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- than ¹¹¹-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 and 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 selectivity at the level of the vascular endothelium resulted in the preferential extraction of ¹¹¹In-labelled (afferent lymph) cells.