| Description |
Purified protein derivative is the skin sensitin most commonly used to detect tuberculin sensitivity. Although PPD is a more specific sensitin than "old tuberculin," it still lacks specificity and will induce significant reactions in individuals sensitized to mycobacteria other than M. tuberculosis. The object of this research was to remove constituents from PPD which contribute to its nonspecific activity. When PPD was subjected to column chromatography using Sephadex G-300 three fractions resulted. Fraction I contained materials in the first peak which came off with the void volume. The molecular weight of these materials should be greater than 800,000 daltons, Fraction III contained materials in the second peak. The approximate molecular weight was 36,999. Fraction II was comprised of the substances eluted between the two peaks. The molecular weight or constituents in this fraction was between, 111,000 - 3000,000. Immunoelectrophoresis and immunodiffusion demonstrated that three fractions contained two precipitinogens which were electrophoretically immobile. Fraction II contained two components which migrated to the cathode, and fraction III contained one component which migrated to the anode. By combining the data from immunoelectrophoresis, immunodiffusion and the skin test, it was concluded that each fraction contained at least one unique component. Guinea pigs sensitized to either Guinea pigs sensitized to either M. tuberculosis, M. kansasii, M. scrofulaceum, M. intracellulare, or M. gordonae were skin tested the three fractions. All fractions elicited strong homologous reactions. Fraction I was the most highly cross reactive in guinea pigs sensitized to the mycobacteria other than fraction I or whole PPD. The cross reactions to both fractions II and III averaged well below 5 mm in diameter. The results suggests that fraction I could be discarded and fractions II and III could be used separately or together (pooled) to provide a sensitin more specific than PPD. The migration inhibition test has been recently suggested as an in vitro test for delayed hypersensitivity (FH). It is important to know if the MI test can be used to quantitate DH and if the reaction observed in the MI test correlate with the reactions seen in the tuberculin skin test. Guinea pigs sensitized to various species of mycobacteria were skin test with a multiplicity of sensitins. Peritoneal exudate cells from these sensitized animals were use in the MI test to study the response to the same sensitins. Each MI reaction was compared to the appropriate skin reaction to determine if a quantitative correlation existed between the two reactions. The MI reactions did not have a high degree of correlation with the skin test reactions. Weak skin reactions were found to frequently correspond to strong MI reactions. Also animals which reacted poorly (weak reactors) to all sensitins were sometimes strong reactors in the MI test. The MI test appeared to be more sensitive than the tuberculin skin test. However, the MI test was not capable of distinguishing homologous reactions from cross reactions. The accumulated data indicated that the MI test has greater sensitivity but decreased specificity when compared to the tuberculin skin test. |
