Bovine Interleukin-10 (IL-10) is a potent anti-inflammatory cytokine produced primarily by regulatory T cells (Tregs), Th2 cells, macrophages, dendritic cells, and certain B-cell subsets in cattle (Bos taurus), where it plays a central role in limiting excessive immune activation and maintaining immune homeostasis. IL-10 signals through the IL-10 receptor complex (IL-10R1/IL-10R2), activating JAK/STAT3 pathways that suppress pro-inflammatory cytokine production (including IL-1β, TNF-α, and IL-12), reduce antigen presentation capacity, and downregulate Th1-type immune responses. In bovine health, IL-10 is critically involved in modulating immune responses during chronic and economically significant infections such as bovine viral diarrhea virus (BVDV), Mycobacterium avium subsp. paratuberculosis (Johne’s disease), Mycobacterium bovis (bovine tuberculosis), mastitis, and parasitic infections, where elevated IL-10 expression can contribute to immune suppression and pathogen persistence. While IL-10 helps prevent tissue damage from excessive inflammation, dysregulated or sustained IL-10 production may impair protective cell-mediated immunity. As a biomarker of immune regulation, bovine IL-10 is important in vaccine evaluation, disease progression studies, and assessment of Th1/Th2 immune balance. In veterinary and comparative research, characterization of bovine IL-10 supports investigations into host–pathogen interactions, immune tolerance mechanisms, chronic infection dynamics, and development of immunomodulatory strategies to improve cattle health, productivity, and disease resilience.