Determination of the sensitivity of the TCR V_β spectratyping technique. Detection of spectratyping sensitivity was performed on the basis of flow cytometry, and the sorted positive cells were mixed with negative cells to produce fixed proportions of the specific V_β's in negative cell populations (0, 10, 10²,10³,10⁴, and 10⁵ V_β⁺ cells in 10⁶ cell population for each V_β subfamily). Total RNA (aapproximately 1 μg) was extracted from cells (10⁶), and standard spectratyping performed. The experiments were repeated 3 times. The lowest cell number detectable in 10⁶ mixed population is 100 to 1000 cells for random selection of V_β2, V_β14, and V_β22.