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). CD320 augments the proliferation of PC precursors generated by IL-10. Receptor for the cellular uptake of transcobalamin bound cobalamin.

Expressed abundantly on follicular dendritic cells (FDCs).

Defects in CD320 are the cause of methylmalonic aciduria type TCblR (MMATC) [MIM:613646]; also called methylmalonic aciduria due to transcobalamin receptor defect. MMATC is a metabolic disorder characterized by increased blood C3-acylcarnitine levels, elevated methylmalonate and homocysteine, and low uptake of transcobalamin-bound cobalamin, but normal conversion to adenosylcobalamin and methylcobalamin. Plasma vitamin B12 and total homocysteine are normal.

Contains 2 LDL-receptor class A domains.

Membrane.