Several recent studies have begun to shed light on ehrlichial immunopathogenesis, with infection of human macrophage cell lines resulting in transcriptional alterations associated with down-regulated macrophage function [24], with production of dysfunctional cytotoxic TNFα by CD8 T lymphocytes [21], or by direct stimulation of NKT cells to produce excessive quantities of IFNγ [25]. This evidence concerns the gene TNF and infection.