Development of a Monoclonal Antibody Specific to the IgM Heavy Chain of Bighead Catfish (<i>Clarias macrocephalus</i>): A Biomolecular Tool for the Detection and Quantification of IgM Molecules and IgM⁺ Cells in <i>Clarias</i> Catfish

• Main Authors: Anurak Bunnoy, Uthairat Na-Nakorn, Prapansak Srisapoome
• Format: Article
• Language: English
• Published: MDPI AG 2020-04-01
• Series: Biomolecules
• Subjects: monoclonal antibody; IgM heavy chain; catfish; ELISA; flow cytometry; B cells
• Online Access: https://www.mdpi.com/2218-273X/10/4/567

Catfish is a commonly-cultivated freshwater fish in Thailand and many Southeast Asian countries. The molecular data obtained for the IgM heavy chain (IgMH) of catfish have been useful for distinguishing monoclonal antibodies (mAbs). A mAb specific to Cμ₁ of the IgMH of catfish (IgMHCμ₁ mAb) was developed in a rabbit model using sequence information from bighead catfish (<i>Clarias macrocephalus</i>). The IgMHCμ₁ mAb strongly recognized the IgM heavy chain of the tested catfish, namely, bighead catfish, African catfish (<i>Clarias gariepinus</i>) and their hybrid (<i>C. macrocephalus</i> × <i>C. gariepinus</i>), in immunological Western blot analysis and competitive ELISAs. Additionally, the IgMHCμ₁ mAb successfully recognized IgM⁺ cells by detecting IgM molecules in both secreted and membrane-bound forms in peripheral blood leukocytes (PBLs). The IgMHCμ₁ mAb was further used to quantify the percentage of IgM⁺ cells among PBLs through flow cytophotometry. The IgM⁺ cell percentages of healthy bighead catfish, African catfish and their hybrid were 38.0–39.9%, 45.6–53.2%, and 58.7–60.0%, respectively. Furthermore, the IgMHCμ₁ mAb showed no cross-reactivity with the IgM of zebrafish. These findings suggest that this mAb can be used as an immunological tool for monitoring the health, immune status, and immune development of cultivated <i>Clarias</i> catfish.