[rosie5]

Does anyone know whether MHC class II is expressed on pancreatic beta cells in all individuals, or only those with diabetes type 1?
I know it is involved in the autoimmune attack in type 1 diabetes, but I can't find anything to tell me if it is usually expressed on beta cells anyway without causing autoimmunity, or if this is a mutation.

Have looked online but haven't been able to find what I'm looking for!

[cptbigt]

It's been a long time but....

The HLA cluster of genes encode homologous cell-surface proteins divided into class I (A, B and C) and class II (DP, DQ and DR), which are all highly polymorphic and are essential for self versus non-self immune recognition - thus they are wild-type components of β-cells. If I remember correctly it's not a mutation as such but more polymorphic predispositions - two haplotypes in the class II HLA region are found in 90% of patients with type I diabetes - DR3-DQ2 and DR4-DQ8 while, DR15-DQ6, a third haplotype, confers protection against T1D development and is found in only 1% of those with T1D. The prevailing hypothesis as to how these allelic combinations confer such susceptibility is that these alleles bind auto-antigenic epitopes less efficiently and this results in incomplete development of T-cell self tolerance either in the thymus or periphery, thus leading to the auto-immune destruction we see in type 1 diabetes.

Hope this points in you a helpful direction I'm sure someone who is more medically orientated can help a bit more!

[rosie5]

Thank you, that's very helpful!

just to confirm, does this mean that all people express a type of MHC class II molecule on their β-pancreatic cells, but in those without type 1 diabetes, the haplotypes in the class II HLA region allow efficient binding of the MHC class II to to the epitopes of self-antigens, resulting in development of T cell self-tolerance which means there is no type 1 diabetes?