Low molecular weight (7S) IgM and free light chains in the sera of patients with the tropical splenomegaly syndrome.

The presence of naturally occurring LMW (7S) IgM was suspected on Sephadex G-200 filtration of a serum pool from patients with tropical splenomegaly syndrome (TSS). It was found in nineteen out of thirty-one sera from these patients using a polyacrylamide/agarose gel-diffusion method, and in fifteen of the sera after precipitation of the 19S IgM with 10% polyethylene glycol (PEG). Free K-light chains was detected in twenty-five out of thirty-one sera from patients with the TSS while free lambda-light chains was detected in four. The presence of 7S IgM and free light chains in sera of these patients is in keeping with our hypothesis that there is a disorder of control of immunoglobulin production in the tropical splenomegaly syndrome.