What diseases cause elevated serum polyclonal FLC concentrations?
Serum polyclonal FLC concentrations increase if there is increased production orreduced glomerular filtration of κand λproteins. Increased production results from anydisease that stimulates B-cell proliferation such as infections, autoimmune diseases,various tumours etc. For example, in active SLE, total immunoglobulin productionincreases 3-4 fold with a corresponding increase in sFLC concentrations. Reduced glomerular filtration of FLCs occurs in renal damage because almost allFLC removal is via the glomerular pores and the proximal renal tubules. In renal failure,sFLC concentrations may rise 10-20 fold but in all cases both free κand λare elevated,so the free κ/λratio remains normal. In many diseases, particularly SLE, increases inpolyclonal FLC concentrations are due to a combination of increased FLC productionand reduced renal filtration. In situations of increased polyclonal FLC production or reduced filtration, there maybe moderate distortions of κ/λratios (e.g., 3-4 standard dev
