Molecular characterization of T cell receptor beta variable in the peripheral blood T cell repertoire in subjects with active tuberculosis or latent tuberculosis infection

Abstract

Background: T cells are closely linked to the clinical manifestations of subjects with Mycobacterium tuberculosis (MTB) infection. T cell receptor beta variable (TCRBV) is a signal and indicative molecule on the membrane of T lymphocytes, reflecting the composition and specificity of T cells. The molecular profiles of TCRBV in peripheral blood mononuclear cells (PBMCs) and their subpopulations (CD4+ and CD8+ T cells) from subjects with active tuberculosis (TB) or latent TB infection (LTBI) have not been well described.

Methods: In 42 subjects with active TB or LTBI, PMBCs and their subsets were separated and sorted. The molecular profiles of the TCRBV complementarity determining region 3 (CDR3) in the three cell populations were investigated using our recently developed gene melting spectral pattern (GMSP) assay. The TCRBV members were then cloned and sequenced when their GMSP image profiles showed a single-peak.

Results: The average number of skewed TCRBV molecules in the CD4+ cell subset was significantly higher than that in PBMCs and CD8+ T cells. TCRBV12, BV13.1, BV13.2, and BV24 were expressed more prevalently than other TCRBV gene families in the three cell populations. In addition, relatively conserved amino acid motifs were identified in TCRBV5.1 and BV20 CDR3 in PBMCs and its subsets. The monoclonal TCRBV14 and BV23 expressed were different between active TB and LTBI subjects.

Conclusions: These results indicate that the T cell immune response is complex and multi-specific in active TB and LTBI subjects. Analysis of TCRBV expression in CD4+ T cells suggest that it could be useful in assessing the composition and status of circulating T cells. Furthermore, the expression of TCRBV14, BV23 and the sequencing of CDR3 amino acid motifs of TCRBV5.1, BV20 could be used in the differential diagnosis and treatment of subjects with active TB or LTBI.

Figure 1

Comparing the number of skewed TCRBV family between CD4⁺ and CD8⁺ T cell subsets in active TB patients. Values are means ± STD. **P <0.01. CD4⁺ cell, purified CD4⁺ T lymphocytes; CD8⁺ cell, purified CD8⁺ T lymphocytes.

Figure 2

Comparing the number of skewed TCRBV family between CD4⁺ and CD8⁺ T cell subsets in LTBI individuals. Values are means ± STD. **P <0.01. CD4⁺ cell, purified CD4⁺ T lymphocytes; CD8⁺ cell, purified CD8⁺ T lymphocytes.

Figure 3

Relative frequency of each TCRBV family in active TB or LTBI subjects. TCRBV family in PBMCs derived from active TB patients or LTBI individuals were shown as open bars or filled bars respectively. Data are presented as % expression of each TCRBV family relative to the total expression of all 24 TCRBV genes (1 ~ 24). The data represent the means and standard deviation. **P <0.01.