FIG. 2.

Antibody independence and CD4⁺ T-cell dependence of protection against NP challenge by 3P-CT. (A) Nasopharyngeal challenge of immunized μMT (Ig deficient) mice with strain 0603. μMT mice were immunized with CT, 3P-CT, or WCV-CT and subsequently challenged as described in the text. Density of colonization of each mouse is shown; lines represent median densities of colonization. Mice immunized with 3P-CT or WCV-CT had significantly lower densities of colonization than mice that received CT alone. (B) Effect on protection against NP challenge of CD4⁺ or CD8⁺ T-cell depletion of immunized wild-type mice. C57BL/6 mice immunized with 3P-CT received anti-CD4⁺ or anti-CD8⁺ T-cell antibodies at the time of challenge. Whereas mice that received anti-CD8⁺ antibodies were significantly protected against colonization, the administration of anti-CD4⁺ antibodies abolished protection by the 3P-CT. Density of colonization of each mouse is shown; lines represent median densities of colonization. (C) Measurement of IL-17A secretion by splenocytes. Splenocytes from immunized and control mice were stimulated with individual proteins for 3 days as described in the text; supernatants were collected and assayed for IL-17A concentration by ELISA.