IMMUNE CELL DEFECTS AFFECT BONE REMODELING IN OSTEOPETROTIC OP OP MICE/

The aim of the present work was to further characterize immunological defects in osteopetrosis. The op/op mutant mouse is of particular inte rest since a marrow cavity develops spontaneously in older animals. Th e interleukin production (IL-1, IL-2, IL-3, IL-4, IL-6), the presence of macrophage differentiation antigens and the evolution of the bone l esions were studied in osteopetrotic and normal mice. Low levels of IL -l, IL-3 and IL-4 were observed at the age of 6 weeks in the op/op mic e. However, at 22 weeks of age, the level of IL-I and IL-4 returned to normal value in these op/op mice whereas the level of IL-3 remained p artially decreased at the same age. Furthermore, macrophage expression of MAC-2 antigen, reduced at 12 weeks of age was found to be normal 1 0 weeks later. These immunological defects and their recovery seems to be concomitant with the healing of the bone lesions.