A highly purified pneumococcal polysaccharide (Type II SSS) is a very efficient inducer of delayed hypersensitivity in random-bred guinea pigs. The cellular reactivity induced by this polysaccharide administered subcutaneously in complete Freund's adjuvant is of "tuberculin type"; it increases in intensity with time after the sensitizing injection, as judged by skin tests, the macrophage inhibition reaction and transfer of reactivity by peritoneal exudate cells.

By contrast, the cellular reactivity induced by this immunogen in the absence of mycobacterial adjuvant has the characteristics of "Jones-Mote" reactivity. It is best seen at about 1 wk after sensitization; the reactions are characteristically little indurated and show histologic differences from tuberculin type responses; and the reactive state begins to disappear by 2–3 wk, with the accession of Arthus reactivity. This type of delayed reactivity may be related to an early phase of antibody synthesis.

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