Role of major histocompatibility complex II antigen‐presentation pathway genes in orange‐spotted grouper infected with Cryptocaryon irritans

Abstract

Cryptocaryon irritans, a pathogen model for fish mucosal immunity, causes skin mucosal and systematic humoral immune response. Where and how MHC II antigen presentation occurs in fish infected with C. irritans remain unknown. In this study, the full‐length cDNA of the grouper cysteine protease CTSS was cloned. The expression distributions of six genes (CTSB, CTSL, CTSS, GILT, MHC IIA and MHC IIB) involved in MHC II antigen presentation pathway were tested. These genes were highly expressed in systematic immune tissues and skin and gill mucosal‐associated immune tissues. All six genes were upregulated in skin at most time points. Five genes expected CTSS was upregulated in spleen at most time points. CTSB, CTSL and MHC IIA were upregulated in the gill and head kidney at some time points. These results indicate that the presentation of MHC II antigen intensively occurred in local infected skin and gill. Spleen, not head kidney, had the most extensive systematic antigen presentation. In skin, six genes most likely peaked at day 2, earlier than in spleen (5–7 days), marking an earlier skin antibody peak than any recorded in serum previously. This significant and earlier mucosal antigen presentation indicates that specific immune response occurs in local mucosal tissues.

Host responses against the fish parasitizing ciliate Cryptocaryon irritans

“…It was interesting to find that all these signalling molecules were up‐regulated in the infected local mucosal sites (skin and gill) at most tested time points. In the same study, with the presence of C. irritans in the skin and gill of E. coioides , upregulated expression of histocompatibility complex II ( MHC II ) was detected 38 . The results mentioned above might suggest that the increased accumulation of IgT + B cells, CD8α + cells and MHC II‐positive cells in the skin and gill of E. coioides after they were infected with C. irritans .…”

“…In the same study, with the presence of C. irritans in the skin and gill of E. coioides, upregulated expression of histocompatibility complex II (MHC II) was detected. 38 The results mentioned above might suggest that the increased accumulation of IgT + B cells, CD8α + cells and MHC II-positive cells in the skin and gill of E. coioides after they were infected with C. irritans. Nevertheless, in view of the fact that upregulated mRNA expression of these genes does not mean that they are also up-regulated at protein level, further functional studies of these proteins may be required.…”

Comprehensive transcriptomics and proteomics analysis of Carassius auratus gills in response to Aeromonas hydrophila

“…Similarly, a study of the molecular mechanism in the gills of O. mykiss by using transcriptome analysis found that some increased immune-related genes were significantly related with antigen processing and presentation in the infected gills [ 13 ]. Several antigen processing and immune-relevant proteins included major histocompatibility complex (MHC I/II), heat shock proteins (Hsp70/90A/A1) and calreticulin (CALR/3b) were crucial for the host immune defense against bacterial infection [ 9 ]. The MHC molecules may have participated in antigen presentation for specific immunity by modulating mechanism through interactions with T-lymphocyte and Natural killer cells in animals [ 13 , 43 ].…”

“…The evidences indicated that fish gill tissue provides major point of entry for pathogens and attachment sites [ 8 ]. And a great deal of immune-relevant genes participate in the gill local immune response, adding its most important function for immune response and survival in fish [ 6 , 9 , 10 ]. Previous studies demonstrated that several key immune-related genes such as tumor necrosis factor [ 6 ], interleukins [ 11 ] , heat shock proteins [ 12 ], major histocompatibility complex [ 9 ] and complements [ [10] , [13] , [14] ] were identified with respect to the involvement in immune defenses of gills.…”

“…And a great deal of immune-relevant genes participate in the gill local immune response, adding its most important function for immune response and survival in fish [ 6 , 9 , 10 ]. Previous studies demonstrated that several key immune-related genes such as tumor necrosis factor [ 6 ], interleukins [ 11 ] , heat shock proteins [ 12 ], major histocompatibility complex [ 9 ] and complements [ [10] , [13] , [14] ] were identified with respect to the involvement in immune defenses of gills. Nevertheless, the precise mechanisms of gill immune response to bacterial-infection were still unclear in fish, and applying in-depth research and analysis to achieve better outcomes were required for the immunological system of the cyprinid species, and signaling pathways implicated in its immune response following exposure to the bacteria [ 8 ].…”