The L-selectin counter-receptor in porcine lymph nodes

Membrane markers of the immune cells in swine: an update

Besides their breeding value, swine are increasingly used as biomedical models. As reported in three international swine clusters of differentiation (CD) workshops and in the animal homologue section of the last workshop for the determination of human leukocyte differentiation antigens (HLDA 8), characterisation of leukocyte surface antigens by monoclonal antibodies and other molecular studies have determined the cell lineages and blood leukocyte subsets implicated in the immune response, including cell adhesion molecules involved in cell trafficking. This review focusses on the current state of knowledge of porcine leukocyte differentiation and major histocompatibility complex (SLA) molecules. Examples of porcine particularities such as the double-positive T lymphocytes with the phenotype CD(4+)CD8(low) and CD(4-)CD8(low) alphabeta T cell subsets and the persistence of SLA class II after T-lymphocyte activation are illustrated, as well as the shared characteristics of the Artiodactyla group, such as the high proportion of gammadelta TcR (T cell receptor) T cells in blood and other lymphoid tissues. Furthermore, discrepancies between swine and humans, such as CD16 expression on dendritic cells and CD11b (wCD11R1) tissue distribution are outlined. The rapidly growing information should facilitate manipulation of the swine immune system towards improving disease control, and open new avenues for biomedical research using the pig as a model.

Identification and characterization of L-selectin ligands in porcine lymphoid tissues

A human L-selectin-ZZ fusion protein was used to screen porcine inguinal lymph nodes for the presence of monoclonal antibody (mAb) MECA 79-negative ligands. Fractionation of lymph node-conditioned medium by anion-exchange chromatography revealed two distinct L-selectin-binding fractions, one containing a MECA 79 non-reactive species and the second containing two MECA 79 reactive species of approximately 84 000 and 210 000 molecular weight. The MECA 79 non-reactive species exhibited Ca2+- and lectin-dependent binding to L-selectin-ZZ in a solid-phase capture enzyme-linked immunosorbent assay (ELISA), and this was specifically disrupted by the addition of EDTA, mannose-6-phosphate and the blocking anti-L-selectin mAb, DREG-56. Enzymatic characterization of the ligand by trypsin, O-sialoglycoprotease endopeptidase, heparinases I and III, or chondroitinase ABC lyase digestion indicated that L-selectin binding was predominantly dependent upon a chondroitin sulphate-modified glycoprotein determinant. Although Coomassie Blue staining of sodium dodecyl sulphate (SDS) polyacrylamide gels did not reveal a detectable protein species, carbohydrate-specific staining using GlycoTrack revealed a single, heavily glycosylated protein of high molecular weight (> 220 000). These studies have revealed the existence of a MECA 79 non-reactive, chondroitin sulphate glycosaminoglycan-modified ligand, termed csgp>220, which is secreted by peripheral lymph nodes and may play a role in leucocyte trafficking to the lymph node.