%0 Journal Article
%T Differential T-Cell Receptor Signaling: A Novel Paradigm for Thymic Selection and Lineage Commitment
%A Yasir Arafat Maassoom
%J Open Access Library Journal
%V 13
%N 4
%P 1-25
%@ 2333-9721
%D 2026
%I Open Access Library
%R 10.4236/oalib.1114914
%X The canonical affinity-threshold model of thymic T-cell selection posits that thymocyte fate is determined by TCR-pMHC integrated affinity. However, this model fails to explain high thymocyte deletion rates, diverse TCR affinities in mature repertoires, and precise CD4/CD8 lineage commitment mechanisms. We propose a novel Differential TCR Signaling Model wherein the functional TCR signal is a relative comparison: TCR¦Â signal strength relative to a dynamic TCR¦Á-derived self-reference threshold (TCR = TCR¦Â/TCR¦Á). This requires functional partitioning of pMHC recognition: TCR¦Á (via VJ recombination) engages the N-terminal peptide half (Seg1) to establish a tunable self-reference, while TCR¦Â (via V(D)J recombination) targets the C-terminal half (Seg2) harboring antigenic information. Consequently, thymic selection expands to four distinct checkpoints aimed at achieving Equivalence of Self-Recognition (TCR¦Á ¡Ö TCR¦Â) on self-ligands, ensuring near-zero differential signaling and stringent central tolerance. TCR¦Á rearrangement becomes an active ¦Á-negative selection process, reducing TCR¦Á affinity to balance fixed TCR¦Â signals. The kinetics of achieving equivalence deterministically dictate lineage fate: strong initial TCR¦Â signals promote rapid balancing and CD4 commitment, while weaker signals require prolonged tuning and often coreceptor reversal (CD4 ¡ú CD8) for MHC I balance, leading to CD8 commitment. This model redefines T-cell development as active, quantitative self-recognition calibration, providing a unified explanation for thymic attrition, repertoire diversity, and lineage choice, and establishing a quantifiable 3:1 self-to-antigen recognition confidence ratio fundamental to immune discrimination.<br />
%K Differential TCR Signaling
%K Differential Affinity Threshold
%K Repertoire Diversity
%K Segregated Peptide Recognition
%K Four Checkpoints in Thymic Selection
%K Equivalence of Self-Recognition
%U http://www.oalib.com/paper/6887979