Extraordinary diversity of the CD28/CTLA4 family across jawed vertebrates.

Members of the CD28 family are critical for the control of immune cell activation. While CD28 and CTLA4 were previously identified in teleost fish, most members of the CD28 family have been described only in tetrapods. Using a comparative genomics approach, we found (co)orthologs of all members of the CD28 family both in Chondrichthyes and basal Osteichthyes groups, but not in Agnathans.

TLR7 in channel catfish (Ictalurus punctatus) is expressed in the endolysosome and is stimulated by synthetic ssRNA analogs, imiquimod, and resiquimod.

Toll-like receptors (TLRs) are pivotal pattern recognition receptors (PRRs) and key mediators of innate immunity. Despite the significance of channel catfish (Ictalurus punctatus) in comparative immunology and aquaculture, its 20 TLR genes remain largely functionally uncharacterized. In this study, our aim was to determine the catfish TLR7 agonists, signaling potential, and cellular localization.

Costimulatory receptors in the channel catfish: CD28 family members and their ligands.

The CD28-B7 interaction is required to deliver a second signal necessary for T-cell activation. Additional membrane receptors of the CD28 and B7 families are also involved in immune checkpoints that positively or negatively regulate leukocyte activation, in particular T lymphocytes. BTLA is an inhibitory receptor that belongs to a third receptor family.

A subset of leukocyte immune-type receptors (LITRs) regulates phagocytosis in channel catfish (Ictalurus punctatus) leukocytes.

Channel catfish, Ictalurus punctatus, leukocyte immune-type receptors (LITRs) constitute a large family of paired, immunoregulatory receptors unique to teleosts. A role for LITRs in phagocytosis has been proposed based on studies in mammalian cell lines; however, LITR-mediated phagocytosis has not been examined in the catfish model. In this study, we use two anti-LITR monoclonal antibodies, CC41 and 125.