![]() The region of TCR-β that spans the V-D and D-J junctions, known as "complementarity determining region 3" (CDR3), is unique to each TCR-β variant and is frequently used to quantify TCR diversity in high-throughput profiling experiments. Ultimately, this process-commonly referred to as "V(D)J recombination"-yields a population of T cells with sufficient TCR diversity to collectively recognize any peptide imaginable. T-cell progenitors are derived from hematopoietic stem cells (HSCs) in the thymus, and as these cells divide, extensive recombination occurs between the V- and J-segments, and the V-, D-, and J-segments, in the TCR-α and TCR-β genes, respectively, via a mechanism that also incorporates and deletes additional nucleotides (Figure 1, Panel B). TCR diversity is generated during the early stages of T-cell development. The term "clonotype" is typically used to refer either to a particular TCR variant (TCR-α or TCR-β subunit) or to a particular pairing of TCR subunit variants (TCR-α + TCR-β) shared among a clonal population of T cells. The vast majority of TCRs are heterodimers composed of two distinct subunit chains (α- and β-), which both contain variable domains and, in humans, are encoded by single-copy genes. To this end, the adaptive immune system has evolved a system for somatic diversification of TCRs that is unrivaled in all of biology. ![]() Given the relative specificity of TCR-antigen interactions, a tremendous diversity of TCRs are required to recognize the wide assortment of pathogenic agents one might encounter. Antigen recognition by TCRs activates T cells, causing them to proliferate rapidly and mount immune responses through the release of cytokines. Essential to T-cell function are highly specialized extracellular receptors (T-cell receptors or TCRs) that selectively bind specific antigens displayed by major histocompatibility complex (MHC) molecules on the surface of antigen-presenting cells (APCs) (Figure 1, Panel A). In humans and closely related species, cellular immunity is mediated by T cells (or T lymphocytes), which participate directly in the detection and neutralization of pathogenic threats. The ability to easily and reliably obtain comprehensive portraits of human T-cell repertoires will accelerate the fulfillment of basic and applied research objectives and could provide a basis for the development of novel clinical diagnostic solutions. The unparalleled sensitivity afforded by this approach allows for the detection of low-abundance TCR variants from small sample inputs of human peripheral blood RNA or purified human T cells, and the avoidance of multiplex PCR minimizes the likelihood of sample misrepresentation due to amplification biases. ![]() 635014, 635015, 635016), a high-throughput method for TCR mRNA profiling that leverages SMART ( Switching Mechanism at the 5′ end of RNA Template) technology and semi-nested PCR to fully capture and amplify variable regions of TCR-α and TCR-β subunits and prepare libraries for sequencing on Illumina platforms. Here we present the SMARTer Human TCR a/b Profiling Kit (Takara Bio, Cat. Remarkable sensitivity and reproducibilityĬlonotype-specific sequences present at a concentration of 0.1% are detectable above background. ![]()
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