Serial leukocyte (WBC) counts in MSCV-FL mice. Each line represents data from a single animal: mice 196, 197, 199, 203, 204, 208, and 209 are primary recipients; mice 198.2, 201.1, 205.2, 210.1, 210.2, 211.1, 211.2, 230.2, and 231.1 are secondary recipients.