Whereas no information is yet available on SLC7A7 expression and function in lymphoid populations, the high expression and activity of SLC7A7 in normal macrophages and the substantial defect in system y+L activity observed in LPI macrophages support the hypothesis of a pathogenetic role of these cells in the development of LPI-associated immunological disorders. The gene discussed is SLC7A7; the disease is lysinuric protein intolerance.