B and T cells are important in vaccines, infections, autoimmunity, aging, and cancer. There are millions of these cells in a typical blood sample. High-throughput sequencing and big-data computational biology make it possible to investigate how this unique set of cells carries out its functions—and raise the possibility of using them as early diagnostics and biological therapeutics for a range of conditions. In our lab, we are sequencing and analyzing antibodies and T cell receptors across species and medical conditions to understand this complex system. Specific projects include sequencing and analysis of B- and T-cell repertoires in melanoma and cancer and other vaccines.