Towards a comprehensive human cell-surface immunome database

The human immune system is a complex machinery involving numerous proteins. Proteins located at the cell surface of immune cells are of particular relevance due not only to their participation in the network of interactions that regulate the immune response but also to their potential as excellent targets for diagnostic and therapeutic interventions. The main objective of this project is to generate a comprehensive database of the human cell-surface proteins expressed in immune cells and lymphoid tissues. For this purpose, we have integrated information collected from primary literature, databases and electronic information sources. This manually curated database includes the gene symbol and name of the protein, describes the family that each protein belongs to, indicates their type of extracellular domains, and compiles data regarding their expression. Thus far we have identified and catalogued 1015 genes and proteins. The largest families in this compendium are the Ig superfamily with 195 members (~20%) and the G-protein coupled receptor superfamily with 147 members (~14%). Other abundant families include the C-type lectin and the cytokine receptor families with 43 and 42 members respectively (4%). About 25% of the proteins belong to minor families and approximately 4% lack any clear family assignment. More than 60% of the genes encode proteins without a CD number. This database will serve to boost the production of new monoclonal antibodies and to stimulate studies aimed at characterizing the function of these proteins in the immune system as well as identifying potential new biomarkers and therapeutic targets.