Immunohistochemistry of CXCR5 in non-rheumatoid arthritis synovia. (a) CD68 staining in the intimal layer. (b) Serial section to (a) treated with anti-CXCR5, showing that CXCR5+ cells in the intimal layer included those also positive for CD68. (c) and (d) Sections from the same region as (a) and (b), treated with isotype-matched control immunoglobulin instead of CD68 and CXCR5 antibodies, respectively. (e) Subintimal postcapillary venule stains for CXCR5 expression (arrow). (f) Isotype-matched control for (e). Labelling was revealed using 3,3'-diaminobenzidine substrate. (a), (b), (e) and (f) Original magnification, 420 ×; (c) and (d) original magnification, 350 ×.