Intestinal intraepithelial lymphocytes
Intestinal intraepithelial lymphocytes (IELs) are mostly T cells, which are continuously associated with gut epithelium.
1. The epithelial integrity is disrupted and IEL and intestinal
epithelial cell (IEC) are liberated into the medium without altering the
basement membrane.
2. The original protocols developed for IEL
isolation require dissection to remove Peyer’s patches, and mincing of
the tissue physically to disrupt the epithelium.
3. This method is limited by variable contamination of the IEL preparation with lamina propria lymphocytes.
4. These
protocols for IEL isolation have required enzymatic digestion,
chelation with agents like ethylene diamine-tetraacetic (EDTA), panning,
or magnetic bead separation.
5. None of the modifications have proven entirely satisfactory. An alternative method for IEL isolation then is developed.
6. Intestine
is everted, ligated, distended and then incubated with dithioerythritol
(DTE) and subjected to repeated rigorous vortexing.
7. Contamination of this IEL preparation with lymphocytes from lamina propria and Peyer’s patches is minimal.
8. The
low cell yield, however, makes it uncertain that phenotypic and
functional characteristics of IELs prepared in this way are
representative of the entire, much larger, IEL compartment.
9. To
address these issues, a new technique for the rapid isolation of large
numbers of highly purified IELs has been developed.
10. The
technique is based in part on the susceptibility of intestinal
epithelial cells to hypoxic conditions that leave the basement membrane
relatively undisturbed.
11. The method is rapid and requires neither
enzymatic digestion, nor surgical removal of Peyer’s patches, nor
vigorous mechanical manipulation of the intestine.
12. The yield of rat IELs using this method is 5- to 10-fold greater than that reported by other methods.
13. Morphological
and phenotypic analyses demon- strated that the purified cell
population is comprised of IELs and is not contaminated with lamina
propria or Peyer’s patch lymphocytes.
14. In the original protocols developed for IEL enrich, one-step Ficoll density gradients is commonly used.
15. It is effective in separating lymphocytes from more dense cells but not from less dense cells, such as epithelial cells.
16. The use of a separating medium such as Percoll which is adjusted to various densities by dilution is recommended.
17. Usually, a first centrifugation in 30% Percoll is performed and then a discontinuous gradient is applied.
18. The usual layers for the second Percoll are 20%-44%-67% for human cells and 30%-40/45%-75% for mouse or rat cells.
19. This procedure implies a low cell recovery but purity is usually good (90% IELs) though lower for human samples (60%-70%).
20. This
final step involves staining IELs if their positive selection is
preferred (with an antibody such as anti-CD45) or IEC if their depletion
is favored (with anti-epithelial markers).
21. In the case of
magnetic methods, which offer better viability, anti-Ig-coated
paramagnetic beads are generally used to label the cells to be retained
in the magnet.
22. Depletion of IEC provides with untouched IELs, and markers such as cytokeratin or BerEP47 have been used for the purpose.
Reference
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