Natural immunity to murine gonococcal bacteremia: roles of complement, leucocytes, and sex

The roles of the serum bactericidal system, inflammatory cells, and sex in resisting gonococcal infection were studied in a murine model of gonococcal bacteremia. The role of serum killing in defense was investigated with complement component 5 deficient (C5-deficient) (B1O.D2/OSN) and normal (B1O.D2/NSN) mice. No significant differences were found between LD50's with either murine serum-sensitive or serum-resistant gonococci in those two mouse strains. However, in vitro experiments revealed a heat-stable factor in mouse serum which killed gonococci. Thus it appeared that the C5-deficient mouse is not a good model for the study of the role of C-mediated killing in resistance to gonococcal infection. Mice with Chediak-Higashi disease were used to study the role of phagocytes and natural killer cells. The difference in LD50's between affected mice (C57B1/6J beige J) and controls (C57B1/6J) was significant. The CBA/N mice, which have a B-cell maturation defect, were no more resistant to infection than control mice, which was taken as further evidence that B cells were less important than other leucocytes in innate immunity to gonococcal infection. Finally, male mice were significantly more resistant than female mice to gonococcal bacteremia. Thus, in this study the two most important determinants of resistance to gonococcal infection were inflammatory cells and sex.