Do T-cells express MHC molecules?

[Ganesh Ujwal]

T-cells recognize the MHC molecules and body's own peptides. When it doesn't, it alarms the immune system. But do T-cells express MHC molecules ? If so, how are they using it? If not, what happens when a virus infects T-cells? (Yes, I am confused about HIV infection mechanism too. They escape from immune response by altering their genes and disrupting the MHC-peptide bonding. I can see that this can work in macrophages. But what is the situation in T-cells ?)

[Vexen]

Hi,

 

In short, yes T cells and all other nucleated express MHC class 1 molecules.

 

There are two types of MHC molecules, MHC class 1 and 2. All nucleated cells express MHC 1 molecules when infected (including T cells). Cytotoxic T (CD8) cells only recognise MHC 1 molecules. When cells are infected with viruses, they express MHC 1 molecules.This allows cytotoxic T cells to destroy infected cells.

 

MHC class 2 molecules are only expressed by professional antigen presenting cells (APCs) such as macrophages. APC capture extracellular antigens and present them via MHC 2 molecules. The presented antigen is recognised by Helper T (CD4) cells(cytotoxic t cells cannot recognise MHC 2 molecules because they don't have CD4 coreceptors).

 

Human immunodeficiency virus (HIV) can only enter cells with CD4 coreceptors, thus HIV can only infect helper T cells and not cytotoxic T cells. For this reason, it is often said that HIV patients have a decreased CD4+ count. As a result, the effects of helper T cells are significantly reduced.

 

On a side note, if the CD4 coreceptors are mutated, HIV may not be able to infect helper T cells. Such occurrences have been reported.

 

Hope this post aids you.

I'm a student in South Africa (the country with the highest HIV prevalence) studying molecular biology.

Edited December 9, 2014 by Mikhail

[Vexen]

The attached picture shows the various receptors required by HIV to enter a cell.

 

See the following article for mechanisms of HIV:

 

HIV-1 Resistance to Maraviroc Conferred by a CD4 Binding Site Mutation in the Envelope Glycoprotein gp120

Annette N. Ratcliffa,b, Wuxian Shic and Eric J. Artsa,b (http://jvi.asm.org/content/87/2/923.full)

Edited December 10, 2014 by Vexen