Polyclonal antibodies can be generated against almost any protein of interest by repeatedly injecting the purified protein into an animal (such as a rabbit) and collecting blood serum once the animal's immune system has produced antibodies against the protein. In this process, the antigen is not injected alone; it is co-injected with a so-called adjuvant to "trick" the immune system. Additionally, the adjuvant used in the first injection is often different from that used in later "booster" injections. Freund's complete adjuvant (C) contains a water-oil emulsion plus heat-killed Mycobacteria. In contrast, Freund's incomplete adjuvant (I) lacks the Mycobacteria component. Which adjuvant (C or I) do you think is used in the booster injections? Which immune response-primary (P) or secondary (S)-is triggered after the first purified protein injection? Activation of which antigen-specific immune cells-memory (M) or effector (E)-is chiefly responsible for the "boosting" effect of the later injections? Write down your answer as a three-letter string, e.g. ISM.