The transferrin receptor (CD71) perhaps is the best characterized of these, being expressed on human mesangial cells, and up-regulated and co-localized with IgA1 deposits in IgA nephropathy.46, 47 Cross-linkage of CD71 by IgA can induce mesangial cell proliferation and cytokine production.48 Here, IGHA1 is linked to IgA glomerulonephritis.