HLA system in solid organ transplantation part 14

The genes encoding class I HLA molecules extend by approximately 2 million nucleotide bp, consisting of three main isotyped HLA-A, -B and -C, which participate in the presentation of endogenous antigens, but other genes encoding distinc non classical or class I-like molecules (HLA-E, -F and -G) with roles in natural killer cell function or foeto-matenal immunity, as well as some pseudogenes (HLA-H,-J, -K and -L) and other genes fragments (HLA-N, -P, -S, -T, -U, -V, -W, -X, -Y and -Z), can also be found  within this region. The most likely role of these pseudogenes and gene fragments is to serve as genetic reserve to provide genetic material for gene conversion to increase further the diversity of HLA alleles. In contrast, the class II HLA molecules extend for around 1 million nucleotide bp and their main representatives are the HLA-DR, -DP and -DQ molecules