AICDA encodes a RNA-editing deaminase that is a member of the cytidine deaminase family. The protein is involved in somatic hypermutation, gene conversion, and class-switch recombination of immunoglobulin genes. Defects in this gene are the cause of autosomal recessive hyper-IgM immunodeficiency syndrome type 2 (HIGM2).

Class switch recombination (CSR) is a region-specific DNA recombination reaction that replaces one immunoglobulin (Ig) heavy-chain constant region gene with another. This enables a single variable region gene to be used in conjunction with different downstream heavy-chain constant region genes, each having a unique biologic activity. AID, a putative RNA editing enzyme, is required for this action.