DIFFERENTIAL-EFFECTS OF CHRONIC MONOCYTE DEPLETION ON MACROPHAGE POPULATIONS

  • 1 January 1983
    • journal article
    • research article
    • Vol. 49  (3) , 291-298
Abstract
The administration of the bone-seeking isotope, 89Sr, to mice results in severe monocytopenia without any apparent effect on the numbers of resident peritoneal macrophages (MO). An explanation for this dichotomy was sought by determining whether the residual blood monocytes were still an effective source of MO after 89Sr treatment. Stem cell enumeration showed that a 90% fall in bone marrow macrophage colony-forming cells after 89Sr was accompanied in little additional monocytopenia and had no affect on the numbers of resident peritoneal MO even when sampling was extended to 31 days, an interval beyond the accepted half-time for peritoneal MO. I.p. toneal injections of thioglycollate or Corynebacterium parvum elicited few or no monocyte-MO during respective intervals of 4 and 7 days. Elicitation with thioglycollate was attempted in thymidine 3H-labeled mice 26 days after 89Sr. Four days later only a 2-fold increase in labeled peritoneal MO was found in the 89Sr-treated mice compared with a 150-fold increase in the controls. Studies of the ectoenzymes 5''-nucleotidase, alkaline phosphodiesterase I and leucine aminopeptidase in such elicitation experiments suggested that the observed changes in activities reflected the direct stimulation of resident MO rather than monocyte immigration. Treatment with 89Sr apparently distinguishes 2 large populations of MO on the basis of their dependence on bone marrow. MO of inflammation reflect the monocytopenia and are severely and rapidly depleted by such treatment. The maintenance of resident type MO, on the other hand, appears to be independent of both the state of the bone marrow and the level of monocytes in the blood.