Answer: Pathogens such as bacteria, viruses, and certain parasites can enter host cells through processes like phagocytosis, endocytosis, or by binding to sIg. These mechanisms allow the pathogens to invade and manipulate the host cell for their own survival and replication.
Step-by-step explanation:
Pathogens that can enter the cell via phagocytosis, endocytosis, or sIg (secretory immunoglobulin) binding include:
1) Bacteria: Some bacteria can be engulfed by immune cells, such as macrophages and neutrophils, through a process called phagocytosis. These immune cells recognize the bacteria as foreign and engulf them into vesicles called phagosomes. Examples of bacteria that can be phagocytosed include Escherichia coli and Staphylococcus aureus.
2) Viruses: Some viruses can enter host cells through endocytosis. Endocytosis is a cellular process where cells engulf external materials and bring them into the cell. Once inside the cell, the virus escapes the endosome and releases its genetic material to hijack the host cell's machinery for replication. Examples of viruses that can enter cells through endocytosis include influenza virus and human immunodeficiency virus (HIV).
3) Certain parasites: Some parasites can enter cells through endocytosis or by binding to sIg. For example, the malaria parasite Plasmodium falciparum enters red blood cells through endocytosis, allowing the parasite to survive and replicate within the host cell. Similarly, certain parasitic protozoa can bind to sIg, which is present on the surface of epithelial cells, to gain entry into the cells and establish infection.