurs in the peripheral tissues and lymph nodes, operating on self-reactive T and B lymphocytes that have escaped central tolerance. It functions through anergy, ignorance, or deletion of self-reactive lymphocytes and expansion of Tregs.