The Correlation of Lactobacillus Count and Gamma Globulin Level of Human Saliva

Abstract

The observation that strains of Lactobacillus failed to grow in vitro in the presence of human fraction II globulin' led us to consider the possibility that Lactobacillus counts per cubic centimeter of saliva might be a function of gamma globulin levels of saliva. Recently, Green demonstrated that pooled saliva from caries-susceptible individuals contained less gamma globulin-active saliva samples than saliva from caries immune individuals.2 The objective of this investigation was to determine whether the gamma globulin level of saliva was in some way correlated with the Lactobacillus count obtained from such saliva. MATERIALS AND METHODSFive cubic centimeters of paraffin-stimulated saliva were collected from each of thirty-eight students 2 hours after breakfast. One cubic centimeter of saliva was used to inoculate Rogosa agar for culturing strains of Lactobacillus. Two cubic centimeters of saliva were used for total protein, alpha, beta, and gamma globulin determination, using the sodium sulfate method for precipitation, and were measured spectrophotometrically.Two cubic centimeters were used for direct qualitation of gamma globulin. In this instance, rabbit antihuman gamma globulin serum bound to latex* was used for macroscopic determination of precipitation of saliva gamma globulin.The method for Lactobacillus culture is well known and will not be described. The macroscopic precipitation test was carried out by centrifuging 1 cm3 each of boiled and raw saliva. One drop of the supernatant was diluted in saline-glycine buffer: 1/1, 1/4, 1/8, on an appropriate slide. One drop of the antihuman gamma globulin rabbit serum was added to each of the dilutions and read after 2 minutes. The clumping of the globulin-bound latex made macroscopic determination of antibody reaction possible. In view of false-positive tests secured with boiled saliva, the results will not be reported. However, in all cases of 1/1 and 1/4 dilution there was a positive test for gamma globulin. Roughly approximated, this is something below 50 mg. per cent of gamma globulin.The sodium sulfate determination of gamma globulin was carried out as follows: To a 0.5-ml. sample of the supernate of centrifuged saliva was added 9.5 ml. of 27.2