LAUSR

We read with interest the research letter by Raychaudhuri et al , which examines the frequencies of cytokine producing CD4+ memory T cells in psoriatic arthritis (PsA) and rheumatoid arthritis (RA) synovial fluid mononuclear cells (SFMC) compared with peripheral blood mononuclear cells (PBMC).1 The authors examined the frequencies of single cytokine-producing T cells, specifically interleukin (IL)-17A+, IL-22+, tumour necrosis factor (TNF)+, interferon gamma (IFNγ)+ or IL-23R+ and report that Th17 cells are enriched in PsA SFMC, while RA is skewed to a Th1-like profile. In our previous publication, Wade et al ,2 we reported the frequencies of both single cytokine-producing and multiple cytokine (polyfunctional)-producing T cells, in addition to the frequencies of Th1, Th17 and exTh17 cells by using the Th17 lineage marker CD161. In our study, however, we reported these findings in synovial tissue biopsies from PsA patients, as opposed to …