Diverse T-cell receptor CDR3 length patterns in human CD4+ and CD8+ T lymphocytes from newborns and adults

T cells are essential in the initiation and maintenance of immune responses. Specific interaction between T cells and a presumptive antigen occurs through recognition of an MHC-peptide complex by the T-cell receptor (TCR). The complementarity-determining region (CDR) 3 of the TCR has direct contact with the peptide. Here we describe CDR3 length variability of six different TCRBV gene families of CD4(+) and CD8(+) umbilical cord (UC) and peripheral blood (PB) T cells. Amplified products spanning the TCR CDR3 regions from CD4(+) PB, CD4(+) UC and CD8(+) UC blood T cells typically displayed Gaussian-like distributions. In contrast, profound and frequent perturbations were recorded in CD8(+) PB lymphocytes, with a non-Gaussian pattern in more than half of the samples studied. A substantial portion of the perturbed CD8(+) subsets were clonal or oligoclonal, as determined by CDR3-length restriction, TCRBJ gene usage and nucleotide sequencing. This implies that the conditions for shaping and maintenance of the peripheral TCR repertoire are profoundly different for CD8(+) and CD4(+) T cells.