Figure 1. Structure of the human T-cell receptor. Courtesy of D. Garboczi.

Figure 2. Biosynthesis of nonpeptide phosphoantigens recognized by human T lymphocytes. Left, microbial pathogens, e.g. Mycobacterium tuberculosis, the agent of human TB produces the HDMAPP phosphoantigen to make cholesterol; right, in human cells, cholesterol biosynthesis proceeds by the mevalonate pathway and produces IPP and DMAPP phosphoantigens.

Figure 3. Stimulation of a human T lymphocyte by the MHC-unrestricted recognition of a small nonpeptidic antigen. Its TCR-mediated activation threshold is balanced by inhibitory signals triggered by the interaction of INMR with MHC class I on target cells. Zap, -associated protein of 70 KDa.

Figure 4. A human T lymphocyte rapidly scans the surface of an anaplastic lymphoma cell target (green cytoplasm and blue membranes) for stimulating and inhibitory signals. Once fully activated, the T lymphocyte kills this target by secreting its cytolytic perforin granules (stained red). The green fluorochrome (calcein AM) is a viability cytoplasmic stain, whose loss indicates cell death. For easier views, the target cell membrane was labelled with a blue fluorochrome.