M3-Restricted T Cells May Be Critical For Immune Response To TB.(Brief Article)

2001 AUG 8 - (NewsRx.com & NewsRx.net) --

by N.R. Saltmarsh, staff medical writer - Data about Mycobacterium tuberculosis (Mtb) epitopes recognized by class Ib-restricted T cells is limited, but researchers now believe one of the Ib-restricted molecules, M3, may participate in the immune response to Mtb infection.

The findings of T. Chun and colleagues at the University of Chicago have implications for Mtb vaccine development.

"M3 is an MHC class Ib molecule that preferentially presents N-formylated peptides to CD8(+) T cells, explained Chun and coworkers. "Because bacteria initiate protein synthesis with N-formyl methionine, the unique binding specificity of M3 makes it especially suitable for presenting these particular bacterial epitopes."

After scanning the full sequence of the Mtb genome for NH2-terminal peptides that shared features with other M3-binding peptides, Chun and team tested synthetic peptides for their ability to bind to M3 in an immunofluorescence-based peptide-binding assay.

Four of the N-formylated Mtb peptides could elicit cytotoxic T lymphocytes (CTLs) from mice immunized with peptide-coated splenocytes, they reported. The Mtb peptide-specific, M3-restricted CTLs lysed the Mtb-infected macrophages effectively, suggesting that these N-formylated Mtb peptides are presented as the naturally processed epitopes by Mtb-infected cells, the researchers noted.

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