Mycoplasma pulmonis infection augments natural killer cell activity in mice

The goal of this study was to determine if experimental Mycoplasma pulmonis infection augmented splenic natural killer (NK) cell activity in mice. A 4 hour 51Cr-release in vitro assay using YAC-1 tumor target cells was employed to measure splenic NK cell activity in C57BL/6J mice infected intraperitoneally with M. pulmonis and in uninfected controls. Transient augmentation of the NK cells was observed, peaking at day 3 postinoculation (PI) and gradually returning to normal levels by day 10 PI. Selective depletion studies showed that the cells responsible for killing target cells were NK cells. They were nonadherent to nylon wool, not susceptible to Thy-1.2 antibody and susceptible to asialo GM1 ganglioside antibody. Inadvertent augmentation of the NK cell system due to M. pulmonis infection may complicate the interpretation of research data, especially in immunology and cancer studies.