Lymphocyte traffic through chronic inflammatory lesions: differential migration versus differential retention.

Afferent lymphatics draining granulomas and efferent lymphatics from normal lymph nodes were cannulated in sheep. Cells collected from these lymphatics were radiolabelled in vitro with 111In (afferent lymph cells) and 51Cr (efferent lymphocytes) and both labelled cells were returned to the animal simultaneously by i.v. injection. The reappearance of these labelled cells in lymph, and the amount of 111In and 51Cr in normal or antigenically stimulated lymph nodes, cutaneous inflammatory sites (FCA-granulomas, NLT- and BCG-induced lesions) and blood was determined 24 hr later. As previously reported, labelled afferent cells preferentially migrated from the blood back through the granuloma into afferent lymph, and efferent lymphocytes back into efferent lymph. Forty per cent as many 111In- as 51Cr-labelled cells ;appeared in efferent lymph. This was caused by the greater migration of 51Cr-labelled cells appeared in efferent lymph. This was caused by the greater migration of 51Cr- than 111In-labelled cells out of the blood into the node. Neither cell type was selectively retained in the node, and 28% of the labelled cells that entered the node migrated on into efferent lymph in 24 hr. Similarly, there was no selective retention of either cell type in the granuloma, and equal amounts of 111In the 51Cr appeared in afferent lymph. The ratio 111In/51Cr in the blood suggested that in the lymph node the two labelled cell populations were extracted equally, while in the granuloma selectively at the level of the vascular endothelium resulted in the preferential extraction of 111In-labelled (afferent lymph) cells.