A specific micro-RNA (miR-6891-5p), which is encoded by an intronic sequence inside HLA-B, resulted to regulate the expression of the immunoglobulin heavy chain alpha 1 and 2 (IGHA1 and IGHA2) genes at the post-transcriptional level, thus potentially affect IgA levels and contribute to the development of SIgAD [48]. This evidence concerns the gene CD79A and selective IgA deficiency disease.