Peripheral blood immune cell profiles of corneal transplant with and without acute rejection

Acute rejection (AR) of corneal transplants (CT) has a profound effect on subsequent graft survival but detailed immunological studies in human CT recipients are lacking. In this multi-site, cross-sectional study, clinical details and blood samples were collected from adults with clinically-diagnosed AR of full thickness (FT)-CT (n=35) and posterior lamellar (PL)-CT (n=21) along with Stable CT recipients (n=177) and adults with non-transplanted corneal disease (n=40). For those with AR, additional samples were collected 3 months later. Immune cell analysis was performed by whole-genome microarrays (whole blood) and high dimensional multi-color flow cytometry (peripheral blood mononuclear cells). For both, no activation signature was identified within the B cell and T cell repertoire at the time of AR diagnosis. Nonetheless, in FT- but not PL-CT recipients, AR was associated with differences in B cell maturity and regulatory CD4+ T-cell frequency compared to stable allografts. Our results suggest that, in contrast to solid organ transplants, genetic or cellular assays of peripheral blood are unlikely to be clinically exploitable for prediction or diagnosis of AR. However, further investigation of circulating B cell and T cell subpopulations may provide insights into the regulation of anti-donor immune response in human CT recipients with differing AR risk. Microarray gene expression profiling of a subset of 330 samples from 263 corneal transplant (CT) patients and 28 healthy volunteers (301 subjects total) was performed using Affymetrix Clariom S arrays. Corneal transplants were either full thickness (FT) or posterior lamellar (PL). Differential expression analysis of transcriptomic profiles from samples taken at the enrolment visit (baseline) was performed comparing FT-CT and PL-CT patients with Acute Rejection (n=34) to those with stable CTs (n=87). In addition, a paired comparison was performed between FT-CT patients with acute rejection sampled at the time of acute rejection diagnosis relative to 3 months after (13 pairs).