SYK and IgA glomerulonephritis: Historical data have suggested that glomerular and tubulointerstitial mononuclear phagocytic cell infiltration is associated with a worse prognosis in IgA nephropathy54; that CD89 expression on circulating leukocytes is up-regulated in IgA nephropathy patients, independent of plasma IgA levels, and that CD89 expression in glomeruli also may be increased compared with normal controls and patients with other forms of proliferative glomerulonephritis.55, 56 CD89 associates with FcRγ chain, an ITAM-containing adaptor protein, and multimerization of the receptor has been shown to activate SYK.57