Direct evidence that functionally impaired CD4⁺ T cells persist in vivo following induction of peripheral tolerance

A small population of CD4⁺ OVA-specific TCR transgenic T cells was tracked following the induction of peripheral tolerance by soluble Ag to address whether functionally unresponsive, or anergic T cells, persist in vivo for extended periods of time. Although injection of OVA peptide in the absence of adjuvant caused a transient expansion and deletion of the Ag- specific T cells, a population that showed signs of prior activation persisted in the lymphoid tissues for several months. These surviving OVA- specific T cells had long-lasting, but reversible defects in their ability to proliferate in lymph nodes and secrete IL-2 and TNF-α in vivo following an antigenic challenge. These defects were not associated with the production of Th2-type cytokines or the capacity to suppress the clonal expansion of a bystander population of T cells present in the same lymph nodes. Therefore, our results provide direct evidence that a long-lived population of functionally impaired Ag-specific CD4⁺ T cells is generated in vivo after exposure to soluble Ag.