engleski

Characterization of monoclonal antibodies that recognize canine CD34

Using a polyclonal antiserum against canine CD34, we previously found that CD34 is expressed on canine bone marrow progenitor cells in a manner analogous to that found in humans. In order to further characterize CD34^+ cells, and to facilitate preclinical canine stem cell transplant studies, monoclonal antibodies (MAbs) were raised to CD34. A panel of 10 MAbs was generated that reacted with recombinant CD34 and with CD34^+ cell lines, and failed to react with CD34^- cell lines. Binding properties of five purified MAbs were determined by BIAcore analysis and flow cytometric staining, and several MAbs showed high affinity for CD34. Two antibodies, 1H6 and 2E9, were further characterized, and in flow cytometry studies typically 1-3% of stained bone marrow cells were CD34^+. Purified CD34^+ bone marrow cells were 1.8-55 fold enriched for CFU-GM and for long-term culture initiating cells as compared to bone marrow mononuclear cells, whereas CD34^- cells were depleted of progenitors. Three autologous transplants were performed with CD34^+ cell fractions enriched by immunomagnetic separation. After marrow ablative total body irradiation (920 cGy), prompt hematopoietic recovery was seen with transplanted cell doses of less or equal to 1.1 x 10^7/kg that were 29% to 70% CD34^+. Engraftment kinetics were similar to those of dogs previously transplanted with approximately 10 to 100 fold more unmodified autologous marrow cells. This suggests that CD34 is not only a marker of canine bone marrow progenitors but also for cells with radioprotective or marrow repopulating function in vivo. MAbs to CD34 will be valuable for future studies of canine hematopoiesis, and preclinical studies concerning stem cell transplantation, gene therapy, and ex-vivo progenitor cell expansion.

CD34; monoclonal antibodies; autologous marrow transplants

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