Mutant HLA-A2 antigens as restricting elements for virus-specific cytotoxic T cells

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• Human Leukocyte Antigen (HLA) molecules are crucial for T cell recognition and immune response.
• The Epstein-Barr virus (EBV) transformed cell line T5-1 expresses specific HLA antigens, including HLA-A2.
• Mutations in HLA genes can alter antigen presentation and immune surveillance.

Purpose of the Study:

• To investigate the impact of experimentally induced mutations in HLA-A2 antigen structure on T cell-mediated cytolysis.
• To determine if alterations affecting serological recognition also affect T cell restriction sites.
• To compare experimentally induced HLA-A2 mutations with naturally occurring variants.

Main Methods:

• Utilized EBV-transformed T5-1 cell line mutants with characterized alterations in HLA-A2 expression.
• Employed HLA-A2-specific monoclonal antibody BB7.2 to assess HLA-A2 surface expression.
• Tested susceptibility to cytolysis using EBV-specific effector T cells restricted through HLA-A2 and HLA-B27 antigens.

Main Results:

• Parent T5-1 cells were susceptible to lysis by both HLA-A2 and HLA-B27 restricted T cells.
• T5-1 mutants with reduced HLA-A2 expression were resistant to HLA-A2 restricted T cell lysis.
• Mutants expressing altered HLA-A2 molecules, recognized differently by antibody BB7.2, remained susceptible to HLA-A2 restricted lysis.
• All T5-1 mutant lines were susceptible to HLA-B27 restricted cytolysis.

Conclusions:

• Experimentally induced mutations affecting serologically defined sites on HLA-A2 do not necessarily alter T cell-restricting determinants.
• This finding contrasts with naturally occurring HLA-A2 variants, which often exhibit changes at T cell-restricting sites.
• The study highlights the distinct nature of experimentally induced versus naturally occurring HLA antigen mutations in immune recognition.