INVESTIGATION

Transporter associated with antigen processing (TAP)

TAP is a membrane-spanning heterodimer that consists of two proteins, which are TAP1 and TAP2. The TAP1 & TAP2 each have their domains that appear in the rough endoplasmic reticulum and an ATP-binding domain appearing in the cytosol. TAP is found in the cell membranes of bacteria. They mediate ATP-dependent transport of sugars, amino acids, and peptides. These protein transport peptides that interact with MHC class I. However, there is a thing as TAP deficiency, and this is when there's a downregulation of peptide uptake and no new MHC class I molecules are produced. An example of this condition is the bare lymphocyte syndrome (BLS)--a defect in TAP1 and TAP2 gene. The lymphocytes in patients suffering from this disorder refuse to express MHC molecules, and if they do, it is below average levels. There are type1 BLS & type2 BLS. In type 1, MHC class I molecules are not being expressed while in type 2, expression of MHC class II is not being expressed. Besides peptides unable to bind to class I molecules, other abnormalities are increased NK cells and decreased levels of CD8 T-cells. I believe the reduced levels of CD8 is due to the lack of CD4 cells since they activate both B cells and cytotoxic CD8 cells. And because of this, their ability to fight off infections is significantly affected, individuals tend to get viral and bacterial infections often. Although, I think the NK cells are elevated because it just makes sense. If your other cells needed to fight off infections aren't working, the cells you have that works would be twice as active. So, If your CD4 cells required to destroy a pathogen is absent, then the ones you do have would have to work twice as much; and maybe that might fight off some viral infections if possible.
Other [visible] symptoms include chronic skin lesion, sinusitis, possibly constipation, and anemia.
Treatments: bone marrow transplant, and possibly gene therapy.

Google images

References

•  Gadola, S. D., H. T. Moins-Teisserenc, J. Trowsdale, W. L. Gross, and V. Cerundolo. "TAP Deficiency Syndrome." Clinical and Experimental Immunology. Blackwell Science Inc, n.d. Web. 10 Nov. 2016. <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1905688/>.
• https://rarediseases.info.nih.gov/diseases/8427/bare-lymphocyte-syndrome

#happybloggin' :)