The ability to learn and remember previously encountered pathogens is a hallmark of the vertebrate immune system. CD8+ T cells, called central memory cells (TCM), mediate much more rapid and vigorous immune responses against the viruses that they recognize compared to their uneducated precursors, the naive T cells (TN). In this issue, Sung et al. (pp. 1249–1263) compare, at the single-cell level, the response of TN and TCM to a subcutaneous viral challenge. The invading virions are rapidly transported to the draining lymph nodes, where they infect macrophages that line the periphery of these bean-shaped organs. The image shows a cross-section of a lymph node in which virus-infected macrophages are identified by their yellow-green color. Initially, both TN and TCM reside in the deep T cell area (the dark region in the center of the organ). TCM, unlike TN, expresses CXCR3, a chemokine receptor that enables TCM to sense distant viral infections and to migrate peripherally between the B cell follicles (red) and into the medulla (the blue-green region on the left). This chemokine-dependent redistribution of TCM provides rapid access to viral antigen, which is critical for expedient clearance of the virus and, thus, represents a key molecular feature of immunological memory.
Oil on canvas painting by Meghan Perdue.
