Similar responses by macrophages from young and old mice infected with Mycobacterium tuberculosis.

The growth of four isolates of Mycobacterium tuberculosis was compared in cultures of bone marrow-derived macrophages generated from young (3 months) and old (24 months) female C57BL/6 mice. In all four cases, no differences were seen in the course of the in vitro infection over a 10-day culture period. Macrophages from both young and old mice secreted similar levels of nitric oxide if treated with interferon gamma (IFN) 24 h prior to infection. Expression of mRNA encoding an array of early response genes in the two sets of cultures was also generally similar. These data indicate that the capacity of macrophages to respond to infection with a virulent intracellular bacterial infection does not seem to be influenced by the increasing age of the host.