The adaptive (aka “acquired”) immune system: from friend to foe

The purpose of the immune system is simple—protect the human organism from foreign (antigenic) invasion and resultant disease. The innate immune response (“our best friend”) does a great job of accomplishing that defense under most circumstances. But sometimes, innate immunity confronts an adversary (a pathogen) that overwhelms it and produces a “dysregulated,” adaptive immune response. The first clinical effect is acute inflammation with an array of familiar signs and symptoms (pain, redness, swelling, sometimes fever). If not reversed within days to weeks, this negative pathological condition progresses from the acute state to its more devastating successor, chronic inflammation (“our worst enemy”), and the progenitor of all human disease. This chapter presents the clinical, histological, and pharmacological stages and basic immunotherapeutic efforts to arrest and reverse the “inflammatory cascade.” Unsuccessful efforts allow the adaptive immune system and chronic inflammation to begin an inexorable, pathological course toward autoimmune disease, cancers, and the ravages of infectious pandemics like COVID19.