Specific binding of antigen onto human T lymphocytes

Area of Science:

• Immunology
• Molecular Biology
• Microbiology

Background:

• Human T lymphocytes can be sensitized to Candida albicans (CA).
• Mannan, a polysaccharide from CA's cell wall, induces T lymphocyte proliferation.
• The mechanism of T cell recognition of mannan is not fully understood.

Purpose of the Study:

• To investigate the direct binding of mannan to human T lymphocytes.
• To characterize the receptor involved in mannan binding on T cells.
• To explore the potential role of T cell receptor (TCR) and HLA-DQ in mannan recognition.

Main Methods:

• Using radiolabeled [3H]mannan to detect binding to T lymphocytes.
• Testing specificity by using irrelevant blast cells and a different polysaccharide (SIII).
• Investigating binding characteristics (reversibility, saturation) and inhibition using monoclonal antibodies (anti-T3, anti-HLA-DQ).

Main Results:

• Antigen-specific T blast cells demonstrated specific binding of [3H]mannan.
• Mannan binding was found to be reversible and saturable.
• Binding was inhibited by anti-T3 antibodies, suggesting TCR involvement, and partially by anti-HLA-DQ antibodies.

Conclusions:

• Human T lymphocytes directly bind mannan from Candida albicans.
• The T cell receptor (TCR) is likely involved in recognizing mannan.
• Mannan recognition may involve TCR cross-linking or association with HLA-DQ molecules.