CD28 and rheumatoid arthritis: However, we did not notice any significant difference in the percentages of CD8+CD45RO−CD28− effectors, CD8+CD45RO+CD28− effector memory, CD8+CD45RO+CD28+ central memory or CD8+CD45RO−CD28+ naïve T cells (Fig. 3c) among RA patients and the healthy donors18.