Tracking Antigen-Specific Lymphocytes In Vivo

With the development of antigen-specific T-cell-receptor (TcR) and B-cell-receptor (BcR) transgenic (Tg) mice, it is now feasible to track single, antigen-specific lymphocyte populations throughout the course of an immune response. Adoptive transfer of the transgenic cell populations into na�ve recipients with the same genetic background increases precursor frequency sufficiently to allow researchers to locate and functionally assess lymphocytes, in the physiological context of a normal animal, early after antigen exposure (1 –4 ). Prior to the availability of such transgenic mice, it was extremely difficult to track lymphocytes in vivo during the early phases of an immune response before significant clonal expansion, because of the low precursor frequency of antigen-specific B- and T-cells. The following methods will illustrate some of the techniques now available for the tracking of antigen specific B- and T-cell populations in vivo.