Leukocyte immune-type receptors are markers of antiviral cytotoxic T lymphocytes in channel catfish, Ictalurus punctatus (VET1P.1125)

Abstract

Abstract LITRs are a multigene family in teleosts that encode immunoglobulin superfamily receptors with activating or inhibitory signaling capability, but their functional role in the immune response is not well understood. These immunoregulatory receptors exhibit sequence homology to both Fc receptors and molecules encoded in the leukocyte receptor complex. By using a combination of immunoprecipitation and protein identification by LC-MS/MS, we determined that the monoclonal antibody CC41 binds to LITRs on clonal cytotoxic T lymphocytes (CTL). Consequently, we hypothesize that this antibody can be used to monitor the in vivo antiviral CTL response. To test this hypothesis, we injected gynogenetic catfish with a channel catfish virus (CCV)-infected MHC-matched clonal T cell line (G14D-CCV) and collected peripheral blood lymphocytes (PBL) at 3, 5, and 9 days after injection for analyses by flow cytometry. The percentage of CC41+ cells was elevated five days after primary immunization and three days after booster immunization. When the CC41+ cell population was magnetically isolated from the PBL, they were found to specifically kill CCV-infected targets, as shown by 51Cr-release assays, and this killing is partially inhibited by the addition of CC41. When subjected to flow cytometric mRNA analyses, the CC41+ cells were found to express message for CD3γδ, perforin, and eomesodermin (EOMES), indicating that these cells are in fact CTL.