Endocytic and NBT-reduction activities and TNF expression by macrophages and monocytes of the armadillo (Dasypus novemcinctus)

The armadillo could be considered as an experimental model for leprosy studies. Mycobacterium leprae main host cells are macrophages and Schwann cells. However، endocytosis and germicidal activities of armadillo macrophages and monocytes have not yet been evaluated. The aim of this research was to evaluate endocytosis and NBT-reduction activities of monocyte-derived macrophages (MDM) and monocytes from non-infected armadillos، as well as to determine tumor necrosis factor (TNF) levels during stimulation with phorbol myristate acetate (PMA). Mononuclear cells of peripheral blood were purified using the ficollhypaque technique. The monocytes obtained were transformed to MDM after being incubated for 8 days in an RPMI-1640 medium supplement with fetal calf serum at 37°C. Endocytosis and NBT-reduction were evaluated by yeast ingestion. TNF production by stimulation with PMA was evaluated through a bioassay with L-929 cells. The results revealed an endocytosis of 71. 77 ± 4. 11% and 60. 66 ± 6. 9% (P<0. 001) for armadillo MDM and monocytes respectively، whereas NBT-reduction was 16. 57 ± 4. 79% and 17. 66 ±4. 08%، respectively. With the addition of recombinant human IFNγ for 24 h، endocytosis and NBT reduction by MDM were 89. 92 ± 6. 17% (P<0. 001) and 36. 42 ± 4. 31% (P<0. 001)، respectively. Low levels of TNF are produced (10 U/ml) when MDM and armadillo monocytes are stimulated with 25 and 50 ng/ml of PMA، in comparison with human U-937 cells. In conclusion، MDM and armadillo monocytes show diminished activities in oxidative bactericidal mechanisms and in TNF production when stimulated with PMA.