Cell response in rabbits infected with T. pallidum as measured by the leucocyte migration inhibition test.

Leucocyte migration in agarose was used to examine cell response in 48 rabbits infected with the Nichols strain of T. pallidum for 1 week to 16 months. The response of the peripheral leucocytes to T. pallidum antigen (TpAg), 3 and 15 mug/ml., Reiter antigen (RAg) 6 mug./ml., and VDRL reagent 1:500 was examined. The cells in the presence of RAg, TpAg--3 mug./ml.--and the VDRL reagent demonstrated a biphasic response; in the early stage of infection (until the 4th week) stimulation of leucocyte migration and in the later stage of disease inhibition of leucocyte migration was observed. The higher concentration of TpAg--15 mug./ml.--caused only inhibition of leucocyte migration. The leucocyte response in vitro could not be confirmed by intradermal skin tests with 5 x 10(7) heat-killed T. pallidum. No correlation between the cell response and the treponemal antibodies was observed.