Having an absent or non-functional spleen means a person is susceptible to encapsulated bacteria - like Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, and Salmonella species - since encapsulated bacteria are normally opsonized and then phagocytized by macrophages in the spleen.

无脾或脾功能丧失使人容易感染荚膜菌，例如肺炎链球菌、流感嗜血杆菌、脑膜炎奈瑟菌与沙门氏菌，因为荚膜菌通常被脾脏中的巨噬细胞调理并吞噬。