Immunosuppressive Effects of Annona muricata L. Leaf Extract on Cellular and Humoral Immune Responses in Male Wistar Rats

Background: Annona muricata L. (Annonaceae) (AM)'s remarkable anti-inflammatory and anti-cancer activities make it a targeted plant to be explored for its immunomodulatory properties. Traditional practitioners have employed various components of AM to cure a variety of ailments, including cancer, diabetes, and inflammation. Objective: The present study evaluated the immunosuppressive effects of 80% ethanol extract of of AM leaves in male Wistar rats on different parameters of humoral and cellular immune responses. Methods: AM leaf extract (AMLE) was analyzed using UHPLC-MS/MS to profile its secondary metabolites. AMLE was rich in polyphenols which include (epi)catechin-(epi)catechin-(epi) catechin, caffeic acid, coumaroylquinic acid, hyperin, kaempferol, quinic acid and rutin. The rats were administered 100, 200 and 400 mg/kg bw of the extract daily for 14 days. The effects of AMLE on innate immune responses were determined by evaluating phagocytosis, neutrophils migration, reactive oxygen species (ROS) release, CD11b/CD18 integrin expression, and ceruloplasmin, lysozyme and myeloperoxidase (MPO) levels. The adaptive immune parameters were evaluated by immunizing the rats with sheep red blood cells (sRBC) on day 0 and administered orally with AMLE for 14 days. Results: AMLE established significant immunosuppressive effects on the innate immune parameters by inhibiting the neutrophil migration, ROS production, phagocytic activity and expression of CD11b/CD18 integrin in a dose-dependent pattern. AMLE also suppressed ceruloplasmin, MPO and lysozyme expressions in the rat plasma dose-dependently. AMLE dose-dependently inhibited T and B lymphocytes proliferation, Th1 and Th2 cytokine production, CD4⁺ and CD8⁺ co-expression in splenocytes, immunoglobulins (IgM and IgG) expression and the sRBC-induced swelling rate of rat paw in delayed-type hypersensitivity (DTH). Conclusion: The strong inhibitory effects on the different parameters of humoral and cellular responses indicate that AMLE has potential to be an important source of effective immunosuppressive agents.