An antibody made against the antigen tetanus toxoid (tt) reacts with it even when the tt is denatured by disrupting all disulfide bonds. Another antibody against tt fails to react when the tt is similarly denatured. The most likely explanation can be stated as follows:

Answer;

-The first antibody is specific for the primary amino acid sequence of TT, whereas the second is specific for conformational determinants.

Explanation;

-Antigen-antibody reaction, is a specific chemical interaction between antibodies produced by B cells of the white blood cells and antigens during immune reaction. The specificity of the binding is due to specific chemical constitution of each antibody.

-The amino acid sequence in the tips of the "Y" varies greatly among different antibodies. This variable region, composed of 110-130 amino acids, give the antibody its specificity for binding antigen. The variable region includes the ends of the light and heavy chains.