Pathophysiological aspects of lymphedema of human limbs: I. Lymph protein composition

The knowledge of humoral and cellular factors retained in tissues affected by ineffective lymph transport is necessary to comprehend the pathological mechanisms of the evolving changes in the extremity. In this article, we report our observations on changes in the protein composition of lymph in obstructive lymphedema. We have documented that the protein concentrations in lymph tissue fluid of the extremities remain within normal limits in lymphedema of stages I through III. Normal lymph protein values in lymphedema indicate that the homeostatic mechanism of protein transport remains intact as long as there are no major structural changes in the tissues that imply loss of tissue space compliance. A "high protein" edema means "high protein volume" edema that does not affect the Starling's equilibrium. The levels of cytokines were found to be elevated in lymphedema lymph when compared with controls. There were major differences in cytokine levels among patients, evidently higher than those among the control subjects. The high levels of cytokines might be attributed to their local production by infiltrating immune cells. The serum levels remain low, and the lymph-to-serum ratio was above 1 in all the cases investigated. These findings reflect the intensity of the chronic inflammation that prevails in tissues with lymph stasis, not detectable by measuring the levels of lymph immunoglobulins and complement. Moreover, our studies have documented the presence of apoptotic DNA in the lymph of patients with obstructive lymphedema. There were greater quantities of 400-kb apoptotic and smaller DNA fragments in the lymph from lymphedematous limbs than in the controls. The level of fragmented DNA may be another parameter that reflects cellular changes in tissues with lymph stasis. Taken together, measuring levels of lymph proteins provides insight into the evolving processes in the limb tissues.