Immune Reconstitution Analysis of Patients Undergoing Extracorporeal Photopheresis for the Treatment of Chronic Graft-Versus-Host Disease

Allogeneic blood and marrow transplantation for the treatment of hematologic malignancies continues to be plagued by complications such as chronic graft-versus-host disease (cGVHD), which can occur in upwards of 50% of patients. Standard therapy involves corticosteroid administration, which is not always effective and impedes the patient’s return to a completely competent immune system, thus increasing the risk of infectious complications. Extracorporeal photopheresis (ECP) has been successfully used to abate cGVHD symptoms in many patients. The effect this therapy has on lymphocyte subsets in the reconstituting immune compartment has yet to be fully ascertained. In the present study, we used flow cytometric analysis to examine lymphocyte subsets in patients undergoing ECP for the treatment of cGVHD. Peripheral blood was collected from 5 patients prior to starting ECP and after 90 days of treatment. CD4⁺ T cell populations were analyzed for expression of CD45RA and CCR7 to classify naïve (RA⁺, CCR7⁺), central memory (T^CM; RA^-, CCR7⁺), effector memory (T^EM; RA^-, CCR7^-), and terminally differentiated effector memory (T^EMRA; RA⁺, CCR7^-) T cells. The data reported supports previous studies which show that all CD4⁺ T cell populations analyzed are altered in cGVHD patients (n=11) compared to healthy controls (n=5). In particular, CD4⁺ T^CM and naïve cells were decreased in cGVHD patients, while CD4⁺ T^EM and T^EMRA were elevated in these patients. Analysis of the same subsets in cGVHD patients after 90 days of ECP treatment revealed that the percentage of CD4⁺ T^CM increased above baseline levels in the 5 cGVHD patients examined, while CD4⁺ T^EMRA were decreased during the same time frame. The increase in CD4⁺ T^CM and the decrease in CD4⁺ T^EMRA were statistically significant as determined by the paired Student’s t test. Additionally, the ratio of CD4⁺ T^CM to T^EM and CD4⁺ T^CM to T^EMRA was calculated in patients before and after ECP treatment. Results indicate significantly increased ratios of both T^CM:T^EM and CD4⁺ T^CM:T^EMRA in these patients as well. This data strongly supports the role of ECP in the normalization of CD4⁺ T cell populations in cGVHD patients.