One should not equate CD4/CD8 double-positive peripheral blood cells with CD4/CD8 double-positive thymocytes. In fact, the term "double positive", while simple, can be misleading as it does not contain information about staining intensity, or about the subunit composition of the stained antigen. There are several papers that characterize the phenotype(s) and function(s) of CD4+/CD8dim cells. For example: Suni, M. A., S. A. Ghanekar, D. W. Houck, H. T. Maecker, S. B. Wormsley, L. J. Picker, R. B. Moss, and V. C. Maino. 2001. CD4(+)CD8(dim) T lymphocytes exhibit enhanced cytokine expression, proliferation and cytotoxic activity in response to HCMV and HIV-1 antigens. Eur J Immunol. 31:2512-20. Gib Otten Chiron Corp. 4560 Horton St., M/S 4.3 Emeryville, CA 94608 Telephone: 510-923-2965 mailto:Gillis_Otten@chiron.com -----Original Message----- From: Maciej Simm [mailto:simmmmer@yahoo.com] Sent: Friday, November 09, 2001 6:19 PM To: cyto-inbox Subject: RE: RE: cd4 cd8 coexpression Howard, In my opition - we look for CD4+ events in HIV patients to help us get an idea of the state of the immune system of an HIV/AIDS patient(as one of many assays). The virus attacks CD4+ cells, with preference for TH lymphocytes (as opposed to DC's and monos etc etc), and as Mario Roederer et al. showed using 11 color flow (if I remember right), memory cells are more volnurable than naive cells. According to my immunology textbook, double positive T cells are undifferentiated T cells that have yet to undergo T cell receptor rearrangement, so they're FAR from functional T lymphocytes that can help in fighting the HI-virus. Therefore, in my opinion, double positive T cells should not be included in HIV patiens' T cell assessment. In fact I would go as far as proposing that we look for remaining MEMORY CD4+ T cells in HIV patients. maciej --- Howard.Gale@med.va.gov wrote: > > As I said in a previous message, the CD4+/CD8+ T-cells(CD3+)in our > HIV+ > patients come in all varieties of brightness. The acquistion rate > is in the > 100-400 events/second range and I see no evidence of this being a > doublet > problem in the SSC vs CD45, CD3 vs CD4, or CD3 vs CD8 cytograms. > These > populations present consistently in patients over time and > occasionally are > a significant part of the CD+/CD3+ count. Is there any evidence > that these > dual positive cells (should not be counted as T-helper cells)and > does the > amount of relative fluorescence of CD4 and CD8 matter? > -----Original Message----- > From: Jacek Polski [mailto:jpolski@usouthal.edu] > Sent: Thursday, November 08, 2001 10:33 AM > To: cyto-inbox > Subject: Re: RE: cd4 cd8 coexpression > > > > This may well be the answer to this intellectually stimulating > issue, but > the > CD4+CD8+ events in my experience (usually below 1%) have the same > intensity > of CD8 as > suppressor cells and slightly lower CD4 expression than helper > cells. In my > opinion, > this observation supports the previously posted notion that CD4 can > be > expressed on > activated CD8+ cells. > Regards, > Jacek Polski, MD > Univ. South Alabama > > > >>> <Alice.L.Givan@dartmouth.edu> 11/06 6:45 PM >>> > > Hello Flowers, > I just wanted to re-inforce Ken Ault's comments about artifactual > co-expression of CD4 > and CD8 due to coincidence of two cells in the laser beam. Two > cells can > coincide in > the beam either because they are physically aggregated into a clump > or > because they > just happen (by statistical probablility) to be suspended in the > same > volume of sample > buffer as it moves past the laser. > > A coincidence artifact should be suspected if: > 1) as Ken said, the frequency of these CD4/CD8 doubles decreases > when the > flow rate > is decreased (although this may not happen if the cells are in > actual > clumps). > 2) the intensity of each color on the double expressors is the > same as the > intensity of > each color on the relevant single expressors. In other words, if > the double > expressors > form the fourth corner of a perfect rectangle on a dot plot (with > the negs, > the PE+ > singles, and the FITC+ singles forming the other three corners), > then you > should > be suspicious. > > Alice > > > Alice L. Givan > Englert Cell Analysis Laboratory > of the Norris Cotton Cancer Center > Dartmouth Medical School > Lebanon, New Hampshire NH 03756 > tel 603-650-7661 > fax 603-650-6130 > givan@dartmouth.edu > __________________________________________________ Do You Yahoo!? Find a job, post your resume. http://careers.yahoo.com
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