Macrophages: These are large phagocytic cells derived from monocytes. They are present in tissues and can engulf and digest pathogens and cellular debris.
Neutrophils: These are the most abundant type of white blood cells and are among the first to arrive at the site of infection. They also perform phagocytosis.
Dendritic Cells: These cells act as antigen-presenting cells and bridge the innate and adaptive immune responses by processing and presenting antigens to T cells.
Natural Killer Cells: These cells can recognize and kill infected or cancerous cells without the need for prior activation.
Phagocytosis: Cells like macrophages and neutrophils engulf and digest pathogens.
Inflammation: The release of cytokines and chemokines leads to increased blood flow and the recruitment of immune cells to the site of infection.
Complement System: This is a group of proteins that can directly kill pathogens or mark them for destruction by other immune cells.
Antimicrobial Peptides: These are small proteins that can directly kill bacteria, fungi, and viruses.
Increased cellularity at the site of infection, primarily due to the influx of neutrophils and macrophages.
Presence of
edema due to increased vascular permeability.
Vasodilation and congestion of blood vessels.
Formation of
pus, which is an accumulation of dead neutrophils, dead pathogens, and cellular debris.
Conclusion
The innate immune response is a vital component of the body's defense mechanism, offering a rapid and non-specific reaction to pathogens. Understanding the histological features and cellular players involved provides a comprehensive view of how the body initially combats infection and sets the stage for the adaptive immune response.
