T lymphocytes are the first responders that then coordinate the immune response. Testing T cell responses can accelerate detection of an infection by as much as a week. The cells come in on day 2 and they divide very quickly, to detectable levels as early as 3 or 4 days from infection as per Dawn Jelley-Gibbs from New York.
T cells descend from stem cells in the bone marrow. During development, they migrate to the thymus gland (“T”), where they display antigens that are whittled down to those that recognize self. Antigens distinguish subtypes: CD4 T cells (“helpers”) recognize foreign antigens on macrophages, stimulate B cells to produce antibodies, secrete cytokines, and activate CD8 T cells (“cytotoxic”). CD8 T cells burst virally-infected cells.
T cell receptors (TCRs) are astonishingly diverse. Researchers have assessed TCR diversity using binding to varied quartets (“tetramers”) of the MHC peptides that macrophages display.
Researchers from the University of Freiburg in Germany tracked CD8 T cells in 26 convalescing patients for 100 days and reported their findings in Nature Medicine. They did not observe a substantial decline during the follow-up. Alba Grifoni, PhD, and colleagues pointed out in Cell on June 25 that identifying T cell responses can provide insights into the pathogenesis and rise of immunity, inform vaccine development, and refine public health measures.
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