Studies on the lymphocytes of sheep. II. Some properties of cells in various compartments of the recirculating lymphocyte pool.

The proportion of cells bearing surface immunoglobulin (Ig) and the normal lymphocyte transfer (NLT) reactivity of mononuclear cells obtained from the blood, afferent lymph, and efferent lymph from both somatic and intestinal nodes of sheep were measured. The proportion of Ig-positive lymphocytes was approximately 30% in blood and efferent lymph, but only about 10% in afferent lymph. The proportion of unlabeled lymphocytes (T cells) was about the same in all the preparations, as afferent lymph contains 15--20% macrophages. Despite this apparent uniformity in the T cell content, the NLT reactivity of efferent lymph was 3 to 5 times higher than that of blood or afferent lymph. No humoral factors could be detected by incubating cells in the various plasmas in vitro before injection. No inhibitory cells could be detected when mixtures of cell populations were used to initiate lesions. We suggest that lymphocytes in efferent lymph are more reactive than others because they are "groomed" by macrophages during their recirculatory passage through the substance of the node.