[Expression of major histocompatibility complex class II antigens on lungs in rat with bleomycin-induced pulmonary...

To explore the expression levels of MHC II molecules and its regulator genes CIITA on bleomycin-induced pulmonary fibrosis in rats, and to investigate the underlying immunologic mechanisms of pulmonary fibrosis.

The rats were treated with either a single intratracheal bleomycin injection (fibrosis group) or a normal saline injection (control group). The pathologic changes of lung tissues stained with HE and Masson were observed, and the contents of hydroxyproline were detected on the 7th and 28th day respectively after bleomycin administration. The expression of MHC II molecules in the lung tissues was evaluated with immunohistochemistry techniques, and the percentage of MHC II+ cells was measured. The amounts of total CIITA and type I, III and IV CIITA mRNA of lung tissues were measured by real-time PCR using Taqman probe.

(1)The percentage of MHC II+ cells in lung tissues increased significantly in fibrosis group compared with that of control group on the 7th day and the 28th day [(0.10 +/-0.03) vs (0.06+/-0.02), P < 0.05; (0.15+/-0.03) vs (0.06+/-0.01),P < 0.01, respectively]; In fibrosis group, the percentage on the 28th day was higher than that on the 7th day [(0.15+/-0.03) vs (0.10+/-0.03), P < 0.05]; (2) Compared with control group on the 7th day, total CIIA mRNA increased 170.4% [(2.89+/-1.07) vs (1.07+/-0.46), P < 0.05], type I CIIA increased 258.8% [(0.77+/-0.38) vs (0.21+/-0.09), P < 0.05], while type IV CIITA decreased 87.2% [(0.39+/-0.15) vs (3.01+/-0.79), P < 0.01]; On the 28th day, total CIITA mRNA increased 98.6% [(4.14+/-1.15) vs (2.08+/-0.76), P < 0.05], type I CIIA increased 137.1% [(0.79+/-0.34) vs (0.33+/-0.23), P < 0.05], type IV CIITA mRNA still decreased, but there was no significant difference [(2.98 +/-0.92) vs (3.95+/-0.93), P > 0.05]; In fibrosis group, type IV CIIA mRNA was 667.3% [(2.98+/-0.92) vs (0.39+/-0.15), P < 0.01] higher on the 28th day than that on the 7th day; Type III CIIA mRNA levels of both groups had no significant difference.

MHC II/CIITA system of lung tissues was probably involved in the development of rat pulmonary fibrosis.