Abstract
We have reported that B cell differentiation factor (BCDF) might contribute to the immunological abnormalities in lupus erythematosus, one of autoimmune diseases. In order to clarify the role of BCDF in autoimmune Hashimoto's thyroiditis, we examined autoantibody production by B cells in response to recombinant B cell stimulatory factor-2 (BSF-2).
B cells of peripheral blood from patients with Hashimoto's thyroiditis and normal controls were separated by Ficoll-Conray density centrifugation, adhesion to FCS-coated Petri dishes and E-rosetting. Hundred thousands B cells were cultured with 0_??_40 U/ml BSF-2 for 3_??_12 days in microculture plates. Anti-thyroglobulin antibody (anti-Tg) and total IgG in culture supernatant were assayed by sensitive Biotin-Avidin ELISA and conventional ELISA, respectively. Results were expressed as ELISA Index based on a standard serum. Coefficients of variation of intra-assay and interassay were 8.0 and 10.7% respectively.
When the effect of BSF-2 (0_??_40 U/ml) on B cells for the production of anti-Tg was tested, apparent stimulatory effect of BSF-2 was observed at the concentration of 10 U/ml and 20 U/ml. Since there was no significant difference between 10 and 20 U/ml, 20 U/ml of BSF-2 was used for the following experiments.
Kinetics analysis of anti-Tg production was studied in the presence or absence of BSF-2 up to 12 days. Although normal B cells did not produce anti-Tg, Hashimoto's B cells produced significant amount of anti-Tg in response to BSF-2 at 9 days (30.3±4.1 vs. 22.3±3.9 ELISA Index, p<0.05). Total IgG production by Hashimoto's or normal B cells were not enhanced by BSF-2 stimulation. These result suggested that peripheral blood B cells from patients with Hashimoto's thyroiditis are already activated for the production of anti-Tg in vivo and responded to BSF-2 without any pre-treatment.
