Question

Diagram and describe the phagocytosis, destruction, and antigen presentation that occur when a macrophage ingests a bacterium

Answer 1

• Phagocytosis is the ingestion of invading foreign particles, such as bacteria by individual cell. phagocytosis is enhanced by variety of factors called opsonins. Many specialized cell types like neutrophils ,macrophages, monocytes, natural killer cells. Phagocytosis is a protective mechanism carried out by these cell types. In phagocytosis antigens are intralized by these cells and then kill within the cell. If antigen is smaller in size then cells go under phagocytosis and if Ag is larger in size then cells go for ADCC ( antibody dependent cell mediated cytotoxicity)
• Antigen presentation is the process by which protein antigen is presented to lymphocytes in the form of short peptides. Antigen presentation is associated with antigen presenting molecules such as MHC class I and class II on the surface of antigen presenting cells ( APCs). T -cell receptora does not recognize free antigens. T -cell receptor recognize only antigen when bound to MHC molecules. CD4 TH cells recognize MHC I and CD8 cells recognize MHC II molecules.
• The events involved in the generation of peptide antigens from proteins inside cells, the binding of peptides to MHC molecules , and the display of peptide- MHC complexes on the surface for T- cell recognition are collectively as Antigen presentation.