Table 1 Important Issues in the Design of Experiments Studying the Migration of T Cells In Vivo

Source

Use T cells from blood and lymph because these cells are the only population usually available for migrating into organs.

Label

Control for toxicity by determining recovery (more than 80% of the injected cells), lymph node entry, and liver localization (less than 20% of the injected cells).

Site of injection

Intravenous injection facilitates accurate quantification of the cells available for immigration.

Recipient

Use genetically unmanipulated animals, and investigate 6 to 8 animals per time point to account for the variability of in vivo migration experiments.

Analysis

Study several organs and time points, and determine background levels.

Interpretation

Relate the number of T cells found in the animal to the number of injected T cells, and be aware that T cells, in contrast to granulocytes, not only enter but also exit a given tissue, and not only die but also proliferate within a given tissue. Thus, the number of T cells within a tissue depends on many factors.