Chemokine receptor co-expression reveals aberrantly distributed TH effector memory cells in GPA patients

BACKGROUND Persistent expansion of circulating CD4+ effector memory T cells (TEM) in patients with granulomatosis with polyangiitis (GPA) suggests their fundamental role in disease pathogenesis. Recent studies have shown that distinct functional CD4+ TEM cell subsets can be identified based on expression patterns of chemokine receptors. The current study aimed to determine different CD4+ TEM cell subsets based on chemokine receptor expression in peripheral blood of GPA patients. Identification of particular circulating CD4+ TEM cells subsets may reveal distinct contributions of specific CD4+ TEM subsets to the disease pathogenesis in GPA. METHOD Peripheral blood of 63 GPA patients in remission and 42 age- and sex-matched healthy controls was stained immediately after blood withdrawal with fluorochrome-conjugated antibodies for cell surface markers (CD3, CD4, CD45RO) and chemokine receptors (CCR4, CCR6, CCR7, CRTh2, CXCR3) followed by flow cytometry analysis. CD4+ TEM memory cells (CD3+CD4+CD45RO+CCR7-) were gated, and the expression patterns of chemokine receptors CXCR3+CCR4-CCR6-CRTh2-, CXCR3-CCR4+CCR6-CRTh2+, CXCR3-CCR4+CCR6+CRTh2-, and CXCR3+CCR4-CCR6+CRTh2- were used to distinguish TEM1, TEM2, TEM17, and TEM17.1 cells, respectively. RESULTS The percentage of CD4+ TEM cells was significantly increased in GPA patients in remission compared to HCs. Chemokine receptor co-expression analysis within the CD4+ TEM cell population demonstrated a significant increase in the proportion of TEM17 cells with a concomitant significant decrease in the TEM1 cells in GPA patients compared to HC. The percentage of TEM17 cells correlated negatively with TEM1 cells in GPA patients. Moreover, the circulating proportion of TEM17 cells showed a positive correlation with the number of organs involved and an association with the tendency to relapse in GPA patients. Interestingly, the aberrant distribution of TEM1 and TEM17 cells is modulated in CMV- seropositive GPA patients. CONCLUSIONS Our data demonstrates the identification of different CD4+ TEM cell subsets in peripheral blood of GPA patients based on chemokine receptor co-expression analysis. The aberrant balance between TEM1 and TEM17 cells in remission GPA patients, showed to be associated with disease pathogenesis in relation to organ involvement, and tendency to relapse.