P1138FLOW CYTOMETRIC ANALYSIS ON LYMPHOCYTE SUBSETS APPEARED IN PERITONEAL DIALYSIS EFFLUENT IN RELATION WITH PERITONEAL FUNCTION
Authors: Ohashi Atsuki , Kondo Madoka , Ihara Fumitaka , Toshima Noriyuki , Ohara Yoshitatsu , Tanaka Tomomi , Maeda Yoshitaka 
Published: June 2020

Abstract

Background and Aims
We previously reported that an increase of lymphocytes in peritoneal dialysis (PD) effluent was correlated with risk of encapsulating peritoneal sclerosis (EPS). In the present study, we analyzed subsets of lymphocytes in PD effluent by flow cytometry and evaluated their changes every six month to elucidate the etiological background of peritoneal dysfunction.

Method
We enrolled patients who started PD between 2006 and 2017, and of whom the data for PET and flow cytometric analysis was available at least for three consecutive times with an interval of six months. We excluded the patients who experienced PD peritonitis during the observation period. Consequently, the levels and changes of lymphocyte subset, such as CD4+/CD8+ naïve T cell (CCR7+/CD45RA+), CD4+/CD8+ central memory T cell (CCR7+/CD45RA-), CD4+/CD8+ effector memory T cell (CCR7-/CD45RA-), CD4+/CD8+ terminally differentiated effector memory T cell (CCR7-/CD45RA+), D/P creatinine ratio, FSC ratio of mesothelial cells and lymphocytes (a possible indicator for mesothelial cell size) were analysed in 23 patients over one year.

Results
We evaluated whether the observed variables on the first evaluation (six months after initiation of PD) affected the changes of D/P creatinine and FSC ratio over one year by a simple linear regression analysis. In the examined variables, only a fraction of CD8+ central memory T cell was significantly correlated with the change rate of D/P creatinine ratio (β=1.47, p=0.001, adjusted R2=0.379). We also evaluated whether the change rate of observed variables was correlated with the change rate of D/P creatinine and FSC ratio by a simple linear regression analysis. A fraction of CD8+ naïve T cell or CD8+ central memory cell was negatively correlated with the change rate of D/P creatinine ratio (naïve T cell; β=-0.058, p=0.022, adjusted R2=0.188, central memory T cell; β=-0.096, p=0.046, adjusted R2=0.137). The change rate of CD8+ effector memory T cell was not significantly correlated with the change rate of D/P creatinine ratio (β=0.172, p=0.096, adjusted R2=0.085). However, the change rate of D/P creatinine ratio tends to be higher in accordance with the increased change rate of CD8+ effector memory T cell by One way ANOVA, where the change rate was divided into three groups in descending order (p=0.0796) (Fig.1). Besides, the change rate of CD8+ effector memory T cell tends to be higher in accordance with the increased fraction of CD8+ central memory T cell at the first evaluation by Kruskall-Wallis test, where the change rate was divided into three groups in descending order (p=0.169) (Fig.2).

Conclusion
A decrease in the fraction of CD8+ naïve or central memory T cell was significantly correlated with the increase of D/P creatinine ratio. An Increase in the fraction of CD8+ effector memory T cell was also possibly correlated with the increase of D/P creatinine ratio, although it was not statistically significant (p=0.096). An initial fraction of CD8+ central memory T cell was significantly correlated with the change rate of D/P creatinine ratio. From these results, central memory T cells and naïve T cells at an initial stage may be transformed into effector memory T cells by repeated exposure to unknown antigens derived from PD solution and these effector memory T cells may damage the peritoneum to increase D/P creatinine ratio. An initial higher fraction of CD8+ central memory T cell suggested an acceleration in the transformation into CD8+ effector memory T cell.