{"id":1377,"date":"2009-04-19T23:13:03","date_gmt":"2009-04-19T23:13:03","guid":{"rendered":"http:\/\/localhost.localdomain\/wpmu\/htb\/?p=1377"},"modified":"2013-08-16T14:37:17","modified_gmt":"2013-08-16T14:37:17","slug":"cd4-t-cell-responses-to-commensal-bacteria-in-the-gut","status":"publish","type":"post","link":"https:\/\/i-base.info\/htb\/1377","title":{"rendered":"CD4 T-cell responses to commensal bacteria in the gut"},"content":{"rendered":"

Richard Jefferys, TAG<\/strong><\/p>\n

There has been a lot of attention given recently to the role of gut CD4 T cell depletion in HIV pathogenesis. Surprisingly, very little is known about which antigens are targeted by gut CD4 T cells; at least one study has reported evidence of memory CD4 T cell responses to candida albicans (the fungus that causes thrush) but an absence of the typical memory responses against opportunistic pathogens (also called \u0093recall responses\u0094) found in the blood.<\/strong> [1]<\/p>\n

More recently, gut HIV-specific CD4 T cell responses have been detected some elite controllers [2] and in HIV-infected individuals showing robust CD4 T cell recovery in the gut on antiretroviral therapy (this latter data was presented at CROI by Satya Dandekar. [3] Studies in mice have suggested that there are likely be CD4 T cell responses to commensal bacteria in the gut, but there is little research addressing this question in humans. In a new paper in press at Clinical Immunology, Rawleigh Howe and colleagues from Cara Wilson\u0092s group at the University of Colorado describe their initial efforts to fill this knowledge gap. [4]<\/p>\n

Using flow cytometric techniques, the researchers were able to detect the presence of CD4 T cells making interferon gamma in response to stimulation with several gut commensal bacteria species (Enterobacter, E. coli, Enterococcus species) as well as to the pathogen, Salmonella typhimurium. CD4 T cells making IL-17 \u0096 Th17 cells \u0096 were also detected but at a much lower frequency. Bacteria-specific CD4 T cell responses could also be detected in the blood but at significantly lower levels; the difference in magnitude between gut and blood ranged from 8.5 to 19.5 fold. When responses to all four bacterial antigens were summed, the median frequency of interferon gamma-producing CD4 T cells was 0.24% in the gut compared to 0.02% in blood.<\/p>\n

The researchers suggest that the CD4 T cell responses revealed in this study play a role in containing bacteria in the gut under normal conditions. Such a role would be consistent with recent studies indicating that T cell depletion can lead to systemic dissemination of gut bacteria (microbial translocation). Another implication of the data is that people with HIV infection may have altered CD4 T cell reactivity to commensal bacteria, and Cara Wilson\u0092s group is addressing this possibility in ongoing studies.<\/p>\n

Source:
\nTAG Basic Science Weblog. (23 Feb 2009)
\nhttp:\/\/tagba sicscienceproject.typepad.com\/tags_basic_science_vaccin\/2009\/02\/cd4-t-cell-responses-to-commensal-bacteria-in-the-gut.html<\/a><\/p>\n

References:<\/p>\n

    \n
  1. http:\/\/www.ncbi.nlm.nih.gov\/pubmed\/7492350<\/a><\/li>\n
  2. http:\/\/tagbasicscienceproject.typepad.com\/tags_basic_science_ vaccin\/2009\/01\/muco.html<\/a><\/li>\n
  3. http:\/\/app2.capitalreach.com\/esp1204\/servlet\/tc?c=10164&cn=retro&e=10652&m=1&s=20415&&espmt=2&mp3file=10652&m4bfile =10652<\/a><\/li>\n
  4. Howe R et al. Evidence for dendritic cell-dependent CD4+ T helper-1 type responses to commensal bacteria in normal human intestinal lamina propria. Clinical Immunology. doi:10.1016\/j.clim.2008.12.003. Article in press.<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"

    Richard Jefferys, TAG There has been a lot of attention given recently to the role of gut CD4 T cell depletion in HIV pathogenesis. Surprisingly, very little is known about which antigens are targeted by gut CD4 T cells; at …<\/p>\n","protected":false},"author":4,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[15],"tags":[],"class_list":["post-1377","post","type-post","status-publish","format-standard","hentry","category-basic-science-and-immunology"],"_links":{"self":[{"href":"https:\/\/i-base.info\/htb\/wp-json\/wp\/v2\/posts\/1377","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/i-base.info\/htb\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/i-base.info\/htb\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/i-base.info\/htb\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/i-base.info\/htb\/wp-json\/wp\/v2\/comments?post=1377"}],"version-history":[{"count":0,"href":"https:\/\/i-base.info\/htb\/wp-json\/wp\/v2\/posts\/1377\/revisions"}],"wp:attachment":[{"href":"https:\/\/i-base.info\/htb\/wp-json\/wp\/v2\/media?parent=1377"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/i-base.info\/htb\/wp-json\/wp\/v2\/categories?post=1377"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/i-base.info\/htb\/wp-json\/wp\/v2\/tags?post=1377"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}