CD34 enrichment
CD34 enrichment (also: stem cell enrichment ) is a process for isolating blood stem cells from bone marrow or leukapheresis preparations in order to be able to transplant them selectively ( stem cell transplantation ). The blood stem cells are recognized by the CD34 (or also by the CD133) antigen and separated from the other bone marrow or blood cells.
Procedure
In Europe, the CliniMACS system from Miltenyi Biotec has established itself as the standard process. Antibodies against the CD34 antigen, which are coupled to magnetic particles, are mixed with the stem cells. These bind specifically to the CD34 antigen and the stem cells are separated from the other blood or bone marrow cells in a magnetic field. A very high level of purity of the CD34 + stem cells is achieved through several successive isolation and washing steps. In addition, Baxter's Isolex process is also carried out, which works in a technically similar manner.
meaning
Stem cell enrichment can be used in autologous stem cell transplantation to remove residual tumor cells from the transplant. In the case of allogeneic stem cell transplantation, it can prevent the occurrence of a GvH reaction and, through the indirect T-cell depletion, enables a transplantation from HLA-non-identical donors. A disadvantage of the purification via the CD34 antigen is the activation that takes place as a result and thus the beginning of differentiation of the cells.
history
Soon after the discovery of the CD34 antigen as a marker for hematopoietic stem cells, methods for their isolation were developed. One of the first methods was "panning" using a cell culture bottle coated with CD34 antibodies . The bone marrow cells were added to the flask and the cells incubated for 30 minutes. The stem cells bound to the coated walls. The unbound cells were carefully washed out, and the bound stem cells were then detached from the bottle by tapping.
The Cellpro system, in which the bone marrow cells were passed through a column with a gel matrix to which CD34 antibodies were bound, achieved worldwide distribution. The stem cells were retained in the column and could then be recovered by stirring.
The Cellpro process was replaced by the Isolex process developed in the USA (Baxter) and the CliniMACS process developed in Germany ( Miltenyi Biotec ), both of which are still in use.