From Moore (2014)

There is evidence that cytotoxic T cells participate in controlliing tumor
growth and that they can be harnessed to use the body's immune system to treat
cancer.  ne study investigated the use of a T cell-engaging antibody,
blinatumomab, to recruit T cells to control tumor growth.  THe data in
tcells.dat are T cell counts (in 1000s per microliter) at baseline
(the beginning of the study) and after 20 days on blinatumomab for 6
subects in the study.  The difference (after 20 days minus baseline) is the
response variable.

THe variables are:
      baseline
      day20