The virulence-enhancing factor of mucins. 4. The role of particulate insoluble matter and a viscous medium in virulence enhancement, with a revised assay of the third factor involved

In Part 3 (Smith, 1951) of this series a virulence- enhancing fraction of hog gastric mucin was sep- arated from the insoluble particulate residue. This residue had an adjuvant action on the enhancement ofthe virulence by the activefactor comparable with that already demonstrated (Smith, 1950b) for the viscosity of the original mucin. However, using a biological assay involving a medium of constant viscosity for injection, no residue was obtained com- pletelyfree from virulence-enhancing activity, even after autoclaving and washing with hot water. The suggestion was made, therefore, that a viscous medium, together with the particulate residue, could impede the host defence mechanisms by themselves, quite apart from their probable action in delaying the absorption by the host of the active factor. This suggestion is supported by the work of Olitzki & Koch (1945), who reported the adjuvant action of kaolin, fuller's earth, Norit A and talcum on the small virulence-enhancing activity of 0-3 % agar for