Early colonisation of a local inflammatory lesion and its relationship to changes in systemic leucocyte availability: a study of turpentine-induced lesions in the rat.

The changes in both peripheral blood leucocyte counts and lesion inflammatory cells have been measured at intervals up to 24 hr following the subcutaneous injection of turpentine in rats. The lesion PMNL changes were characterised by a sharp rise between 0 and 6 hr and a less-rapid fall between 6 and 24 hr. The half-life of lesion PMNL's, as determined by tritiated thymidine labelling between 12 and 24 hr after turpentine injections, was 13 hr and there was a significant correlation between blood and lesion PMNL counts throughout the experimental period. A dependence of the lesion PMNL population on the availability of these cells is thus suggested. Mononuclear cells, which were predominantly monocyte-derived, showed a sharp rise between 6 and 12 hr, plateauing thereafter. These changes were not associated with significant alterations in blood monocyte counts. Although significant changes in blood lymphocyte counts were observed, these were not reflected in the local inflammatory lesion.