CD4 + T-Cell Subsets That Mediate Immunological Memory to Mycobacterium tuberculosis Infection in Mice

Abstract

ABSTRACT We have studied CD4 + T cells that mediate immunological memory to an intravenous infection with Mycobacterium 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 (<20 h) and expressed high levels of intracellular gamma interferon and the T-cell activation markers CD69 and CD25. These memory effector T cells expressed intermediate levels of CD45RB and were heterogeneous with regard to the L-selectin and CD44 markers. By adoptive transfer into nude mice, the highest level of resistance to a challenge with M. tuberculosis was mediated by CD45RB high , l -selectin high , CD44 low cells. 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 against M. tuberculosis .