Given the presented data and previous findings from others and our laboratory highlighting the importance of MΦ in controlling rickettsiae infection (22, 24, 31, –, 34), we sought to determine the contributing role of MΦ in the observed susceptibility difference between R. typhi- or R. rickettsii-infected CD300f-/- and WT mice. The gene discussed is CD300LF; the disease is Rickettsiosis.