[Establishment and identification of a C57B/6 mouse sarcoidosis granuloma model].

Objective: To establish a C57BL/6 mouse sarcoidosis granuloma model elicited by mycobacterial superoxide dismutase A peptide (SodA).
Methods: Thirty female C57BL/6 mice were randomly divided equally into 5 groups: a combination (SodA+Sepharose) group, a SodA group, a IFA (incomplete Freund's adjuvant) group, a sepharose group and a blank control group. On the first day, the combination group and the SodA group were sensitized by subcutaneous injection of 50 µg SodA incorporated into IFA 0.25 ml. The IFA group and the Sepharose group were treated with subcutaneous injection of IFA 0.25 ml and PBS 0.25 ml respectively, while the blank control group was not given any treatment. On the 14th day, the combination group was challenged by tail vein injection of 50 µg SodA covalently coupled to 6000 agarose 4B beads (in PBS 0.5 ml) . The SodA group was challenged by tail-vein injection of 50 µg SodA (in PBS 0.5 ml) . The IFA group and the Sepharose group were treated by tail-vein injection of 6000 agarose 4B beads (in PBS 0.5 ml) , while the blank control group was not given any treatment. On the 22th day, the mice were dissected and the gross and pathological changes of lymph nodes and lungs were observed. Immunohistochemisty was used to identify Mac-2 and CD(+)4T in granuloma. Counts and differentials of BALF cells were measured. CD(+)4/CD(+)8 in BALF and cytokines (IFN-γ and IL-12 ) levels in the lungs were detected by flow cytometry.
Results: Enlargement of peripheral and pulmonary hilar lymph nodes were found in the combination group and the SodA group, and sarcoidosis granuloma was found in the lymph nodes and lungs of the combination group. Sarcoidosis granuloma was also found in the lymph nodes but not in the lungs of the SodA group. No sarcoidosis granuloma was observed in the lungs and lymph nodes of the IFA group, the Sepharose group and the blank control group. Macrophage specific antigen Mac-2 and CD(+)4T were positive in the core and rim of the granuloma respectively. The lymphocyte percentages in the BALF of the combination group and the SodA group [(19.4 ± 6.5)% and (22.3 ± 8.5)%] were significantly higher than that in the IFA group, the Sepharose group and the blank control group [(8.5 ± 4.3)%, (7.7 ± 3.4)%, (0.8 ± 0.6%)] (P < 0.05 ). CD(+)4/CD(+)8 in the BALF of the combination group and the SodA group (3.5 ± 1.4, 3.2 ± 1.1) were significantly higher than that in the IFA group and the Sepharose group (1.2 ± 0.5, 1.0 ± 0.4) (P < 0.05 ). IFN-γ and IL-12 in the lungs of the combination group and the SodA group [IFN-γ:(32.9 ± 9.7) ng/L, (26.4 ± 7.2) ng/L; IL-12: (29.6 ± 9.4) ng/L, (26.1 ± 8.9) ng/L]were significantly higher than those of the IFA group, the Sepharose group and the blank control group [IFN-γ: (16.5 ± 6.8) ng/L, (12.2 ± 5.0) ng/L, (9.0 ± 2.6) ng/L; IL-12: (16.7 ± 4.6) ng/L, (13.6 ± 4.4) ng/L, (9.6 ± 5.3) ng/L] (P < 0.05 ). But these indexes were not significantly different between the combination group and the SodA group, and among the IFA group, the Sepharose group and the blank control group (P > 0.05).
Conclusion: SodA can elicit sarcoidosis granuloma in C57BL/6 mice, and the immunological features of the model were similar to those in human sarcoidosis.