Activation and suppression of T cells in termination of immunological tolerance.

Immunological tolerance was induced in adult C3H mice by five injections of ultra-centrifuged, soluble HSA at weekly intervals. The tolerant state was readily terminated by the challenge immunization with slightly sulphanilated HSA administered as Freund's complete adjuvant emulsion. In this case, it was shown that T cells specific for HSA were activated which could serve as helpers for the production of anti-hapten antibodies. The tolerance termination and activation of T cells specific for HSA was not observed in the profound tolerant state, induced by nine injections of ultra-centrifuged, soluble HSA at weekly intervals, where suppressor T cells were detected. Implications of these results were discussed in reference to the development of autoimmunity.