T cell response to N-formylated peptides in humans

We present the first evidence of a T lymphocyte response to N-formylated pe ptides in humans. N-formylated peptide sequences from self (mitochondrial) and foreign (microbial) antigens were used to isolate antigen-specific T ce ll clones from healthy individuals, including a set of monozygotic twins. T he observed response differed from that previously described in mouse (CD4( +) phenotype and MHC class II restriction in humans vs. CD8(+) phenotype an d class I restriction in mice). These lymphocytes produce substantial amoun ts of IFN-gamma. They were isolated in only one of the monozygotic twins, w hich suggests that their expansion in the healthy immune repertoire is inde pendent of the genetic background. Our result will help in assessing the re levance of N-formylated peptide-specific T cells in protection against infe ctions within the human immune system.