Additionally, an increase in lactate secretion by macrophages and monocytes not only upregulates the expression of pro-inflammatory cytokines IL-23 and IL-6, thereby promoting the proliferation of Th17 lymphocytes (a principal immune cell group in RA) (32), but also inhibits the migration of CD8+ and CD4+ T lymphocytes, causing their retention at the site of inflammation (33). Here, CD4 is linked to rheumatoid arthritis.