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The concentration of alpha 2-macroglobulin (alpha 2-M) in human gingival sulci has been investigated in two studies: first, in gingival washings during a 21-day period of experimental gingivitis in eight human volunteers and, second, in crevicular fluid collected with filter paper strips before and after initial periodontal therapy in 11 patients. The concentration of total alpha 2-M was found to increase in the washings of the volunteers throughout the period of experimental gingivitis. In the group of patients receiving periodontal therapy, the absolute amount of alpha 2-M in the fluid showed a significant decrease after therapy. The gingival index of inflammation and the crevicular fluid flow also decreased significantly. The specific content of the inhibitor (micrograms of alpha 2-M per mg of fluid per min), however, was found to increase in the fluid with decreasing inflammation. As detected by crossed immunoelectrophoresis, the fluid collected in these patients before therapy, in the presence of severe inflammation, invariably showed peaks of both free and complexed alpha 2-M. In contrast, the fluid collected from the same sites after healing of the inflammation contained no detectable free alpha 2-M.

Samples of hydroxyapatite (HA) beads smaller than 1 mg were coated with 10 microliter of either saliva, serum, or human crevicular fluid before being added to a suspension of Streptococcus sanguis or Bacteroides gingivalis. In some assays, preparations of a granular fraction, elastase, or cathepsin G from human leukocytes were used to coat HA or to treat saliva-coated HA (SHA) before mixing with bacteria. The number of cells adhering to the beads was then counted under a scanning electron microscope by a standardized procedure. More cells were found to adhere to SHA in this assay than in the conventional large-scale assay. Human crevicular fluid, even when diluted up to three times, completely inhibited the adherence of S. sanguis to HA. A 100% inhibition of S. sanguis adherence was also observed when HA was coated with the granular fraction of leukocytes, and a 65% inhibition observed when SHA was treated with the enzyme preparation. When used to coat HA, elastase and cathepsin G reduced the adherence of S. sanguis by 30 and 50%, respectively. The binding of S. sanguis to elastase- or cathepsin G-treated SHA was also reduced. B. gingivalis 33277 was found to adhere in high numbers to SHA. Coating HA with crevicular fluid or with the lysosomal enzyme preparation had a limited negative effect. We postulate that crevicular fluid prevents the adherence of S. sanguis by virtue of either its enzyme content or its albumin content or both.