Human T-cell receptor BV6 gene polymorphism in relation to expression level and CD4/CD8 skewness

Area of Science:

• Immunology
• Genetics

Background:

• T-cell receptor beta variable (TCRBV) genes play a crucial role in adaptive immunity.
• Understanding the polymorphism and expression patterns of TCRBV genes, such as BV6S4 and BV6S5, is vital for elucidating T-cell repertoire diversity and function.

Purpose of the Study:

• To investigate the polymorphism, usage frequencies, and CD4/CD8 T-cell skewness of human T-cell receptor beta variable (TCRBV) genes BV6S4 and BV6S5 in Japanese umbilical cord blood lymphocytes.
• To determine the association between specific genotypes and alleles of BV6S4 and BV6S5 with their expression levels and T-cell subset distribution.

Main Methods:

• Analysis of 50 Japanese umbilical cord blood lymphocyte samples.
• Genotyping of TCRBV genes BV6S4 (alleles A1, A2, A3) and BV6S5 (alleles A1, A2).
• Assessment of gene usage frequencies and CD4/CD8 T-cell skewness for different genotypes and alleles.

Main Results:

• BV6S4 and BV6S5 exhibited contrasting CD4/CD8 skewness, with BV6S4 favoring CD8+ T cells and BV6S5 favoring CD4+ T cells.
• Two BV6S4 genotypes (A1/A2, A2/A2) were identified, showing no significant differences in usage or skewness.
• All three BV6S5 genotypes (A1/A1, A1/A2, A2/A2) were observed, with gene usage frequency correlating with genotype (A1/A1 > A1/A2 > A2/A2), suggesting amino acid substitutions influence expression.
• BV6S5 A1 alleles were expressed more frequently than A2 alleles in both CD4+ and CD8+ T cells, but this did not correlate with an increased CD4+ T-cell ratio.

Conclusions:

• Amino acid substitutions in BV6S5 are associated with its expression level.
• While BV6S5 shows a bias towards CD4+ T cells, the higher expression of A1 alleles is not linked to an increased proportion of CD4+ T cells.
• These findings contribute to understanding T-cell receptor repertoire variability and its genetic underpinnings in different T-cell subsets.