Immune-complex trapping in the splenic ellipsoids of rainbow trout (Oncorhynchus mykiss)

Abstract

Rainbow trout (Oncorhynchus mykiss), immunised with horseradish peroxidase, were given horseradish peroxidase intravenously, and the trapping of antigen in the spleen was followed 1, 24, and 48 h after injection. After 1 h, the localisation of horseradish peroxidase indicated that the antigen had been extensively trapped in the walls of the splenic ellipsoids. The colocalization of horseradish peroxidase with rainbow trout immunoglobulin M and complement factor 3 was shown with a double immunofluorescence technique and suggested that horseradish peroxidase was trapped in the form of immune complexes. After 24 and 48 h, very little horseradish peroxidase was detected in the ellipsoids, and horseradish peroxidase was mainly found in association with large cells with prominent cytoplasmic extensions. In non-immunized fish given horseradish peroxidase intravenously, antigen was not detected in ellipsoids. Thus, the observed difference between immunised and non-immunized trout suggests a specific role for the splenic ellipsoids in rapid immune-complex trapping and invites speculation on its significance in a secondary immune response.

The trapping of intravenously injected extracellular products fromAeromonas salmonicidain head kidney and spleen of vaccinated and nonvaccinated Atlantic salmon,Salmo salarL.

“…In rainbow trout immunised with horseradish peroxidase, Espenes et al (1995b) demonstrated that, one hour after intravenous injection, horseradish peroxidase was trapped in the form of immune complexes in the walls of splenic ellipsoids. In nonimmunised rainbow trout, antigen and complement factor 3 were detected in a few single cells in the spleen but neither antigen nor complement factor 3 was retained in the ellipsoids.…”

“…In the head kidney of carp, Cyprinus carpio L., human gamma globulin complexed with immunoglobulin was taken up more quickly than antigen alone (Secombes et al, 1982). In the spleen of rainbow trout, Oncorhynchus mykiss, the trapping of nonantigenic microparticles in ellipsoidal sheaths was related to the diameter of the particles (Espenes et al, 1995a), while the retention of soluble antigens, such as horseradish peroxidase, was dependent on the colocalisation of antigen, immunoglobulin and complement factor 3 (Espenes et al, 1995b).…”

A monoclonal antibody recognising a surface marker on rainbow trout (Oncorhynchus mykiss) monocytes

“…Shortly after injection of A. salmonicida the percentage of mab 45+ cells in blood increased whereas in spleen a decrease in the number of mab 45+ cells was measured between day 4 and day 7 post-injection. These kinetics are reminiscent of the activation of monocytes which migrate from spleen and blood to the peritoneal cavity to ingest the injected bacteria and move back to the spleen to present the processed A. salmonicida antigens to B-and T-lymphocytes in the melanomacrophage centres (Gutmundsdottir et al, 1995;Espenes et al, 1995) over a longer period. This might be due to the chemokine e#ects of the A-layer protein as shown in vitro by Weeks-Perkins & Ellis (1995).…”

The morphology of the immune system in teleost fishes

“…Ellipsoids appear to have a specialised function for plasma filtration and the trapping of blood-borne substances, particularly immune complexes (Ellis, 1980;Secombes & Manning, 1980;Espenes et al, 1995b) (Fig. 6).…”