The HLA class III region genes are important elements in

*HLA class III region contains genes for early complement components C2 and C4 of classical pathway. *Deficiency of these early components of the classical pathway viz C1, C2 and C4 is associated with autoimmune diseases like SLE and other collagen vascular diseases. • These genes are thus, important in regulating susceptibility to autoimmune disease • Class III genes do not participate in MHC restriction or graft rejection components.