Innate Immunity:
* Pattern Recognition Receptors (PRRs): These receptors, located on various immune cells, recognize and bind to pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs). PAMPs are molecules found on pathogens, while DAMPs are released from damaged cells. This binding triggers an immune response.
* Natural Killer (NK) Cells: These cells kill virus-infected and cancerous cells without prior sensitization. They recognize and destroy cells lacking MHC I, a surface molecule that distinguishes healthy cells.
* Macrophages and Neutrophils: These phagocytic cells engulf and destroy pathogens and cellular debris.
* Interferons (IFNs): These proteins are released by infected cells to interfere with viral replication and activate other immune cells.
Adaptive Immunity:
* T Lymphocytes (T Cells): These cells are responsible for cell-mediated immunity.
* Cytotoxic T Cells (CTLs): These cells directly kill infected or cancerous cells by releasing cytotoxic substances.
* Helper T Cells (Th Cells): These cells help activate other immune cells like B cells and macrophages.
* B Lymphocytes (B Cells): These cells are responsible for humoral immunity. They produce antibodies that bind to specific antigens on pathogens, neutralizing them or tagging them for destruction.
Intracellular Defense Mechanisms:
* Autophagy: A cellular process that degrades damaged organelles and pathogens within the cell.
* Inflammasomes: Multiprotein complexes that activate the inflammatory response in response to pathogens or cell stress.
Other Factors:
* MHC Molecules: Major histocompatibility complex molecules present antigens to T cells, initiating an immune response.
* Complement System: A group of proteins that can directly kill pathogens or help activate other immune cells.
Overall, a complex interplay of these components provides a multi-layered defense system against threats within living cells, effectively tackling abnormal cells and pathogens.
