Which phase of the primary immune response is characterized by no detectable antibodies?

The phase of the primary immune response characterized by no detectable antibodies is the lag phase. During this initial stage, which occurs after the introduction of a pathogen, the immune system is recognizing the antigen and beginning to mobilize immune cells. B cells are activated and start to proliferate and differentiate into plasma cells, but significant quantities of antibodies are not yet produced or released into circulation.

This phase can last several days to weeks, depending on various factors including the type of antigen and the overall health of the immune system. It is crucial for the establishment of a robust immune response, as it sets the groundwork for the subsequent production of antibodies during the log phase, when antibodies start to be detectable and rise sharply.

The log phase follows the lag phase and is where antibodies increase rapidly. The plateau phase occurs when antibody levels peak and stabilize, while the decline phase is characterized by a decrease in antibody levels after the immune response has resolved. Understanding these phases helps to elucidate the dynamics of the immune response and the timeline of antibody production.