Decoding Toll-like receptors: Recent insights and perspectives in innate immunity.

Toll-like receptors (TLRs) are an evolutionarily conserved family in the innate immune system and are the first line of host defense against microbial pathogens by recognizing pathogen-associated molecular patterns (PAMPs). TLRs, categorized into cell surface and endosomal subfamilies, recognize diverse PAMPs, and structural elucidation of TLRs and PAMP complexes has revealed their intricate mechanisms. TLRs activate common and specific signaling pathways to shape immune responses.

Alveolar macrophages instruct CD8 T cell expansion by antigen cross-presentation in lung.

Lung CD8 memory T cells play central roles in protective immunity to respiratory viruses, such as influenza A virus (IAV). Here, we find that alveolar macrophages (AMs) function as antigen-presenting cells that support the expansion of lung CD8 memory T cells. Intranasal antigen administration to mice subcutaneously immunized with antigen results in a rapid expansion of antigen-specific CD8 T cells in the lung, which is dependent on antigen cross-presentation by AMs.

Antigen Presentation in the Lung.

The lungs are constantly exposed to environmental and infectious agents such as dust, viruses, fungi, and bacteria that invade the lungs upon breathing. The lungs are equipped with an immune defense mechanism that involves a wide variety of immunological cells to eliminate these agents. Various types of dendritic cells (DCs) and macrophages (MACs) function as professional antigen-presenting cells (APCs) that engulf pathogens through endocytosis or phagocytosis and degrade proteins derived from them into peptide fragments.

Regulation of expression by single CpG methylation in downstream of transcription initiation site.

The innate immune system is an immediate defense against infectious pathogens by the production of inflammatory cytokines and other mediators. Deficiencies of epigenetic regulatory enzymes, such as and , cause dysregulation of cytokine expression. However, it is unclear if DNA methylation at a single CpG dinucleotide in a specific gene locus can regulate gene expression.