W. Michael Gallatin

A cell-surface molecule involved in organ-specific homing of lymphocytes

Lymphocytes migrate from the bloodstream by recognizing and binding to specialized endothelial cells lining the high endothelial venules (HEV) in lymph nodes and Peyers patches. We describe here a monoclonal antibody, MEL-14, specific for a lymphocyte surface molecule that appears to mediate recognition of lymph node HEV, and to be required for lymphocyte homing into lymph nodes in vivo.

A homing receptor-bearing cortical thymocyte subset: Implications for thymus cell migration and the nature of cortisone-resistant thymocytes

The thymus exports a selected subset of virgin T lymphocytes to the peripheral lymphoid organs. The mature phenotype of these thymus emigrants is similar to that of medullary thymocytes and has been cited as supporting a medullary rather than cortical exit site. Using the monoclonal antibody MEL-14, we identify a 1%-3% subpopulation of thymocytes that expresses high levels of a receptor molecule involved in lymphocyte homing to peripheral lymph nodes. We present evidence that these rare MEL-14hi thymocytes are predominantly of mature phenotype and represent the major source of thymus emigrants. Surprisingly, MEL-14hi thymocytes are exclusively cortical in location, although their mature phenotype may allow them to masquerade as medullary cells in conventional studies. We also demonstrate that unlike medullary thymocytes, many cortisone-resistant thymocytes (CRT) are MEL-14hi. Thus, in contrast to current dogma, CRT do not represent a sample of medullary thymocytes as they are found in situ and their level of immunocompetence does not necessarily reflect that of the medullary population. Our findings refute the hypothesis that phenotypically and functionally mature cells are restricted to the medulla, and support our proposition that most thymus emigrants are derived from the MEL-14hi cortical subset.

Isolation of molecules recognized by monoclonal antibodies and antisera: the solid phase immunoisolation technique

A simple technique for the isolation of antigens recognized by antisera and monoclonal antibodies has been developed. This method, the solid-phase immunoisolation technique, employs the protein-binding properties of polyvinylchloride microtiter plates. Antibodies are adsorbed to the plates either directly or via an anti-immunoglobulin reagent. Antigen is then placed in the wells, and allowed to adsorb to the antibody. The well is washed, and the antigen is then eluted with a denaturing electrophoresis sample buffer for one- or two-dimensional analysis. The solid-phase immunoisolation technique has been used to isolate a variety of cell membrane antigens with high signals and low backgrounds. The ease of the procedure and the high signal-to-noise ratio make this method preferable to the use of a staphylococcal adsorbent for many applications.

Changes in Topography of Cell Adhesion Molecules during Lymphocyte Migration Across Endothelium

The widely expressed CD44 single-chain transmembrane glycoprotein has been the object of recent studies in the fields of cell adhesion and lymphocyte activation. This molecule commonly occurs as a 37-kDa polypeptide extensively glycosylated with N- and O-linked oligosaccharides and glycosaminoglycans which migrates in SDS-PAGE as an 80–95-kDa major component of the membranes of most cell types examined (1–3). Higher-molecular-weight forms bearing chondroitin sulfate have been described in lymphoid cells. In other cell types alternately spliced iso-forms possessing an additional extracellular domain exon of 132 or 162 amino acids have been detected (4,5).