<unk>  II The genetic basis for<unk> II is not due to defects in the MHC II genes themselves. The genetic basis is the result of mutations in genes that code for proteins (transcription factors) that normally regulate the expression (gene transcription) of the MHC II genes. That is, one of the several proteins that are required to switch on MHC II genes in various cells types (primarily those in the immune system) is absent. The genes responsible were cloned by the laboratories of Bernard Mach in Switzerland and Jeremy Boss at Emory University in Atlanta, Georgia. Mutation in any one of four genes can lead to<unk>  II. The genes' names are: * class II trans-activator (CIITA) * regulatory factor of the Xbox 5 (RFX5) * RFX-associated protein (RFXAP) * RFX ankyrin repeats (RFXANK; also known as RFXB)<unk>  I<unk>  I, also called "HLA class I deficiency", which is much more rare, is associated with TAP2, TAP1, or TAPBP deficiencies. The TAP proteins are involved in pumping degraded cytosolic peptides across the endoplasmic reticulum membrane so they can bind HLA class I. Once the peptide:HLA class I complex forms, it is transported to the membrane of the cell. However, a defect in the TAP proteins prevents pumping of peptides into the endoplasmic reticulum so no peptide:HLA class I complexes form, and therefore, no HLA class I is expressed on the membrane. Just like<unk>  II, the defect isn't in the MHC protein, but rather another accessory protein.
Bare lymphocyte syndrome
Kasabach–Merritt syndrome
Adult-onset immunodeficiency syndrome
Diffuse infiltrative lymphocytosis syndrome
Mast cell activation syndrome
Pitt–Hopkins syndrome
EAST syndrome
OSLAM syndrome