Abstract P280: Type V Collagen is a Lung-Associated Self-Antigen Uncovered by Chronic Hypoxia

Abstract

Hypoxic pulmonary hypertension (PH) is a progressive and often fatal consequence of chronic hypoxia (CH) exposure (chronic lung diseases, high altitude and sleep apnea). We recently demonstrated that T helper 17 (T H 17) cells are localized in the perivascular region of pulmonary arteries and contribute to CH-induced PH, at least in part, by causing pulmonary arterial (PA) remodeling. Naturally occurring “nT H 17” cells, can be detected as early as week 17 of fetal life in humans, and are in homeostatic equilibrium with natural T regulatory (nTregs) cells. nT H 17 cells are specific for a limited range of self-antigens, including type V collagen (colV). ColV is normally sequestered within type I col in the extracellular matrix of the lungs hidden from the immune system. Activation of matrix metalloproteinase-2, which is induced by CH, can expose colV. Therefore, we tested the hypothesis that ColV is a lung-associated self-antigen uncovered by CH. We found colV immunoreactivity only in lungs from mice exposed to hypobaric CH for 5 days vs. controls and colV mRNA expression is significantly increased in isolated PA (log fold change mean±SEM, normoxia= 0.22±0.08 vs. CH=0.48±0.02, n=3, p=0.02) suggesting that CH uncovers hidden colV. We then, determined cellular autoimmunity to colV using a trans-vivo delayed-type hypersensitivity assay (TV-DTH). Splenocytes obtained from 5 days CH-exposed mice displayed a TV-DTH colV response significantly higher than that from normoxic mice (footpad swelling [10 -4 ”] normoxia=11.8±1.1 vs. CH= 35.6±3.0, n=14, p=0.0001), while there was minimal response to col I. To determine that reactivity to colV contributes to CH-induced PH, we induced peripheral tolerance to colV by administering 25 μl of 0.08 μg/μl of bovine colV (Sigma) in PBS in each nare or PBS every two days for two weeks prior and during CH (21 days). Right ventricular systolic pressure (RVSP) was higher in vehicle-treated compared to colV-treated mice (mmHg CH vehicle= 32.4±0.3 vs. CH colV= 27.8±0.9, n=4, p=0.0085) suggesting that oral tolerance to col V attenuated PH. These results are ground-breaking suggesting that acute autoreactivity to colV develops after exposure to hypoxia. Next, we will determine whether a disrupted balance of nTh17/nTreg mediates this response.