Elements of angiotensin system are involved in leeches and mollusks immune response modulation.

We present immunocytochemical, biochemical and cellular evidences for the presence of a renin-angiotensin system (RAS) in coelomocytes of invertebrates (leech, Theromyzon tessulatum and mollusk Mytilus edulis). Leech coelomocytes are immunoreactive to polyclonal antisera raised against the T. tessulatum angiotensin-converting enzyme (ACE) and leech brain angiotensin II (AII) and a commercial anti-AT1 receptor. Biochemically, renin, ACE- and AT1-like receptor were identified in the leech immune cells. We further demonstrate that leech AII (10(-6) M) alone does not initiate nitric oxide (NO) release in invertebrate immunocytes but does only after pre-exposing the cells to IL-1 (15.9+/-2.6 nM; P<0.005 vs. 1.1 nM when AII is added alone). Similar results were obtained with human leukocytes (14.5+/-2.7 nM; P<0.005 IL-1+AII vs. 0.9 nM when AII is added alone). Then, an immunocytochemical study performed at the structural and ultrastructural levels confirmed the presence in same immune cells all the molecules of the renin-angiotensin system (RAS) in leeches as epitopes to IL-1-like protein and IL-1-like receptor. This is the first report in invertebrates and of a co-action between cytokines like substances and neuropeptides in an immune process and the involvement of the RAS in modulation of the immune response.