Previously fatal murine ehrlichiosis due to HF strain (derived from infected mouse spleen homogenate) infection is associated with T cell-mediated tissue damage, high levels of serum TNF-α and IL-10, and CD4-Th1 hyporesponsiveness (Stevenson et al., 2008), which are associated with liver pathology and failure to clear HF strain in mice (Ismail et al., 2004). The gene discussed is CD4; the disease is hydrops fetalis.