T cell

A lymphocyte that matures in the thymus and recognizes antigen fragments displayed by other cells. T cells coordinate immune responses or directly kill infected and abnormal cells.

T-cell receptor: A receptor complex on T cells that recognizes specific antigen fragments bound to major histocompatibility complex molecules. Its antigen recognition starts the chain of events that activates a T cell.
Thymus: A lymphoid organ where developing T cells mature and undergo selection. T cells acquire functional receptors and pass selection in this organ.
CAR T-cell therapy: A cancer treatment that engineers a patient’s T cells to recognize selected targets through synthetic receptors. It redesigns T-cell recognition to attack certain cancers.
B cell: A lymphocyte that can mature into an antibody-secreting plasma cell and can present antigen to helper T cells. B cells recognize intact antigens and produce antibodies, unlike T cells’ usual recognition of presented fragments.
HIV: A virus that infects immune cells, especially CD4-positive T cells, and can cause acquired immunodeficiency syndrome. Its loss of helper T cells weakens coordination across the immune system.
Major histocompatibility complex: A group of cell-surface proteins that display peptide fragments for recognition by T cells. T cells usually recognize antigens only when these molecules present them.
Antigen: A molecule or molecular structure that can be specifically recognized by an immune receptor or antibody. T-cell receptors respond to antigen-derived fragments, not usually intact antigens.
Immune checkpoint blockade: Cancer treatment that inhibits immune-regulating proteins to strengthen antitumor immune activity. It can release inhibitory signals that restrain tumor-reactive T cells.
Natural killer cell: An innate lymphocyte that kills some abnormal cells without a rearranged, antigen-specific receptor. It can kill targets without the antigen-specific recognition required by conventional T cells.
Autoimmunity: An immune response directed against the body’s own molecules, cells, or tissues. Self-reactive T cells can help initiate or sustain attacks on the body’s tissues.

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