Body Immunity Against Intracellular Viruses


Self-proteins from non-self proteins are viral that are distinguished by the major histocompatibility complex (MHC). This component is an important molecule involved in body immunity. The molecule signifies foreign molecules that may be present in the human body system.

The paper intends to analyze the importance of MHC molecules in T cell development, the role of TAP 1 and TAP 2 genes in the expression of MHC molecules on the surface of the cell, and the effects of mutations on the TAP-2 gene. Like in The case of Tanya, she has repeated infections that revealed IgG, white blood cell count, NK cells, and CD4+ which were all in the normal range except for CD8+.

Impact of MHC

Tanya has less than normal levels of MHC class I molecules on the surface. This will automatically result in a low CD8+ T cell response to viruses which will cause the repeated sinus infections, middle ear infections, and pneumonia. TAP-1 gene is important for antibodies because they identify human MHC molecules with leukocytes. This means that a defect in the TAP-1 gene will lead to an unstable HLA (human leukocyte antigen) complex.

Also, a mutation in the TAP-2 genes leads to a decrease in MHC Class I molecule and CD8+ cells. This is because TAP-2 works alongside TAP-1 and binds with ATP to transfer antigenic peptides to the endoplasmic reticulum. Unless they are bound to peptides, MHC class I cannot leave the endoplasmic reticulum. The MHC class I molecule contains cytotoxic T cell that defends against intracellular infection by having a cell surface molecule call CD8+. The CD8+ ensures that only antigens are presented bind to a certain site on MHC class I which are bound on the surface of the human cell.

The MHC class I molecule is involved with intracellular infections. Viral infections activate NK cells from the human innate system to promote the binding of viral peptides to the MHC class I molecule. This is done with the help of a proteasome. This is accomplished by adding a basic residue on the C-terminus. The viral protein must then be transported to the endoplasmic reticulum through the (transporter associated with antigen processing) TAP transporter. This is a heterodimer that consists of TAP-1 and TAP-2 chains. The transfer of the antigenic peptide is aided by ATP.

The discussion above clearly demonstrates that the major histocompatibility complex (MHC) plays a vital role in our human body immunity system especially regarding immune response. MHC class I molecules play the biggest part in T-cell activation and response and especially in the transport of the antigenic protein by the aid of TAP proteins (1 &2). In case of A defect in any of the TAP proteins (1 &2), will have huge effects on fighting intracellular viruses.