Epigenetic modifications cause heritable changes in gene expression which are not due to alterations in underlying DNA sequence. Inside the eukaryotic nucleus, there is condense packing of DNA around histone proteins to constitute chromatin structure. Epigenetic modifications are caused by factors that alter chromatin structure. Some epigenetic factors are enzymes that regulate DNA methylation and histone modifications, non-coding RNA, and prions. An offspring inherits parental epigenetic modifications but most of them are deleted and reset during early developmental stages. Some epigenetic modifications are retained and persist across multiple generations. If any epigenetic modification is the result of a stimulus or immune response in one generation, such that the modification continues to be inherited in subsequent generations which are not subjected to the stimulus; and the inheritance continues beyond the 3rd generation in the female germline and 2nd generation in male, then the phenomenon is called transgenerational epigenetic inheritance (TGEI). This entry is focused on a review which discusses some examples of TGEI that are reported in association with immune system development and disorders.
Various epigenetic mechanisms are caused by ncRNA which also regulate immune system development. Some examples are ncRNA-mediated histone and DNA modifications, and development of cells of the immune system.
Prions are misfolded proteins that are undergo TGEI and regulate stress response for survival. Prions are implicated in immune response under certain conditions. Certain epigenetic effects like histone modifications and gene expression are also mediated through prions.
Some disorders associated with the immune system how the presence of certain epigenetic modifications that underwent TGEI. Certain immune disorders, neurodegenerative and neurodevelopmental disorders show TGEI. Aging is another interesting field of research where TGEI is implicated. With the advent of advanced high-throughput technology coupled to next generation sequencing like ChIP-seq, ATAC-seq, RNA-seq, Hi-C, CUT&TAG, etc., the study of epigenetics if becoming more convenient, as described in the review.