How does the specificity of lymphocytes for a single antigen molecule arise during their development?

The specificity of lymphocytes for a single antigen molecule arises through the clonal selection theory. During lymphocyte development, random genetic rearrangements create a diverse array of clones, each with a unique receptor specific to one antigen. Clones that react against self-antigens are eliminated, ensuring tolerance to self.

The clonal selection theory explains how lymphocytes develop specificity for a single antigen. Early in development, undifferentiated lymphocytes undergo genetic rearrangements, producing a vast array of clones, each with a unique receptor specific to one antigen. This diversity is achieved through the random recombination of gene segments that code for antigen receptors on B and T cells. Importantly, any clones that have receptors for self-antigens are eliminated through a process called clonal deletion, which is crucial for maintaining immune tolerance and preventing autoimmunity. Once mature, these lymphocytes populate lymphoid tissues, ready to respond to specific antigens they encounter.