What does Macrophage do after it ingests a pathogen?

After ingesting a pathogen, a macrophage undergoes a series of cellular processes to break down and eliminate the invading microorganism. The sequence of events typically involves the following steps:

1. Phagocytosis: The macrophage extends its pseudopodia and engulfs the pathogen, forming a phagosome, a membrane-bound vesicle containing the ingested material.

2. Phagosome-lysosome fusion: The phagosome then fuses with a lysosome, a membrane-bound organelle containing various degradative enzymes and antimicrobial substances. This fusion creates a phagolysosome, an acidic compartment where the pathogen is exposed to a harsh environment.

3. Killing and digestion: Within the phagolysosome, the pathogen is subjected to a variety of degradative processes. Lysosomal enzymes, such as proteases, lipases, and nucleases, break down the pathogen's proteins, lipids, and nucleic acids. Antimicrobial peptides and reactive oxygen species (ROS) produced by the macrophage further contribute to killing the pathogen.

4. Antigen presentation: During the degradation process, the macrophage fragments and processes the pathogen's antigens, which are small molecules that can be recognized by the immune system. These processed antigens are then displayed on the macrophage's cell surface in association with major histocompatibility complex (MHC) molecules. This presentation of antigens allows other immune cells, such as T lymphocytes, to recognize and respond to the pathogen.

5. Effector functions: Once activated by the presented antigens, T lymphocytes and other immune cells can elicit various effector functions to further eliminate the pathogen. This can include the release of cytokines and chemokines, which recruit additional immune cells to the site of infection, as well as the direct killing of infected cells.

6. Clearance: After the pathogen has been degraded, the remnants and cellular debris are eventually removed by the macrophage through exocytosis or other cellular processes. This helps to clear the infection and restore tissue homeostasis.

The ability of macrophages to ingest, kill, and process pathogens is essential for the body's defense against infections. These cells play a critical role in both innate and adaptive immune responses, acting as the first line of defense against invading microorganisms and initiating subsequent immune responses to eliminate the infection.