Influence of BCG administration time on the in-vivo migration of leukocytes.

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.