TABLE 1.

Immunity correlates with serum treponemicidal activity and TROMP aggregation

Rabbit serum (n)	Immune statusa	TEb	OM fracture-face observations	Total no. of particles/μm2	% Aggregationc
Group A (17)	Susceptible	≤1:1	24	54	16.5 ± 5.6
Group B (17)	Partial	1:16	20	41	18.9 ± 6.5
Group C (16)	Complete	1:128	20	79	88.6 ± 5.4d
Normal	Susceptible	0	21	48	13.4 ± 4.2
Immune	Complete	1:128	20	53	53.9 ± 7.8d

^aImmune status of infected, treated, and challenged rabbits. Susceptible, dark-field microscopy-positive lesions and disseminated infection; partial, dark-field microscopy-negative lesions and no disseminated infection; complete, no lesions or disseminated infection. 

^bThe TE was determined as the final serum dilution which immobilized ≥50% of a treponemal suspension incubated for 16 h in the presence of complement. 

^cPercent aggregation (mean ± standard error) was determined from the number of aggregates consisting of two or more particles and the total number of particles counted. 

^dP < 0.0001, compared with the results for the susceptible animals and normal control animals.