HTLV-1 Impact on RA T-Cell Phenotypes

For HAS-Flow analysis, whole blood samples in EDTA tubes were obtained periodically from 57 participants with HTLV-1-positive RA and 13 participants with HTLV-1-negative RA. HAS-Flow analysis was performed to detect the expression levels of CADM1 and CD7 in CD4+ T-lymphocytes, according to previously reported methods [11 (link)]. An unlabelled CADM1 antibody (clone 3E1) was purchased from MBL (Tokyo, Japan) and subjected to primary amine biotinylation using biotin N-hydroxysuccinimide ester (Sigma Aldrich, St. Louis, MO, USA). All other antibodies were obtained from BioLegend (San Diego, CA, USA). Cells were stained using a combination of biotin-CADM1, allophycocyanin-CD7, and PE-Cy7-CD4. After washing, phycoerythrin (PE)-conjugated streptavidin was applied. A FACS Calibur instrument (BD Immunocytometry Systems, San Jose, CA, USA) was used for all multicolour flow cytometry. Data were analyzed using the FlowJo software (TreeStar, San Carlos, CA, USA).