Immunoregulatory Semaphorin Receptor CD72 Atsushi Kumanogoh and Hitoshi Kikutani* Department of Molecular Immunology, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan * corresponding author tel: +81-6-6879-8363, fax: +81-6-6875-4465, e-mail:
[email protected] DOI: 10.1006/rwcy.2002.1421.
SUMMARY CD72, which was initially identified as mouse Lyb-2 surface protein, is a type II transmembrane glycoprotein belonging to the C-type lectin family. Although crosslinking of CD72 by monoclonal antibodies (mAbs) enhances B cell activation, CD72 has immunoreceptor tyrosine-based inhibitory motifs (ITIMs), suggesting that it functions as a negative regulator of B cell responses. CD100 binds to CD72 and enhances B cell responses by turning off negative signals of CD72.
BACKGROUND
Discovery CD72 was originally identified as Lyb-2 cell surface glycoprotein with its expression restricted to B lineage cells (Sato and Boyse, 1976; Yakura et al., 1981). Conventional antisera and monoclonal antibodies (mAb) identified three allotypes of Lyb-2 antigen, Lyb-2.1, Lyb-2.2, and Lyb-2.3. Molecular cloning revealed that Lyb-2 is a 45 kDa type II transmembrane protein that belongs to the C-type lectin family (Nakayama et al., 1989; Von Hoegen et al., 1990). CD72 is expressed throughout B cell differentiation from the earliest B cell progenitors to mature B cells,
Cytokine Reference
but the expression is downregulated upon terminal differentiation into plasma cells (Nakayama et al., 1989; Von Hoegen et al., 1990; Tutt Landolfi and Parnes, 1997).
Alternative names Lyb-2, Ly-19.2, Ly-32.2 (mouse)
Structure CD72 is a type II transmembrane glycoprotein expre