Antigens and Phagocytosis

Antigen

• Foreign protein that stimulates an immune response

Types of antigen presenting cells

All these cells will trigger an immune response (activate T cells)

• Phagocyte with pathogen antigens on its surface

• A cancerous cell has different antigens to a non cancerous cell

• A cell infected by a virus presents some of the viral antigens on its surface

• A transplanted cell will have different antigens

Specific Immune responses

• Slower and specific to each pathogen

• Antibody production (humoral response) and cell-mediated response by T lymphocytes (T-Cells)

Non-specific Immune Responses

• Immediate and same for all pathogens

• Barriers e.g. skin and scabs

• Phagocytosis
  

Phagocytes

• Phagocytes are a type of cell that engulf and can digest other cells

• 2 types of phagocytes are macrophages and neutophils, which are both essential cells involved in immunity

Phagocytosis

• Phagocyte engulfs the pathogen to form a phagosome

• Lysosomes fuse with this phagosome forming a phagolysosome

• The fused lysosomes release their lysozymes into the phagolysosome

• The lyoszymes digest the pathogen

• Antigens from the pathogen are displayed on the cell membrane of the phagocyte