An immunoglobulin is composed of heavy chains and light chains, but the light chains also wander around by themselves, having an inflammatory effect. These are called free light chains.
The FLC’s can be specific to antigens and cause mast cells to degranulate, so they provide a non-IgE hypersensitivity mechanism.
Here’s an abstract of a dissertation
“Immunoglobulin free light chains in inflammatory diseases: New findings on FLCs fitted into current concepts of immune regulation”
According to this abstract, FLC's are also elevated in rheumatoid arthritis, breast cancer (sometimes), and are involved in tumor growth in melanoma. Yikes!
I wonder if FLC’s are elevated in the blood of people with delayed food allergies. By "delayed food allergy" I mean a food reaction characterized by a groggy (dazed, mentally impaired) state that starts coming on about 1/2 hr after eating the food and comes on fully 4-5 hrs after eating and lasts about 4 days; other symptoms may include physical clumsiness; diarrhea; itching; frequent urination; and psychological effects like irritability, emotional hyper-reactiveness, tension.
FLC’s are involved in sensitization to casein (a milk protein) in mice:
There’s even a FLC antagonist called F991, a 9-mer peptide.
Also, prebiotic oligosaccharides reduce the blood level of FLC’s and reduce symptoms of atopic dermatitis in infants:
A “prebiotic” encourages the growth of good bacteria in the gut.
Very interesting …