Talk:Cytotoxic T cell

History of a cytotoxic T cell

I would like to know about the history of a cytotoxic T cell. I can't find anything on the web!== CD8+ T cells == If I remember correctly, CD8+ T cells equals cytotoxic T cells. The article is not clear on this point. / Habj 16:34, 21 December 2005 (UTC)

Yes, that is usually correct. I either have, or will make that association. The only problem is (and this is particularly true for CD4+ T cells) that there SOME exceptions to the rule, and this is where service as a general public encyclopedia versus a scientific review comes in. For example, cytotoxic CD4+ T cells do exist, but the incidence of these cells are very rare unless you enter certain disease states. I'm not particularly happy with how this immune page is written; whether that particular page is the best place to place TcR recombination (rather than a dedicated page, since it's a common step for all T cells), and information on how CD8+ T cells actually activate (versus what they do after they activate) is very lacking. The page is also not un-educated person friendly at all. There is no importance mentioned in how helper T cells are essential for their initial activation, or some of the safeguards the immune system has to prevent auto-immunity of cytotoxic T cells (e.g. co-stimulation is absolutely ESSENTIAL aspect in these cells). I could go on. This page was similar to the helper T cell page prior to me almost re-writing the entire page (there are a couple of original fragments, but you'd be lucky to find any more than one). I don't have the energy atm to re-write this page, I'd prefer to reference the helper page before I get stuck into the other immune cell pages.Volantares 12:35, 13 May 2006 (UTC)

Discussion of Pathogenesis

The mention of pathogenesis in various disease states is a good idea, although I feel that perhaps the pathogenesis section just needs a good introduction into the generalised role of cytotoxic T cells (i.e. they kill infected cells, but they have also been implicated in the pathogenesis of various illnesses). Is the discussion of the role of platelets in a Hepatitis B infection beginning to deviate from the purpose of this article? Wouldn't that specific result (especially since it isn't in a review) should remain in the pathogenesis section of Hepatitis B? Volantares 10:49, 6 July 2006 (UTC)

all the development can be described with all T lympocytes in the T cell article. Seems pointless to repeat it slightly differently in lots of places.

I think we're having this problem now between T cell and T helper cell as well. It may be necessary to coordinate editors for all three pages to come to relevant territorial consensus -- seeing as how it's mostly the same few people. <wink> Jbarin 08:13, 8 May 2007 (UTC)

AIDS Immunity

I think it is worth noting that this cell (particularly CD8 T Cells) are important in the small, very rare, population of people who have HIV but are immune (or at least very highly protected from) AIDS. —The preceding unsigned comment was added by 68.205.70.254 (talk) 05:15, 29 March 2007 (UTC).

Cytotoxic T cell development

This paragraph only talks about the Instructive Model Pathway for T cell development. There is another pathway, the Stochastic Pathway, which needs to be added and a statement that there is no general consensus over which one is correct, although most university teach the Instructive pathway. Scubafish 10:48, 29 May 2007 (UTC)

Then why don't you change it you friggin Know-it-all75.155.134.185 (talk) 02:43, 29 December 2008 (UTC)

Misleading Diagram

Resolved

 – Adrian J. Hunter^{(talk•contribs)} 11:49, 24 April 2011 (UTC)

Uh, unless I'm wrong, I find the first diagram a little misleading. It implies that it is the process of antigen presentation with the peptide that induces a T-cell to become CD4 or CD8 whereas it is infact the process of positive selection where if the T-cell interacts with MHCI then it is 8 and MHCII then it is 4, regardless of the antigen it encounters later on. —Preceding unsigned comment added by Cacofonie (talk • contribs) 12:38, 3 June 2008 (UTC)

I think you're correct. I left a comment on the T helper cell pages regarding this. M0rt (talk) 05:54, 31 May 2009 (UTC)

Actually, according to Janeway's Immunology, it's even more complex: double positive T cells randomly become single positive (SP) CD4+ or SP CD8+ cells, and then they will only survive if they have kept the marker that can function with the type of MHC their TCR recognizes; so, if a T cell's TCR recognizes CMH II and the T cell randomly chooses to keep CD8 and not CD4, it will die; thus, at this late stage during differentiation, T cells have a 1/2 chance of making the wrong random choice, and half of them die.

Also: "When these cells are infected with a virus (or another intracellular pathogen), the cells degrade foreign proteins via antigen processing." This is misleading: cells degrade all the time their proteins when they are recycled, not just when they are infected. Self peptides are presented on the surface of uninfected or infected cells, but T cells that could recognize these are destroyed during negative selection in the thymus. However, new, pathogen-derived peptides are presented on the surface of infected cells, and there is a proportion of immuno-competent mature T cells that can recognize these and hence detroy the infected cells. —Preceding unsigned comment added by 140.77.192.140 (talk) 16:28, 9 March 2010 (UTC)

Yes, I erased this diagram 2 hours ago because it is deeply wrong. Lymphocytes do not differentiate to CD4+ or CD8+ on the periphery, this is a solely thymic process. —Preceding unsigned comment added by 78.130.117.142 (talk) 17:43, 21 January 2011 (UTC)

Four people have now contested the accuracy of the diagram reproduced on the right, both in this thread and in this thread at Talk:T helper cell. The problem seems to be summarized in this edit summary by 78.130.117.142. I don't have the knowledge or sources to fix this myself, so for now I'm removing the diagram from the six articles that have it, and I'll notify the MCB and Medicine Wikiprojects. Adrian J. Hunter^{(talk•contribs)} 13:03, 22 January 2011 (UTC)

Actually, it is not well interpreted in the edit you are mentioning. There are two different processes that people here mixed together. First one is T-lypmhocyte differenciation which take place in the thymus and during which only cells recognizing foreign antigen are selected. Double positive CD4+/CD8+ thymocytes enter the thymus and leave as immature T-lymphocytes (either CD4+ or CD8+). Second process is T-lymphocyte maturation which occur at perifery or in lymph nodes. APC cell presents antigens on MHCII to immature CD4+ T-cell which then maturate to T_H1 or T_H2. Or an infected cell presents foreign antigens on MHCI to CD8+ immature T-cell which then becomes T_C.

So if this figure describes process of maturation, I suggest to either add text "CD4+ or CD8+" under the "Immature T cell", or to make a mirror figure - On one side APC with MHCII and leaving only Mature helper T cell, and on other side Infected cell with MHCI leaving the Mature cytotoxic T cell. --Mashin6 (talk) 00:35, 26 January 2011 (UTC)

I've restored the picture to all six articles following Mashin6's excellent fix. Note that due to the image being updated under the same name, the image that's showing in this thread is Mashin6's fixed version, not the disputed version that I removed. Adrian J. Hunter^{(talk•contribs)} 11:49, 24 April 2011 (UTC)

Killer T cells and the thymus

I want to know what is the relationship between Killer T cells and the thymus. — Preceding unsigned comment added by 96.252.155.69 (talk) 18:07, 6 May 2012 (UTC)

That's explained in http://en.wikipedia.org/wiki/Cytotoxic_T_cell#Development but I can understand how that might be unclear to the general reader. I was working on it, and I'll try to make it clearer. --Nbauman (talk) 14:34, 29 June 2012 (UTC)

Positive Selection

I thought Positive selection was when T-cells in the thymus are selected based on their TCR for their ability to recognize MHC class molecules. The article makes it seem like positive selection kills off those T-cells that bind too weakly, which does occur, but that is not positive selection I believe.

Activation Section Discrepancy

The second paragraph of the activation section currently says: "The threshold for activation of these cells is very high, and the process can occur via two pathways: thymus-independent (by infected APCs) or thymodependent (by CD4+ T cells). In the thymus-dependent pathway, because the APC is infected, it is highly activated and expresses a large number of co-receptors for coactivation. If APCs are not infected, CD4 cells need to be involved…"

In the second sentence, shouldn’t it say "thymus-independent" instead of "thymus-dependent"? It continues to say “because the APC is infected” and in the first sentence of the paragraph it says "thymus-independent (by infected APCs)". Also, in the third sentence it continues by saying “If APCs are not infected, CD4 cells need to be involved”, implying this is the alternate thymus-independent pathway even though the first sentence says “thymodependent (by CD4+ T cells)”. A bit confusing if you ask me. — Preceding unsigned comment added by CarlosArceDeza (talk • contribs) 16:36, 26 April 2022 (UTC)