A multicomponent system for generating a population of engineered TCR-presenting cells (eTPC-t), for use in discovery and characterisation of TCRs and T-cell antigens comprising a first component which is an engineered TCR-presenting cell (eTPC), designated component A, wherein component A lacks endogenous surface expression of at least one family of analyte antigen-presenting complexes (aAPX) and/or analyte antigenic molecule (aAM)wherein the lack of surface expression is selected as to minimise interference in matched analyses of target analyte antigens , lacks endogenous expression of TCR chains alpha, beta, delta and gamma, and expresses CD3 proteins and contains two further single components designated B and D, which are different and each respectively a genomic receiver site for integration of a single ORF encoding at least one analyte TCR chain of alpha, beta, delta or gamma, and/or two ORFs encoding a pair of analyte TCR chains, and wherein the genomic receiver sites B and D are each selected from a. A synthetic construct designed for recombinase mediated cassette exchange (RMCE) b. A synthetic construct designed for site directed homologous recombination; and a second component is a genetic donor vector, designated component C, for site directed integration of ORF encoding analyte TCR chains, wherein component C, is matched to component B, and wherein the component C is designed to deliver c. A single ORF encoding at least one analyte TCR chain of alpha, beta, delta and/or gamma and/or d. Two ORFs encoding a pair of analyte TCR chains. and wherein c and/or d optionally encodes a selection marker of integration, such that the analyte TCR chains can be expressed as TCR surface protein in complex with the CD3 (TCRsp) on component A. a first component which is an engineered TCR-presenting cell (eTPC), designated component A, wherein component A lacks endogenous surface expression of at least one family of analyte antigen-presenting complexes (aAPX) and/or analyte antigenic molecule (aAM)wherein the lack of surface expression is selected as to minimise interference in matched analyses of target analyte antigens , lacks endogenous expression of TCR chains alpha, beta, delta and gamma, and expresses CD3 proteins and contains two further single components designated B and D, which are different and each respectively a genomic receiver site for integration of a single ORF encoding at least one analyte TCR chain of alpha, beta, delta or gamma, and/or two ORFs encoding a pair of analyte TCR chains, and wherein the genomic receiver sites B and D are each selected from a. A synthetic construct designed for recombinase mediated cassette exchange (RMCE) b. A synthetic construct designed for site directed homologous recombination; and a. A synthetic construct designed for recombinase mediated cassette exchange (RMCE) b. A synthetic construct designed for site directed homologous recombination; a second component is a genetic donor vector, designated component C, for site directed integration of ORF encoding analyte TCR chains, wherein component C, is matched to component B, and wherein the component C is designed to deliver c. A single ORF encoding at least one analyte TCR chain of alpha, beta, delta and/or gamma and/or d. Two ORFs encoding a pair of analyte TCR chains. and wherein c and/or d optionally encodes a selection marker of integration, such that the analyte TCR chains can be expressed as TCR surface protein in complex with the CD3 (TCRsp) on component A. c. A single ORF encoding at least one analyte TCR chain of alpha, beta, delta and/or gamma and/or d. Two ORFs encoding a pair of analyte TCR chains. <EOS>