Re: normal levels of HLA-DR on CD4

Alice L. Givan (Alice.L.Givan@Dartmouth.EDU)
01 Apr 97 20:52:48 EST

Just to throw in my two cents: DR is an activation antigen on T-cells and, as
such, is expressed in low and variable amounts on these cells. For this
reason, it represents a particular challenge to quantitation by flow
cytometry. After activation of T-cells in culture, I believe that there is
continuum from low expressing cells to high-ish expressing cells. The number
of cells that are said to "express the antigen" therefore depends greatly on:
1) the sensitivity of the cytometer
2) the F/P ratio of the conjugated antibody
3) whether the staining technique is direct or indirect
4) what fluorochrome is being used
5) where you set the "marker" to dichotomize the negative and positive
populations (eg at the 1% or 2% or 5% level on the negative control)
6) what you use as the negative control.

In addition, depending on whether there has been polyclonal activation or not,
it may be that there is a continuous population of dimly expressing cells and
that talking about the "% positive" is not as meaningful as it would be if
there were a clear intensity distinction between positive and negative cells.

On B-cells it is easy --- as they are all positive and all very bright.
T-cells are harder.

Alice L. Givan
Englert Cell Analysis Laboratory
Dartmouth Medical School
Lebanon, New Hampshire
NH 03756 USA
tel 603-650-7661
fax 603-650-6130
e-mail givan@dartmouth.edu

Home Page Table of Contents Sponsors E-Mail Archive Web Sites

CD-ROM Vol 3 was produced by Monica M. Shively and other staff at the Purdue University Cytometry Laboratories and distributed free of charge as an educational service to the cytometry community. If you have any comments please direct them to Dr. J. Paul Robinson, Professor & Director, PUCL, Purdue University, West Lafayette, IN 47907. Phone: (765)-494-0757; FAX(765) 494-0517; Web http://www.cyto.purdue.edu , EMAIL cdrom3@flowcyt.cyto.purdue.edu