The camelid-derived single chain antibody (sdAb), also termed VHH or nanobody, is a unique, functional heavy (H)-chain antibody (HCAb). In contrast to conventional antibodies, sdAb is a unique antibody fragment consisting of a heavy-chain variable domain. It lacks light chains and a first constant domain (CH1). With a small molecular weight of only 12~15 kDa, sdAb has a similar antigen-binding affinity to conventional Abs but a higher solubility, which exerts unique advantages for the recognition and binding of functional, versatile, target-specific antigen fragments. In recent decades, with their unique structural and functional features, nanobodies have been considered promising agents and alternatives to traditional monoclonal antibodies. As a new generation of nano-biological tools, natural and synthetic nanobodies have been used in many fields of biomedicine, including biomolecular materials, biological research, medical diagnosis and immune therapies. This article briefly overviews the biomolecular structure, biochemical properties, immune acquisition and phage library construction of nanobodies and comprehensively reviews their applications in medical research. It is expected that this review will provide a reference for the further exploration and unveiling of nanobody properties and function, as well as a bright future for the development of drugs and therapeutic methods based on nanobodies.

Clinical mastitis (CM) is a prevalent and severe inflammatory disease in dairy cows affecting the mammary glands. Fatty acid (FA) metabolism and associated enzymes are crucial for many physiological and pathological processes in dairy cows. However, the relationships among FA metabolism, FA-associated enzymes, and CM, as well as the mechanisms underlying their interactions, in dairy cows are not fully understood. The aim of this study was to characterize biological process (BP) terms, pathways, and differentially expressed proteins (DEPs) related to FA metabolism from our previous data-independent acquisition proteomic study. Six BPs involving 14 downregulated and 20 upregulated DEPs, and four pathways involving 10 downregulated and 11 upregulated DEPs related to FA synthesis and metabolism were systematically identified. Associated analysis suggested that 12 candidate DEPs obtained from BPs and pathways, especially acyl-CoA thioesterase 7 (ACOT7), regulate long-chain FA (LCFA) elongation and the biosynthesis of unsaturated FAs. Immunohistochemical and immunofluorescence staining results showed that ACOT7 was present mainly in the cytoplasm of mammary epithelial cells. The qRT-PCR and Western blotting results showed that ACOT7 mRNA and protein levels in the mammary glands of the CM group were significantly upregulated compared to those in the healthy group. This evidence indicates that ACOT7 is positively correlated with CM onset and progression in Holstein cows. These findings offer novel insights into the role of FA metabolism and related enzymes in CM and offer potential targets for the development of therapeutic strategies and biomarkers for the prevention and treatment of CM in dairy cows.

Astragalus membranaceus (AM) has been reported to support immune function, but its epigenetic mechanism on immune restoration of cyclophosphamide (CTX)-induced immunosuppression remains unclear. To evaluate the recovery of immune function, we assessed the injury of splenic pathology, cytokines levels in serum, proportional changes in CD4⁺ and CD8⁺ T cells, and the recall response of Hspx-specific T cell. In addition, to define the underlying epigenetic regulatory mechanism, we measured the expression levels of DNA methyltransferases (Dnmt1, Dnmt3a and Dnmt3b) and the methylation status of the Carnitine palmitoyltransferase 1A (Cpt1a) gene. The results showed that the crude extract of AM repaired the immunosuppression induced by CTX. This is reflected in the alleviation of splenic pathological injury, the elevated proportions of CD4⁺ and CD8⁺ T cells, and the increased levels of serum IL-2 and IFN-γ. The crude extract of AM also enhanced the recall response of Hspx-specific CD8⁺ T cells; that is, the frequencies of the resulting IL-2⁺ and IFN-γ⁺ cells were significantly higher than those in the CTX + Vaccine group. All these results indicate that the adaptive immune response induced by the crude extract of AM is significantly enhanced. On the other hand, AM crude extract reversed the CTX-induced downregulation of Dnmt3a mRNA and restored CpG methylation of Cpt1a gene to a level comparable to the vaccine group at molecular level. Consistent with the elevated CpG methylation, CTX-induced upregulation of Cpt1a mRNA was also reduced. These findings reveal that AM extract enhances the antigen-specific functional recall responses of CD8⁺ T cells in immunosuppressed mice were associated with Cpt1a gene methylation, thereby establishing a translational link between traditional herbal medicine and modern epigenetics.