CD6 deficiency impairs early immune response to bacterial sepsis

CD6 in Human Disease

CD6 is a cell surface protein expressed by T cells, a subset of NK cells, a small population of B cells, and thymocytes. CD6 has multiple and complex functions due to its distinct functional epitopes that mediate interactions with several ligands including CD166 (ALCAM) and CD318 (CDCP1). An additional molecule, CD44, is being investigated as a potential new ligand of CD6. CD6 plays critical roles in lymphocyte activation, proliferation, and adhesion to antigen-presenting, epithelial, and cancer cells. CD6 is a risk gene for multiple autoimmune diseases, possibly related to its numerous roles in regulating CD4+T-cell responses. Additionally, CD6 is a potential target for cancer immunotherapy. Here, we dissect the role of CD6 in the pathogenesis of more than 15 diseases and discuss recent data supporting the use of CD6-targeted therapy in humans.

In Vitro Analysis of Tandem Peptides from Human CD5 and CD6 Scavenger Receptors as Potential Anti-Cryptococcal Agents

Cryptococcus neoformans is included in the World Health Organization fungal priority pathogen list, complied to expedite improved research and public-health interventions. The limited number of available antifungal drugs, their associated toxicity, and the emergence of drug-resistant strains make the development of new therapeutic strategies mandatory. Pattern-recognition receptors (PRRs) from the host's innate immune system constitute a potential source of new antimicrobial agents. CD5 and CD6 are lymphoid members of the ancient scavenger receptor cysteine-rich superfamily (SRCR-SF) which bind pathogen-associated molecular patterns (PAMPs) of fungal and bacterial origin. Evidence supports the concept that such binding maps to 11-mer sequences present in each of their three SRCR extracellular domains. Herein, we have designed synthetic peptides containing tandems of such 11-mer sequences (namely CD5-T and CD6-T) and analyzed their C. neoformans-binding properties in vitro. Our results show both inhibitory effects on fungal growth and an ability to impact capsule formation and titanization, two critical virulence factors of C. neoformans involved in immune evasion. These effects hold promise for CD5-T and CD6-T peptides as single or adjuvant therapeutic agents against cryptococcosis.

Controllable Preparation and Research Progress of Photosensitive Antibacterial Complex Hydrogels

Hydrogels are materials consisting of a network of hydrophilic polymers. Due to their good biocompatibility and hydrophilicity, they are widely used in biomedicine, food safety, environmental protection, agriculture, and other fields. This paper summarizes the typical complex materials of photocatalysts, photosensitizers, and hydrogels, as week as their antibacterial activities and the basic mechanisms of photothermal and photodynamic effects. In addition, the application of hydrogel-based photoresponsive materials in microbial inactivation is discussed, including the challenges faced in their application. The advantages of photosensitive antibacterial complex hydrogels are highlighted, and their application and research progress in various fields are introduced in detail.

Single-cell and spatiotemporal transcriptomic analyses reveal the effects of microorganisms on immunity and metabolism in the mouse liver

The gut-liver axis is a complex bidirectional communication pathway between the intestine and the liver in which microorganisms and their metabolites flow from the intestine through the portal vein to the liver and influence liver function. In a sterile environment, the phenotype or function of the liver is altered, but few studies have investigated the specific cellular and molecular effects of microorganisms on the liver. To this end, we constructed single-cell and spatial transcriptomic (ST) profiles of germ-free (GF) and specific-pathogen-free (SPF) mouse livers. Single-cell RNA sequencing (scRNA-seq) and single-nucleus RNA sequencing (snRNA-seq) revealed that the ratio of most immune cells was altered in the liver of GF mice; in particular, natural killer T (NKT) cells, IgA plasma cells (IgAs) and Kupffer cells (KCs) were significantly reduced in GF mice. Spatial enhanced resolution omics sequencing (Stereo-seq) confirmed that microorganisms mediated the accumulation of Kupffer cells in the periportal zone. Unexpectedly, IgA plasma cells were more numerous and concentrated in the periportal vein in liver sections from SPF mice but less numerous and scattered in GF mice. ST technology also enables the precise zonation of liver lobules into eight layers and three patterns based on the gene expression level in each layer, allowing us to further investigate the effects of microbes on gene zonation patterns and functions. Furthermore, untargeted metabolism experiments of the liver revealed that the propionic acid levels were significantly lower in GF mice, and this reduction may be related to the control of genes involved in bile acid and fatty acid metabolism. In conclusion, the combination of sc/snRNA-seq, Stereo-seq, and untargeted metabolomics revealed immune system defects as well as altered bile acid and lipid metabolic processes at the single-cell and spatial levels in the livers of GF mice. This study will be of great value for understanding host-microbiota interactions.

Experimental and genetic evidence for the impact of CD5 and CD6 expression and variation in inflammatory bowel disease

Crohn’s disease (CD) and ulcerative colitis (UC) are inflammatory bowel diseases (IBD) resulting from the interaction of multiple environmental, genetic and immunological factors. CD5 and CD6 are paralogs encoding lymphocyte co-receptors involved in fine-tuning intracellular signals delivered upon antigen-specific recognition, microbial pattern recognition and cell adhesion. While CD5 and CD6 expression and variation is known to influence some immune-mediated inflammatory disorders, their role in IBD remains unclear. To this end, Cd5- and Cd6-deficient mice were subjected to dextran sulfate sodium (DSS)-induced colitis, the most widely used experimental animal model of IBD. The two mouse lines showed opposite results regarding body weight loss and disease activity index (DAI) changes following DSS-induced colitis, thus supporting Cd5 and Cd6 expression involvement in the pathophysiology of this experimental IBD model. Furthermore, DNA samples from IBD patients of the ENEIDA registry were used to test association of CD5 (rs2241002 and rs2229177) and CD6 (rs17824933, rs11230563, and rs12360861) single nucleotide polymorphisms with susceptibility and clinical parameters of CD (n=1352) and UC (n=1013). Generalized linear regression analyses showed association of CD5 variation with CD ileal location (rs2241002^CC) and requirement of biological therapies (rs2241002^C-rs2229177^T haplotype), and with poor UC prognosis (rs2241002^T-rs2229177^T haplotype). Regarding CD6, association was observed with CD ileal location (rs17824933^G) and poor prognosis (rs12360861^G), and with left-sided or extensive UC, and absence of ankylosing spondylitis in IBD (rs17824933^G). The present experimental and genetic evidence support a role for CD5 and CD6 expression and variation in IBD’s clinical manifestations and therapeutic requirements, providing insight into its pathophysiology and broadening the relevance of both immunomodulatory receptors in immune-mediated disorders.