Class I HLA haplotypes form two schools that educate NK cells in different ways

Area of Science:

• Immunology
• Genetics
• Cell Biology

Background:

• Natural killer (NK) cells are crucial lymphocytes for innate and adaptive immunity, and placental reproduction.
• Their function is regulated by receptors recognizing HLA class I molecules on tissue cells.
• Killer cell immunoglobulin-like receptors (KIR) and the CD94:NKG2A receptor interact with HLA class I and HLA-E, respectively.

Purpose of the Study:

• To investigate the impact of a specific dimorphism in the HLA-B leader sequence (-21M/T) on NK cell receptor ligand expression and NK cell function.
• To understand the genetic control and evolution of NK cell receptor ligands encoded by HLA haplotypes.

Main Methods:

• Analysis of human population genetics to correlate HLA-B allotypes with KIR and HLA-E ligand expression.
• Utilizing mass cytometry and immune function assays to assess NK cell education, phenotype, and potency in different genetic groups.

Main Results:

• A methionine/threonine dimorphism at position -21 of the HLA-B leader sequence (-21M/T) divides the human population into M/M, M/T, and T/T groups.
• Individuals with M/M and M/T genotypes show preferential CD94:NKG2A ligand supply, leading to better-educated, more diverse, and functionally potent NK cells compared to T/T individuals.
• HLA haplotypes are broadly categorized into those favoring CD94:NKG2A ligands or KIR ligands, influenced by the -21M/T dimorphism.

Conclusions:

• The -21 HLA-B dimorphism significantly impacts NK cell immunity by shaping the repertoire of NK cell receptor ligands.
• This genetic variation leads to distinct NK cell education and functional outcomes across different human populations.
• Findings provide new insights into the evolution of HLA-encoded NK cell ligands and suggest novel approaches for studying HLA class I associations in clinical settings.