Murine malaria: dissociation of natural killer (NK) cell activity and resistance to Plasmodium chabaudi.

Striking differences in the resistance to P. chabaudi infection among different inbred mouse strains have previously been correlated with the level of both the spontaneous and the infection-induced enhanced level of NK cell activity. We have examined this putative correlation in individual animals of backcross progeny derived from A/J (malaria-susceptible, low NK cell activity) and B10.A (malaria-resistant, high NK cell activity) progenitors. We have found that NK cell activity and resistance to malaria segregated independently. Furthermore, C57BL/6-bg/bg mice which are deficient in NK cell activity were found to be as resistant to malaria as their heterozygous C57BL/6-bg/+siblings. We conclude that low NK cell activity, characteristic of A/J strain mice, is not a sufficient determinant of the exquisite susceptibility of these animals to infection with Plasmodium chabaudi.