Rat frozen spleen section was fixed with 4% paraformaldehyde (PFA) for ten minutes at room temperature and blocked with 5% FBS for 30 minutes at room temperature. Then the section was stained with 10 µg/mL of CD11b/c (clone OX-42) Alexa Fluor® 488 (green), 10 µg/mL of CD3 (clone 1F4) Alexa Fluor® 647 (blue), and 10 µg/mL of purified CD38 (clone 14.27) overnight at 4°C, followed by 5 µg/mL of anti-mouse IgG2b (clone RMG2b-1) Alexa Fluor® 594 (red) for two hours at room temperature. The image was captured by 10X objective.