Clonal deletion

Clonal Deletion

Clonal deletion is a process by which B cells and T cells are deactivated in the immune system to prevent them from attacking the body's own cells, thus preventing autoimmune diseases. This process is a crucial part of the immune system's ability to distinguish between self and non-self.

Overview

During the development of lymphocytes, cells undergo a selection process to ensure that they do not react with self-antigens. This process, known as clonal deletion, is a form of immune tolerance. It occurs in the thymus for T cells and in the bone marrow for B cells.

Mechanism

In the thymus, developing T cells, or thymocytes, that bind too strongly to self-antigens presented by major histocompatibility complex (MHC) molecules are induced to undergo apoptosis, or programmed cell death. This process is known as negative selection and results in the deletion of self-reactive clones.

In the bone marrow, developing B cells that bind to self-antigens are either induced to undergo apoptosis or undergo receptor editing, a process in which the B cell rearranges its immunoglobulin genes in an attempt to produce a receptor that does not react with self.

Significance

Clonal deletion is a crucial mechanism for preventing the development of autoimmune diseases, which occur when the immune system mistakenly attacks the body's own cells. However, it is not 100% efficient, and some self-reactive lymphocytes may escape deletion and become activated, leading to autoimmunity.

See also

• Central tolerance
• Peripheral tolerance
• Autoimmune disease
• Immunology