[Pathogenetic significance of adenosine deaminase in autoimmune diseases]

Adenosine deaminase (ADA: E.C.3.5.4.4.) is one of the catabolic enzymes of purine nucleotide. In 1972 Gibllet has discovered two cases of ADA deficiency combined with severe immunodeficiency (ADA-. SCID) with remarkable dysfunction in both T and B cell. Thereafter, it has been believed by many investigators that deficiency of purine metabolic enzyme had played important role in immune function mechanism. Rheumatoid arthritis (RA) is one of the autoimmune diseases which is very frequently seen, but its pathogenesis is not distinct yet. This study has shown how the catabolic pathway of erythrocytes and lymphocytes in RA has been distorted.

Erythrocytes and lymphocytes in peripheral blood were obtained from patients with RA (48 cases), SLE (4), primary gout (55) and healthy control (23). 2. T cell and non-T cell in peripheral blood were obtained from patients with RA (5), gout (55) and healthy control (28). 3. T cell and non-T cell in joint fluid were obtained from patients with RA (19) and osteoarthritis (OA (9)).

Erythrocytes and lymphocytes were separated from peripheral blood by Ficoll-Conray (density 1,077) by use of gradient centrifugation method. The lymphocytes with PBS was mixed with sheep red blood cells. E rosette-positive (T cell) and E rosette-negative (non-T cell) populations were separated from lymphocytes in peripheral blood and joint fluid by human sodium metrizoate Ficoll mixed solution (density 1,090) by use of gradient centrifugation method. Erythrocytes bursted at -70 degrees C and lymphocytes were sonicated for 25 sec. at 20 kHz. The reaction mixture which consisted of 0.2 mM Tris-HCl buffer (pH 7.4), 30 mM [8-14C] adenosine and the samples was incubated at 37 degrees C for 30 min. After incubation, adenosine, inosine and the reaction mixture were applied on DEAE-cellulose paper. Radioactivity of the samples was measured with liquid scintillation counter.

There was no significant difference in ADA activity of erythrocytes between normal male and female, but a significant difference was found in ADA activity of lymphocytes among its subpopulations. ADA activity of erythrocytes and lymphocytes in RA patients was much lower than the other groups (gout and normal subjects). Particularly, ADA activity in T cell was the lowest. In gouty patients, ADA activity of erythrocytes and T cell was higher. ADA activity of peripheral erythrocytes in RA patients was lower than that of joint fluid.(ABSTRACT TRUNCATED AT 400 WORDS)