Passive immunization does not provide protection against experimental infection with Mycoplasma haemofelis

Sugiarto, Sarah; Spiri, Andrea M.; Riond, Barbara; Novacco, Marilisa; Oestmann, Angelina; de Miranda, Luisa H. Monteiro; Meli, Marina L.; Boretti, Felicitas S.; Hofmann-Lehmann, Regina; Willi, Barbara

In the individual cats, the decrease in leukocyte, lymphocyte and neutrophil counts occurred just prior to the development of anemia and the onset of peak bacteremia. A similar pattern was also observed for the eosinophils, whereas the monocyte counts peaked at the onset of maximal anemia. A decrease in leukocyte and neutrophil counts could be caused by the increased consumption of these cells, which are involved in bacterial killing or, less likely, by reduced production due to undefined inhibitory factors [47] . Monocytosis could be found due to hemolysis [48] and was shown to be associated with Mhf infection in naturally infected cats [49] . We documented leukopenia and neutropenia, as well as decreased eosinophils, lymphocytes and increased monocytes, at times of peak Mhf bacteremia also in a recent study [15] . It is difficult to judge whether the decrease in the white blood cell subsets was due to bacterial replication and cell consumption or, conversely, whether the decrease in white blood cells facilitated bacterial replication.