Normal human serum also contains the lymphotoxin found in minimal change nephropathy

We have studied serum-borne lymphotoxic activity in a large patient group with various forms of glomerulonephritis (GN). A potent inhibitor of lymphocyte blastogenesis was frequently demonstrable not only in patients with active minimal change nephropathy as has been previously described, but also in other forms of GN. The inhibitor was resistant to heating and prolonged storage but rendered ineffective by normal serum. We have been able to show for the first time, using gel filtration, that normal serum also contains the inhibitor. The inhibitor was shown to be highly avid for a receptor on leucocytes as judged by dose response experiments and by the ability of cell pellets to remove this activity. Gel filtration demonstrated a molecular weight in the range 60 to 160 kilodaltons. The combination of information regarding the biological properties of the inhibitor, its clinical occurrence and molecular weight suggests it to be distinct from any other well-described lymphotoxin. It's presence in normal serum in association with a self-regulatory factor and the known proclivity of minimal change nephropathy patients to infection, also indicate that the inhibitor may play an important role in immunoregulation.