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
This archive was generated by hypermail 2b29 : Wed Apr 03 2002 - 11:58:02 EST