IFN-γ is one of the key cytokines in defining Th1 immune responses. In this study, an IFN-γ homologue has been identified in rainbow trout Oncorhynchus mykiss, and its biological activities have been characterized. The trout IFN-γ cDNA is 1034 bp in length and translates into a 180-aa protein. The first intron of the trout IFN-γ gene contains highly polymorphic GACA minisatellites and 44-bp DNA repeats, giving rise to at least six alleles. IFN-γ is structurally conserved among vertebrates, and a signature motif has been identified. A nuclear localization sequence known to be crucial for IFN-γ biological activities is also present in the C-terminal region of the trout IFN-γ. The IFN-γ expression was induced in head kidney leukocytes by stimulation with PHA or poly(I:C) and in kidney and spleen of fish injected with poly(I:C). rIFN-γ produced in Escherichia coli significantly stimulated gene expression of IFN-γ-inducible protein 10 (γIP-10), MHC class II β-chain, and STAT1, and enhanced respiratory burst activity in macrophages. Deletion of 29-aa residues from the C terminus containing the nuclear localization sequence motif resulted in loss of activity with respect to induction of γIP-10 in RTS-11 cells. Moreover, IFN-γ-induced γIP-10 expression was completely abolished by the protein kinase C inhibitor staurosporine, and partially reduced by U0126, a specific inhibitor for ERKs. Taken together, the present study has demonstrated for the first time a functional IFN-γ homologue in a fish species, strongly suggesting a conserved Th1 immune response is most likely present in lower vertebrates.

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IL-15 is a member of the common γ-chain family of cytokines that possess a heterogeneous repertoire of activities on various cells of the immune system. We report here the first functional characterization of a fish IL-15 in rainbow trout. The trout IL-15 gene is 6-kb long and contains six exons and five introns that transcribe into a 1.2-kb mRNA containing seven out-of-frame AUG initiation codons and translate into a 193-aa peptide. Potential sites for transcriptional activators and repressors have been identified in the trout IL-15 gene. Like IL-15 from other species, trout IL-15 is closely linked to an INPP4B gene, but there is also a BCL10 gene located between the IL-15 and INPP4B genes. Three alternative splicing variants of the trout IL-15 gene have also been identified and their expression in vivo was studied. Trout IL-15 expression is present in all the tissues and cell lines studied. Recombinant trout IFN-γ selectively increased IL-15 expression but had little effect on other cytokines such as IL-1β and IL-11. Recombinant trout IL-15 preferentially stimulated splenic leukocytes from healthy fish, where it induced a large increase in IFN-γ expression, with little, if any, effect on IL-1β expression. This effect was quite long-lived, and was still apparent 24 h poststimulation. Although the exact cell types being affected have still to be determined, it is clear that once produced IL-15 will have a profound affect on the ability of the fish immune system to activate antimicrobial defenses and genes induced themselves by IFN-γ.

A novel IL-1 family member (nIL-1F) has been discovered in fish, adding a further member to this cytokine family. The unique gene organization of nIL-1F, together with its location in the genome and low homology to known family members, suggests that this molecule is not homologous to known IL-1F. Nevertheless, it contains a predicted C-terminal β-trefoil structure, an IL-1F signature region within the final exon, a potential IL-1 converting enzyme cut site, and its expression level is clearly increased following infection, or stimulation of macrophages with LPS or IL-1β. A thrombin cut site is also present and may have functional relevance. The C-terminal recombinant protein antagonized the effects of rainbow trout rIL-1β on inflammatory gene expression in a trout macrophage cell line, suggesting it is an IL-1β antagonist. Modeling studies confirmed that nIL-1F has the potential to bind to the trout IL-1RI receptor protein, and may be a novel IL-1 receptor antagonist.

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Introduction. In the United States, 19 states permit recreational use of cannabis, with 16 more permitting medical use (Marijuana Policy Project, 2021). Concerns remain about whether liberalized policies result in increased adolescent cannabis use. To date, limited evidence exists that the statewide prevalence of adolescent cannabis use increased in states with liberalized policies. However, analyses at local levels show some negative impacts. Thus, we analyzed if living in a ZIP code with a dispensary (ZCWD) was associated with adolescent cannabis use. Methods. Dispensary ZIP codes from public records were matched to self-reported ZIP codes on the Illinois Youth Survey (IYS). We compared past 30-day and past-year cannabis use among youth living in a ZCWD and not living in a ZCWD. Results. About one in eight adolescents (12.8%, n = 1,348) in the weighted sample (n=10,569) resided in a ZCWD. Overall, past 30-day use was lower among youth who lived in ZIP codes with dispensaries (OR = .69, p < .05), with variation by grade. For example, only 10th (OR = .62, p < .05) and 12th graders (OR = .59, p < .05) living in a ZCWD had lower odds of past 30-day cannabis use. Additionally, only 12th graders in a ZCWD had lower odds of past-year use (OR = .70, p < .05). Finally, suburban youth living in a ZCWD also had lower odds of cannabis use (OR = .54, p < .01). Conclusion/Discussion. Cannabis use was significantly lower among 10th and 12th graders living in a ZCWD. Additional research should continue to monitor evolving state policies and whether they are associated with adolescent cannabis use.