Isolation of a human T cell line specific for a streptococcal cell surface antigen

Area of Science:

• Immunology
• Microbiology
• Molecular Biology

Background:

• Streptococcus mutans is a key pathogen in dental caries.
• The cell surface antigen SAI/II (Mr 185,000) from S. mutans has been previously characterized.
• Understanding immune responses to specific bacterial antigens is crucial for vaccine development.

Purpose of the Study:

• To isolate and characterize a T cell line specific for the S. mutans antigen SAI/II.
• To investigate the specificity and phenotype of the isolated T cell line.
• To determine the HLA restriction of the T cell response to SAI/II.

Main Methods:

• Isolation of a T cell line from peripheral blood mononuclear cells (PBMC) of a naturally sensitized individual.
• Maintenance of the T cell line in culture.
• Testing specificity against native and recombinant SAI/II, and a homologous antigen (SpaA) from Strep. sobrinus.
• Flow cytometry for T cell phenotype analysis (CD3, CD4, CD8, TcR alpha beta).
• HLA typing and inhibition studies for class II restriction.

Main Results:

• A T cell line specific for native SAI/II was successfully isolated and maintained.
• The T cell line showed high specificity for both native and recombinant SAI/II.
• No response was observed to the homologous antigen SpaA from Strep. sobrinus.
• The T cell line exhibited a CD3+ CD4+ CD8- TcR alpha beta + phenotype.
• T cell response was restricted by both DR and DP encoded class II molecules.

Conclusions:

• A specific T cell line targeting the S. mutans antigen SAI/II has been established.
• This T cell line provides a valuable tool for studying cellular immunity against S. mutans.
• The findings highlight the role of HLA class II (DR and DP) in restricting T cell recognition of SAI/II.