Clinical and pathologic differences in interstitial lung disease based on antisynthetase antibody type

BACKGROUND

Interstitial lung disease (ILD) is a common extramuscular manifestation of the idiopathic inflammatory myopathies (IIMs), dermatomyositis (DM) and polymyositis (PM). Patients with antisynthetase antibodies (ASA) demonstrate some or all of the features of the antisynthetase syndrome including IIM and ILD. It has been hypothesized that the clinical expression of antisynthetase syndrome varies between specific ASAs.

OBJECTIVE

We sought to determine whether the myositis-associated ILD (MA-ILD) phenotype differs based on the presence of ASAs and by ASA subtype.

METHODS

A cross-sectional and longitudinal analysis of consecutive patients enrolled at the Johns Hopkins Myositis Center with ILD in the setting of clinically diagnosed autoimmune myositis was conducted.

RESULTS

Seventy-seven subjects were included; 36 were ASA negative, 28 were anti-Jo1 positive, and 13 were non-Jo1 ASA positive (5 anti-PL-12, 4 anti-PL-7, 2 anti-EJ, and 2 anti-OJ). Non-Jo1 ASA positive participants were more likely to be African-American than Caucasian as compared to both the anti-Jo1 positive (p = 0.01) and ASA negative groups (p < 0.01). ASA negative participants had better mean forced vital capacity percent predicted (FVC%) and total computed tomography scores over time compared to those with anti-Jo1 after controlling for potential confounders.

CONCLUSIONS

ASA status was significantly different by race. Those with anti-Jo1 antibodies had worse lung function and CT scores over time compared to those without detectable antisynthetase antibodies. Further prospective study in a larger cohort is needed to determine whether these apparent antibody-specific differences in demographics and manifestations of disease translate into meaningful disparities in clinical outcomes.

Green fluorescent protein is a quantitative reporter of gene expression in individual eukaryotic cells

Green fluorescent protein (GFP) has gained widespread use as a tool to visualize spatial and temporal patterns of gene expression in vivo. However, it is not generally accepted that GFP can also be used as a quantitative reporter of gene expression. We report that GFP is a reliable reporter of gene expression in individual eukaryotic cells when fluorescence is measured by flow cytometry. Two pieces of evidence support this conclusion: GFP fluorescence increases in direct proportion to the GFP gene copy number delivered to cells by a replication-defective adenovirus vector, Ad.CMV-GFP, and the intensity of GFP fluorescence is directly proportional to GFP mRNA abundance in cells. This conclusion is further supported by the fact that the induction of GFP gene expression from two inducible promoters (i.e., the TRE and ICP0 promoters) is readily detected by flow cytometric measurement of GFP fluorescent intensity. Collectively, the results presented herein indicate that GFP fluorescence is a reliable and quantitative reporter of underlying differences in gene expression.