Tlymfosyyttien

Tlymfosyyttien, commonly known in English as T lymphocytes or T cells, are a diverse group of lymphocytes that mediate adaptive immunity. They originate from hematopoietic stem cells in the bone marrow and mature in the thymus, where they undergo selection to ensure proper MHC restriction and self-tolerance. Mature Tlymfosyyttien express the T-cell receptor (TCR) complex with CD3 and participate in antigen recognition presented by major histocompatibility complex (MHC) molecules on antigen-presenting cells.

Functionally, Tlymfosyyttien are divided into several major subsets. Helper T cells (CD4+) coordinate immune responses by signaling other immune cells through cytokines. Cytotoxic T cells (CD8+) destroy infected or abnormal cells via cytolytic mechanisms. Regulatory T cells suppress excessive or misguided immune responses to maintain tolerance. Memory T cells persist after an infection to enable faster responses upon re-exposure.

Activation requires two signals: TCR engagement with peptide-MHC and a co-stimulatory signal such as CD28-B7. Once activated, clonal expansion produces effector T cells and, over time, memory cells. Tlymfosyyttien patrol tissues and circulate in blood and lymph, encountering pathogens, presenting cells, and transformed or infected cells. Their activity is coordinated with other immune components, including B lymphocytes and innate immune cells.

Clinical relevance: T lymphocyte function is central to immunodeficiency, autoimmunity, and transplantation biology. Immunotherapies, including checkpoint inhibitors and engineered T cells (CAR-T), exploit Tlymfosyyttien capabilities to target cancer and chronic infections. The study of Tlymfosyyttien remains active, with ongoing research into thymic selection, differentiation pathways, and tissue-resident memory formation.