IMMUNE PHENOTYPE OF CANINE HEMATOPOIETIC PROGENITOR CELLS

The immune phenotype of canine hematopoietic progenitor cells was stud ied by immunoseparation and culturing of separated cells. Two separati on methods were used, the magnetic cell sorting system (MACS) and the fluorescence activated cell sorter (FACS). For separation rat anti dog antibodies Dug 13 and Dog 14 directed against Thy-1, and Dog 26 as we ll as cross-reactive: mouse anti human antibodies IOT2a and 7.2 direct ed against MHC class II were used, Separated cell populations were cul tured in semisolid agar before and after long-term culture on a pre-es tablished irradiated stromal cell layer. After 28 days, adherent and n onadherent cells were harvested from lung-term culture. The MACS syste m allowed separation of cells into positive and negative fractions, Lo ng-term culture-initiating cells (LTC-IC) were found in both the Thy-1 (+) and the Thy-1(-) fraction, but the content of LTC-IC was higher in the Thy-1(+) fraction. The MACS system did not allow separation of pr ogenitor cells according to the expression of MHC class II antigen det ected by Dog 26 and the cross-reactive antibodies IOT2a and 7.2, In co ntrast to the MACS system the FACS allowed separation of negative, low -positive and high-positive cell populations, Low-positive fractions w ere well defined for Thy-1 and less well defined for MI-IC class II, C FU before and after long-term culture were exclusively observed in the low positive fraction (Thy-1(lo+)). Using MHC class II antibody Dog 2 6 LTC-IC were found mainly In the negative and low positive fraction, and CFU were observed mainly in the low and high positive fraction, In conclusion pluripotent canine hematopoietic precursor tells are low p ositive fur Thy-1 and for MRC class II. In this respect canine hematop oietic progenitor cells are comparable to those of mouse and man.