Analysis of lymph flow velocity and physiology. (A) Quantitative analysis using residence time distribution theory reveals a significant difference in the lymph flow velocity of fluorescent dextran in tail lymphatics between LTα^−/− and wild type (WT) mice, but not between LTβ^−/− and WT mice (a minimum of n = 10 mice per group; *P < .05). (B) Extracellular fluid volume (EFV) in paw skin measured during steady state control situation () and after overhydration (). In contrast to LTα^−/− mice (n = 8 in control [c] and overhydration [o]), both LTβ^−/− (n = 8 [c] and n = 9 [o]) and WT (n = 6 [c] and n = 4 [o]) mice show a significant increase in EFV after overhydration (*P < .05). (C) LTα^−/− mice (n = 16) have a significantly higher interstitial fluid pressure (Pif) than both LTβ^−/− (n = 17) and WT mice (n = 10) during steady state control situation (*P < .05). All 3 groups, however, demonstrate a significant increase in Pif after overhydration (#P < .05). (D) Colloid osmotic pressure (COP) in plasma and interstitial fluid in the steady state control situation. LTα^−/− mice show comparable COP in the interstitial fluid to WT and LTβ^−/− mice. (E) After overhydration, the LTα^−/− mice (n = 6) show a significantly higher COP in the interstitial fluid in comparison to WT mice (n = 7; *P < .05). (F) Colloid osmotic pressure gradient (ΔCOP) across the capillaries in the steady state control situation and after overhydration. All 3 groups show a nonsignificant decrease in ΔCOP after overhydration. Overhydrated LTα^−/− (n = 6) mice have a significantly lower ΔCOP compared with WT (n = 7) mice (*P < .05).