CD4+T-Cell Subsets That Mediate Immunological Memory toMycobacterium tuberculosisInfection in Mice

Abstract

We have studied CD4⁺T cells that mediate immunological memory to an intravenous infection withMycobacterium tuberculosis. The studies were conducted with a mouse model of memory immunity in which mice are rendered immune by a primary infection followed by antibiotic treatment and rest. Shortly after reinfection, tuberculosis-specific memory cells were recruited from the recirculating pool, leading to rapidly increasing precursor frequencies in the liver and a simultaneous decrease in the blood. A small subset of the infiltrating T cells was rapidly activated (M. tuberculosiswas mediated by CD45RB^high,l-selectin^high, CD44^lowcells. Taken together, these two lines of evidence support an important role for memory cells which have reverted to a naive phenotype in the long-term protection againstM. tuberculosis.