<prompt> Nichols strain is used in:TP HA testTPI testVDRLFTA-ABS  <response>: Treponema pallidum immobilization TPI test, considered both as a qualitative and as a quantitative test, and then various specific aspects of passage of the Nichols strain of treponeme in rabbit testes. a serological test for syphilis in which a solution containing the living causative spirochete Treponema pallidum is combined with serum in the presence of complement with immobilization of the active spirochetes indicating a positive result 