Influence of Bordetella pertussis and bacterial endotoxins on the immunological reactivity of germfree mice.

As compared to specifically pathogen-free NMRI mice, in principle, the immunological reactivity of germfree mice of the same strain and age was not found to be reduced. This is documented by the cellular kinetics of the primary immune responses, evoked by the intraperitoneal (i.p.) injection of either a "saturated" dose of 4 times 10(8) sheep erythrocytes (SE) or the simultaneous injection of 4 times 10(8) SE and 3 times 10(9) killed Bordetella pertussis organisms (PO). Thereby, adjuvancy of PO was not found to be reduced in germfree mice. The only difference consisted in the demonstration of significantly reduced numbers of both direct and indirect plaque-forming spleen cells (PFC) on the 4th day after primary antigenic stimulation. This is suggested to be due to a lack of sufficient training of the immunological apparatus of germfree mice. Both in germfree and conventional mice significant splenomegaly, blood leukocytosis as well as increase in the numbers of pre-existing "background" PFC became detectable following a single i.p. injection of 3 times 10(9) PO without SE. Similarly, the injection of endotoxin from Serratia marcescens produced a moderate increase in the numbers of "background" PFC. From the data presented it is suggested that strict gnotobiotic conditions do not cause noteworthy deficiency in immunological competence.