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.