Antibody concentrations....

Mario Roederer (Roederer@Darwin.Stanford.EDU)
Thu, 13 Jun 1996 14:16:07 -0800

In regards to a recent question about a source of antibodies, Dr Hill replied:

> For flow, we use anti MET antibodies From UBI, catalog
> 05-237 (clone DO-24), the one listed for IPs. It works
> at 1 - 1.5 ug /10E6 cells
> (need to use a secondary for the fluorescent label).

I just want to add my annual reminder that the concentration of antibody to use
in a staining mixture is essentially independent of the number of cells being
stained, but is completely dependent on the stain volume! 1 ug of antibody is
more than enough for (in generaly) well over 10^8 cells expressing a typical
antigen--thus, it doesn't matter if you have 10^5, 10^6, or 10^7 cells in your
tube! Indeed, many antibodies will stain equally well at 10^8 cells (in, for
instance, 100 ul volume).

On the other hand, a reagent titred to be used in a 50ul stain volume may not
stain very well in 500 ul.

Specifically: 1 ug of antibody (IgG) is about 3.6 x 10^12 molecules--which (in
divalent fashion) binds 7.2x10^12 molecules of antigen. A typical antigen may
be present in concentrations of 10^4 to 10^5 per cell, meaning that 1 ug of
antibody would be enough to stain 7.2 x 10^7 to 7.2 x 10^8 cells. And, if only
10% of the cells express an antigen, you can multiply this by another factor of
10!

mr


Home Page Table of Contents Sponsors Web Sites
CD ROM Vol 2 was produced by 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:(317) 494-0757; FAX (317) 494-0517; Web http://www.cyto.purdue.edu EMAIL robinson@flowcyt.cyto.purdue.edu