T-cell receptor-peptide-MHC II complex (TCR-pMHC II) (TCR-pMHC II)

The T-cell receptor (TCR) recognition of tuberculin purified protein derivative (PPD)-derived peptide–MHC II complexes is a fundamental immunological interaction essential for the detection and control of Mycobacterium tuberculosis infections [PMID: 23913962]. This process involves the specific binding of a TCR on a sensitized CD4+ memory T cell to a mycobacterial peptide fragment presented by Major Histocompatibility Complex class II (MHC II) molecules on the surface of antigen-presenting cells [PMID: 22461495]. This molecular recognition event triggers a robust secondary immune response, characterized by the activation of signaling pathways that lead to T-cell proliferation and the secretion of pro-inflammatory cytokines, particularly interferon-gamma (IFN-γ) [PMID: 28931618]. Clinically, this interaction is the biological basis for the Tuberculin Skin Test (TST) and Interferon-Gamma Release Assays (IGRAs), which are the gold standards for diagnosing latent tuberculosis [StatPearls: NBK442028]. While not a target for conventional small-molecule inhibitors, this complex is the primary focus of vaccine development, such as the Bacillus Calmette-Guérin (BCG) vaccine, and novel immunotherapeutic strategies designed to modulate cellular immunity [PMID: 31209119]. Therapeutic challenges include the risk of severe delayed-type hypersensitivity reactions, known as the Koch phenomenon, and the potential for cross-reactivity with non-tuberculous mycobacteria or prior BCG vaccination, which can complicate diagnostic interpretation [PMID: 25631447].

Other names

PPD-specific T-cell receptorTCR-antigen-MHC complexCD4+ T-cell receptor complexMHC class II-peptide complex

Activation of memory CD4+ T cells through TCR binding to mycobacterial peptide-MHC II complexes, inducing a Th1 cytokine response and delayed-type hypersensitivity.