The authors describe the actions that take place in T cells because of their amazing capacity to proliferate and adopt functional roles aimed at clearing a host of an infectious agent. There is a drastic decline in the T cell population once the primary response is over and the infection is terminated. What remains afterward is a population of T cells with a "memory" for the pathogen they had just taken part in controlling. These remaining T cells, after the collapse of the primary response, are altered in their functional abilities. The authors further describe in this review that it does not incorporate all of the possible permutations that can and do exist in T cell responses generated in the real world, that is, the response that happens when everything is working exactly as it should, culminating in effective, long-lived memory against an infectious pathogen. While idealized responses do occur in nature, the most interesting and productive ends of the T cell research spectrum focus on what happens when things go wrong and why. Examining these extremes of immune dysfunction, within the framework of an idealized response, promises to be a fruitful future source of investigation with both basic and clinical relevance.