Indirect blastogenesis of peripheral blood leukocytes in experimental gingivitis

The blastogenic response of peripheral blood leukocytes to lipopolysaccharide (LPS) was followed over a short course of experimental gingivitis, developed in human volunteers who strictly avoided oral hygeine procedures for periods up to 9 days. Eleven young males initially received thorough dental prophylaxes and supervised oral hygeine until they acquired optimal gingival health. At this point, leukocytes (5 X 10(5)) incubated with 1.5 to 25 mug of LPS in serum-free media showed no response as measured by tritiated thymidine uptake. Coincubation of cells with LPS and phytohemagglutinin (PHA), however, caused synergistic enhancement of blastogenesis in every LPS-PHA dose combination tried. With progressive accumulation of dental plaque and the concomitant development of gingival inflammation, this synergistic response was lost and replaced, proportionately, by a direct response to LPS. The leukocyte response to PHA was marginally enhanced with gingivitis.