Immunology. Richard Coico

      1 E. Peptides ranging from 4 to 6 amino acids in length are low molecular weight molecules that are unable to generate antibody responses or T‐cell responses due to their small size. If these peptides were coupled or bound to a protein carrier, they could be immunogenic. T cells do not generate T‐cell responses to carbohydrates; therefore D is incorrect.

      2 B. The protection against smallpox provided by prior infection with cowpox is an example of antigenic cross‐reactivity. Immunization with cowpox leads to the production of antibodies capable of reacting with smallpox because the two viruses share several identical, or structurally similar, determinants.

      3 B. Conversion of a toxin to a toxoid is performed in order to reduce the pharmacological activity of the toxin so that sufficient toxoid can be injected to induce an immune response.

      4 E. Haptens are substances, usually of low molecular weight and univalent, that by themselves cannot induce immune responses (primary or secondary), but can do so if conjugated to high molecular weight carriers. The haptens can and do interact with the induced antibodies without it being necessary that they be conjugated to the carrier.

      5 D. An immunological adjuvant is a substance that, when mixed with an immunogen, enhances the immune response against that immunogen by mechanisms that depend upon the specific adjuvant used (e.g., enhanced antigen presentation, delayed release of antigen, etc.). It does not increase its size or chemical complexity. In addition, it does not enhance the immune response against a hapten, which requires its conjugation to an immunogenic carrier to induce a response against the hapten. The adjuvant has no relevance to possible toxicity of an immunogen.

      6 A. Polyclonal antibodies are a mixture of antibodies produced by multiple B‐cell clones with B‐cell receptors that react with specific antigenic epitopes expressed by the antigen. Antibodies can recognize single epitopes formed by primary sequence structures, or secondary, tertiary, and quaternary conformational structures. Denaturing a protein by disrupting disulfide bonds generally destroys conformational determinants. Therefore, it is likely that the polyclonal antibody reacts with nonconformational epitopes present on both native and denatured antigen, while the monoclonal antibody reacts with a conformational determinant only on the native antigen.