Which percentage of labeled T cells should I find in the peripheral lymph nodes after adoptive transfer of say 5-10 million labeled T cells? Is there a difference in efficiency between the intraperitoneal and intravenous routes? I find intraperitoneal injections to be very reproducible and reliable, whereas tail-vein injections can be quite variable from mouse to mouse. We just transferred 35 million CFSE-labeled CD3+ cells by intraperitoneal injection to 12 mice and we observed between 0.4-0.7% labeled cells in the popliteal and cervical lymph nodes 48 h later. I was expecting to find about 10 times that number...