Receptor for transcobalamin saturated with cobalamin (TCbl) (PubMed:18779389). Plays an important role in cobalamin uptake (PubMed:18779389, PubMed:20524213). Plasma membrane protein that is expressed on follicular dendritic cells (FDC) and mediates interaction with germinal center B cells (PubMed:10727470). Functions as costimulator to promote B cell responses to antigenic stimuli; promotes B cell differentiation and proliferation (PubMed:10727470, PubMed:11418631). Germinal center-B (GC-B) cells differentiate into memory B-cells and plasma cells (PC) through interaction with T-cells and follicular dendritic cells (FDC) (PubMed:11418631). CD320 augments the proliferation of PC precursors generated by IL-10 (PubMed:11418631). Interacts (via LDL-receptor class A domains) with TCN2 (PubMed:27411955). Detected in the germinal center (GC) of lymphoid follicles (at protein level) (PubMed:11418631). Expressed abundantly on follicular dendritic cells (FDCs) (PubMed:10727470). The disease may be caused by variants affecting the gene represented in this entry.