The Specific Precipitin Reaction

Evidence has been put forward that the biological activity of these 

A preliminary chemical investigation of the polysaccharides of M. tuberculosis has recently been undertaken by W. N. Haworth and the authors. It was found that two stable and probably degraded polysaccharide fractions could be isolated from the defatted cells by the action of sodium hydroxide. Both products were serologically active at a dilution of 1 2,000,000 the first fraction ([a] D + 85° in water) was derived mainly from the somatic portion of the cell, while the second + 27° in water) was found in the ether-soluble lipid constituents. Both fractions were intimately associated with deoxyribonucleic acid, which was identified by nitrogen and phosphorus analyses, by the Dische test and by spectrophotometric measurements. 

This nucleic acid could be separated only with difficulty from the polysaccharides. Both polysaccharides were smoothly converted into the corresponding neutral methyl ethers, which contained 0.3% nitrogen. 

The methylated somatic polysaccharide has been hydrolyzed, and from the mixture of partially methylated sugars so formed, methyl 3,4,6-trimethyl-D-mannopyranoside (25%), methyl 3,4-dimethyl-D-man-nopyranoside (20%), methyl 2,3,4-trimethyl-L-rhamnopyranoside (25%) and methyl 3,5-dimethyl-n-arabofuranoside (25%) have been charac- 

The available evidence indicates that in the somatic polysaccharide, L-rhamnose residues are present in the pyranose form and are combined glycosidically as terminal groups. Some of the D-mannose residues are linked through the 1 and 2 positions while other D-mannose residues are linked in the 1, 2 and 6 positions. D-Arabinose is present in the furanose form linked in the 1 and 2 positions. 

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Three characteristic biological reactions can be ascribed to special polysaccharide components of M. tuberculosis. These are the typical skin reaction, usually termed the tuberculin reaction, certain cellular reactions, and the specific precipitin reaction. 

When tested against antibodies eluted from the column by iV-ace-tylgalactosamine, the A(-acetylgalactosamine inhibited the specific precipitin reaction with A substance, whereas there was no appreciable inhibition by A -acetylgalactosamine of antibodies eluted with the pentasaccharide. The results were interpreted on the basis that the sizes of the combining sites of anti-A substance vary markedly in the human antibody population. 

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