Interactions of HLA-B*4801 with peptide and CD8

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• Human Leukocyte Antigen (HLA) class I molecules present peptides to T cells, crucial for immune responses.
• The B*4801 allotype's specific functional characteristics and interactions with co-receptors are not fully understood.

Purpose of the Study:

• To investigate the peptide binding specificity of the B*4801 allotype.
• To determine the interaction of B*4801 with CD8 alpha homodimers and its functional implications.

Main Methods:

• Transfection of HLA class I-deficient 221 cells with B*4801 cDNA.
• Pool sequence analysis of endogenously bound peptides.
• In vitro cell-cell binding assays using wild-type and mutant B*4801.
• Analysis of T-cell inhibition by anti-CD8 monoclonal antibodies.
• Genomic analysis of B*48 alleles in diverse populations.

Main Results:

• B*4801 selects nonamer peptides with glutamine or lysine at position 2 and leucine at the carboxyl-terminus.
• A threonine residue at position 245 in the alpha 3 domain of B*4801 causes weak binding to CD8 alpha homodimers.
• A mutant B*4801 with alanine at position 245 exhibits comparable CD8 alpha binding to other HLA class I allotypes.
• Despite weak CD8 alpha affinity, T-cell recognition of B*4801 is inhibited by anti-CD8 antibodies.
• Threonine 245 is conserved across all analyzed B*48 alleles.

Conclusions:

• The B*4801 allotype has a defined peptide binding motif and a unique interaction with CD8 alpha mediated by threonine 245.
• The conserved threonine 245 residue influences B*4801's functional properties, including its interaction with T-cell co-receptors.
• Understanding these interactions is vital for comprehending HLA class I-restricted T-cell responses and potential immune evasion mechanisms.