Ganesh Ujwal Posted December 8, 2014 Share Posted December 8, 2014 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 ?) Link to comment Share on other sites More sharing options...
Vexen Posted December 9, 2014 Share Posted December 9, 2014 (edited) 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 Link to comment Share on other sites More sharing options...
Vexen Posted December 10, 2014 Share Posted December 10, 2014 (edited) 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 Link to comment Share on other sites More sharing options...
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