[The differential diagnostic significance of the binding capacity of serum immunoglobulins with amino acids in rheumatism, rheumatoid arthritis and systemic lupus erythematosus with a minimal degree of activity].

The ability of immunoglobulins (Ig) G, A and M to bind to amino acids was studied in 27 patients with rheumatism (R), 28 with rheumatoid arthritis (RA) and 27 patients with systemic lupus erythematosus (SLE) with minimum degree of activity. The enhancement of the binding capacity of IgG with respect to arginine, glutamic acid, lysine and decrease of that of IgM towards serine was established to be of diagnostic value in R as was the enhancement of the above capacity of IgG and A with respect to proline and oxyproline in RA and enhancement of that of Ig of all three classes with respect to a broad range of amino acids in SLE. Information criteria were established of differential diagnosis of R, RA and SLE.