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Cell response in rabbits infected with T. pallidum as measured by the leucocyte migration inhibition test
Abstract:
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.
Insights
Leukocyte migration assays reveal a biphasic immune response to syphilis infection in rabbits. Early infection stimulates migration, while later stages show inhibition, independent of antibody levels.
Area of Science:
- Immunology
- Microbiology
- Infectious Diseases
Background:
- Syphilis, caused by *Treponema pallidum* (T. pallidum), is a complex infectious disease.
- Understanding the host immune response, particularly cellular immunity, is crucial for diagnosis and treatment.
- Leukocyte migration inhibition assays are used to assess cellular immune responses in vitro.
Purpose of the Study:
- To investigate the cellular immune response to *T. pallidum* infection in a rabbit model.
- To evaluate the correlation between *in vitro* leukocyte responses and *in vivo* immune status.
- To examine the effect of different antigen concentrations on leukocyte migration.
Main Methods:
- Leukocyte migration inhibition assay in agarose was performed on peripheral blood leukocytes from 48 rabbits infected with *T. pallidum*.
- Cells were exposed to *T. pallidum* antigen (TpAg), Reiter antigen (RAg), and VDRL reagent.
- Intradermal skin tests with heat-killed *T. pallidum* were conducted to correlate with *in vitro* findings.
Main Results:
- A biphasic leukocyte migration pattern was observed: stimulation in early infection (up to 4 weeks) and inhibition in later stages.
- Higher concentration of TpAg (15 µg/ml) consistently inhibited leukocyte migration.
- No correlation was found between *in vitro* cellular responses and treponemal antibody levels or intradermal skin test results.
Conclusions:
- Leukocyte migration assays demonstrate a dynamic cellular immune response to *T. pallidum* infection in rabbits.
- The observed biphasic response suggests a shift in immune cell function during the course of syphilis.
- Cellular immune responses, as measured by migration assays, may not directly correlate with humoral immunity or skin test reactivity in this model.
