(A and B) Cryosections displaying NELO (red arrowheads) in adult zebrafish naturally coinfected with three parasite diseases (P. neurophilia, P. tomentosa, and M. streisingeri) labeled with anti-ZAP70 antibody (magenta hot). The distribution of ZAP70-positive cells in NELO appears more heterogeneous than in uninfected fish. In addition, some the labeled cells formed small clusters (cyan stars). (C and D) Cryosections from adult zebrafish bath-infected for 24 hours with IHNV. After the apparition of more prominent aggregations of ZAP70-positive cells at 3 dpi (yellow stars) (C), the distribution of T/NK cells reverted to a more homogeneous state by 10 dpi (D). (E and F) Cryosections from adult zebrafish bath-infected for 24 hours with SVCV. NELO displayed notable aggregations of T/NK cells into distinct clusters at 3 dpi (yellow stars) (E). A week later, NELO displayed both large (yellow star) and small clusters (cyan star) of ZAP70-positive cells (F). (G to J) Cryosections from zebrafish 3 day after SVCV infection co-labeled with anti-ZAP70 antibody (yellow) and anti-SVCV-N antibody (cherry), revealing cells loaded with viral material (cyan arrows) neighboring large clusters of ZAP70-positive cells. Annotations: dpi, day postinfection; IHNV, infectious hematopoietic necrosis virus; SVCV, spring viremia of carp virus. Scale bars, 50 (E), 30 (A to D and F), and 20 μm (G to J).