Subset-Specific Regulation of the Lymphatic Exit of Recirculating Lymphocytes In Vivo

Abstract

The blood-to-lymph recirculation of lymphocytes is required for the maintenance of immune surveillance and the dissemination of memory. Although the ability of lymph-borne cells to recirculate has been well documented, relatively less is known about the migration capacity of PBLs. We have found a clear preference for PBLs to recirculate through s.c. rather than intestinal lymph nodes. This preference could be directly attributed to the migratory characteristics of γδ-T cells. γδ-T cells were found to express significantly higher levels of L-selectin than other subsets, suggesting that at least some of this preferential migration could be attributed to their interaction with ligands on vascular endothelium. More detailed experiments showed that γδ-T cells migrated through lymph nodes with greater efficiency than αβ T cells or B cells, which clearly indicated an enhanced ability of γδ-T cells to exit lymph nodes in the efferent lymph independent of entry from the blood. This hypothesis was supported by histological examination, where γδ-T cells were found almost exclusively in the interfollicular traffic areas within lymph nodes. These data indicate that γδ-T cells are the most active recirculating lymphocyte subset in ruminants and suggest new mechanisms to regulate the traffic of lymphocyte subsets through normal lymph nodes.

γδ T Cell Homing to Skin and Migration to Skin-Draining Lymph Nodes Is CCR7 Independent

“…Considering the average lymph flow of 20 ml/h (4), the 2-fold enrichment of gd T cells in the afferent and efferent lymph implies that there is substantial egress of gd T cells from the skin trafficking into the draining lymphatic system ultimately draining into the venous circulation. The relatively low proportion of gd T cells found in the LN under homeostatic conditions has been described earlier in sheep (19) and contributes to the idea that gd T cells travel through the lymphatic system with minimal interaction in the LN.…”

“…6B (25). High CD62L expression is a known feature of ruminant gd T cells and probably contributes to their highly mobile profile, as suggested by previous studies (19,26).…”

“…Labeling of lymph cells was performed as described earlier (19). After labeling, the cells were injected back into the bloodstream of the donor calves via the jugular vein.…”

Characterisation of the lymph node immune response followingMycoplasma mycoidessubsp.MycoidesSC infection in cattle

“…Significant γδ T-cell activation was observed in the MmmSC-specific peripheral immune response [5] while it could not be detected in this study. Indeed, while γδ T-cells are a significant component of the afferent and efferent lymph and, in ruminants, may constitute up to 50% of the PBMC in young animals, they are only a minor population within the lymph nodes, suggesting that they re-circulate preferentially through non lymphoid tissues [33].…”

Lymphocyte migration studies

“…After in vitro labelling this cell subset preferentially remigrates into the intestinal wall [93]. Experiments in sheep have also demonstrated the quick recirculation of γ/δ T cells [103,104]. However, lymphocyte migration studies in the mucosal immune system in large animals so far have not contributed to the understanding of the regulation of antigen specific cell migration.…”