Ly-6 Superfamily Members Ly-6A/E, Ly-6C, and Ly-6I Recognize Two Potential Ligands Expressed by B Lymphocytes

Abstract

Most hemopoietic cells express one or more members of the Ly-6 supergene family of small glycosylphosphatidylinositol-linked proteins. Although levels of Ly-6 proteins vary with stages of differentiation and activation, their function largely remains unknown. To ascertain whether ligands for Ly-6 proteins exist, chimeric proteins were constructed in which Ly-6E, Ly-6C, and Ly-6I were fused to the murine IgM heavy chain. These chimeras specifically stained both developing and mature B lymphocytes, as assessed by flow cytometry. Analysis of variants of the CH27 B cell lymphoma revealed that Ly-6A/E and Ly-6I recognized different molecules. CH27 cells with low levels of Ly-6A/E ligand activity also lost expression of CD22, and cells transfected with CD22 gained the ability to bind the Ly-6A/E chimera and, to a lesser extent, the Ly-6C and Ly-6I chimeric proteins. As many mature B cells coexpress Ly-6A/E and CD22, the function of Ly-6 molecules may be to associate with other membrane proteins, possibly concentrating these ligands in lipid rafts, rather than acting directly as cell:cell adhesion molecules.

Intestinal Epithelial Cell Up-Regulation of LY6 Molecules during Colitis Results in Enhanced Chemokine Secretion

“…Ligands for LY6 molecules, including LY6A, have been described on the lymphoid cells; however, the identification of such ligands is controversial (52)(53)(54)(55). Furthermore, ligands have not been wholly identified.…”

Ly-6Chi monocytes dominate hypercholesterolemia-associated monocytosis and give rise to macrophages in atheromata

“…Following the fate of adoptively transferred, purified monocyte subsets revealed that lesional macrophages derived predominantly from circulating Ly-6C hi monocytes, pointing to an active role in this process for the membrane-bound, glycosylphosphatidylinositol-linked protein Ly-6C (44)(45)(46). Future studies will show whether Ly-6C serves only as a marker for or also contributes functionally to inflammatory monocytes, whether Ly-6C characterizes inflammatory cells capable of tissue transmigration, and whether therapeutic targeting of Ly-6C, or a human equivalent, contains monocytosis and consequently reduces atherosclerosis.…”

Fat-associated lymphoid cluster in Cyprinus carpio: Characterisation and its relation with peritoneal haemangiosarcoma

“…Sca-1 induces lymphocyte proliferation [32]; in the case of C. carpio, FALC cells probably act as engagers, leading to the fusion of this biomolecule with the IgM heavy chain of this fish species, as documented in mammals B lymphocytes [52]. In addition, Sca-1 causes the co-regulation of a variety of different signalling pathways that are able to modify the signalling capacity of the receptor complex [32]; in the case of C. carpio, FALC cells favour a Th2-type response.…”