TCR Vβ spectratyping in foamy virus–treated dogs. The TCR β chain was amplified from complementary DNA using 17 different primer pairs to measure variable region rearrangements. The normal dog (R2197) is a littermate control of R2202 and R2203. Numbers on the left denote the age of the animal at analysis, and the labels at the bottom indicate the forward primer used. d.o., days old; N.D., not detectable. *Sample at necropsy.