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Influence of BCG administration time on the in-vivo migration of leukocytes
J P Bureau1, G Labrecque, M Coupé
1Laboratoire de cytologie, Faculté de Médecine, Montpellier-Nîmes, France.
Abstract:
The temporal variation in the migration of polymorphonuclear leukocytes (PMN) induced by live BCG was studied in the mouse. Ten microliter of a 5 X 10(6) live BCG/ml suspension or sterile saline were placed on a cell trap immediately before its subcutaneous implantation at different clock times: 0100, 0500, 0900, 1300, 1700 and 2100 in animals synchronized with L(0700-1900): D(1900-0700). Eight hours later, the cell trap was removed, prepared for histological identification and counted. PMN counts in the cell trap were maximal 480 min after implantation. Non-specific migration was thought to occur and the peak value of leukocytes of 22.8 +/- 6.1 cells/10,000 micron 2 was obtained when the saline cell-trap was implanted at 0500. In the BCG-treated mice, a circadian rhythm was observed in the migration of leukocytes. The acrophase was at 1700. The results support the hypothesis that the circadian stage of antigen encounter influences the magnitude of the immune response.
Insights
The timing of antigen exposure significantly impacts immune responses. Circadian rhythms influence how polymorphonuclear leukocytes (PMN) migrate, with peak migration observed at specific times following BCG exposure.
Area of Science:
- Immunology
- Chronobiology
Background:
- Immune cell migration is crucial for host defense.
- Circadian rhythms are known to influence various physiological processes, including immune function.
Purpose of the Study:
- To investigate the temporal variation in polymorphonuclear leukocyte (PMN) migration in response to live Bacillus Calmette-Guérin (BCG).
- To determine if circadian rhythms influence the magnitude of the immune response to BCG antigen exposure.
Main Methods:
- Subcutaneous implantation of cell traps containing live BCG or saline at different clock times (0100, 0500, 0900, 1300, 1700, 2100) in synchronized mice.
- Histological identification and counting of PMN in cell traps 8 hours post-implantation.
Main Results:
- Non-specific leukocyte migration peaked 480 minutes after saline cell-trap implantation at 0500.
- BCG-treated mice exhibited a circadian rhythm in leukocyte migration, with an acrophase (peak) at 1700.
- The magnitude of PMN migration was dependent on the circadian timing of BCG administration.
Conclusions:
- Circadian stage influences the magnitude of the immune response to BCG.
- The timing of antigen encounter plays a critical role in modulating leukocyte migration patterns.