Many vaccines now in development will include highly purified, recombinant, or synthetic peptide antigens

Question

These vaccine antigens are expected to stimulate highly specific immune responses, but they are less immunogenic than vaccines containing intact killed or live microbes. Adjuvants are substances added to such vaccines to enhance their ability to elicit T cell immune responses. Which of the following statements about adjuvants is NOT correct?
A. Adjuvants induce local inflammation, thereby increasing the number of antigen-presenting cells (APCs) at the site of immunization.
B. Adjuvants stimulate the expression of costimulators on local APCs.
C. Adjuvants enhance local production of cytokines that promote T cell activation.
D. Adjuvants prolong the expression of peptide-MHC complexes on the surface of APCs.
E. Adjuvants bind to T cell antigen receptors and promote their proliferation.

Answer 1

ANS: E. Adjuvants are not necessarily T cell antigens. Some adjuvants may be T cell antigens, but their adjuvant activity is unrelated to their ability to be recognized, in peptide form, by T cells. Adjuvants are surrogates of the innate immune response to a microbe, required along with antigen component of a vaccine for naive T cell activation. Adjuvants stimulate local inflammation, influx of antigen-presenting cells (APCs), and activation of APCs to secrete cytokines and express costimulatory molecules, and they prolong peptide-MHC expression on the APC membrane.