Analysis of HLA–ABC locus-specific transcription in normal tissues

We developed a novel human leukocyte antigen HLA–ABC locus-specific quantitative real-time polymerase chain reaction (PCR) to determine the locus-specific gene expression of HLA–ABC in peripheral blood leukocytes (PBLs, n = 53), colon mucosa (n = 15), and larynx mucosa (n = 15). Laser-assisted tissue microdissection allowed us to study the selected cells without interference from surrounding stroma. We report evidence on the specificity of the technique, describing the HLA–ABC locus-specific gene expression patterns found in the PBLs and two solid tissues studied. PBLs showed a higher gene expression of HLA-B than of HLA-A or HLA-C (p = 4.7 × 10−10 and p = 1.6 × 10−6, respectively). In solid tissue, HLA-A and HLA-B gene expressions were similar and HLA-C expression lower. In particular, in larynx mucosa, significant differences were found between HLA-A and HLA-C expressions and between HLA-B and HLA-C expressions (p = 6.5 × 10−4 and p = 8.1 × 10−4, respectively). The same differences were observed in colon mucosa, but significance was not reached (p = 0.08 and p = 0.06, respectively). Differences in locus-specific regulation may be related to the control of cytotoxic responses of NK and CD8 positive T cells. Gene expression of HLA–ABC specific locus showed no intra-individual variability, but there was a high inter-individual variability. This may result from differences in the expression of common regulatory factors that control HLA–ABC constitutive expression.